Background: Patellofemoral Malalignment versus Tissue Homeostasis

IntroductionAnterior knee paina is the most common kneecomplaint seen in adolescents and young adults,in both the athletic and nonathletic population,although in the former, its incidence is higher.The rate is around 9% in young active adults.69

Its incidence is 5.4% of the total injuries and ashigh as a quarter of all knee problems treated ata sports injury clinic.16 Nonetheless, I am con-vinced that not all cases are diagnosed and hencethe figure is bound to be even higher.Furthermore, it is to be expected that the num-ber of patients with this complaint will increasebecause of the increasing popularity of sportpractice. On the other hand, a better under-standing of this pathology by orthopedic sur-geons and general practitioners should lead tothis condition being diagnosed more and morefrequently. Females are particularly predisposedto it.14 Anatomic factors such as increased pelvicwidth and resulting excessive lateral thrust onthe patella, and postural and sociological factorssuch as wearing high heels and sitting with legsadducted can influence the incidence and sever-ity of this condition in women.29 Moreover, it isa nemesis to both the patient and the treatingphysician, creating chronic disability, limitationfrom participation in sports, sick leave, and gen-erally diminished quality of life.

Special mention should be made of the term“patellar tendonitis,” closely related to anteriorknee pain. In 1998, Arthroscopy published anarticle by Nicola Maffulli and colleagues52 thatbore the title “Overuse tendon conditions: Timeto change a confusing terminology.” Very aptly,these authors concluded that the clinicalsyndrome characterized by pain (diffuse orlocalized), tumefaction, and a lower sports per-formance should be called “tendinopathy.”52 Theterms tendinitis, paratendinitis, and tendinosisshould be used solely when in possession of theresults of an excision biopsy. Therefore the per-vasive clinical diagnosis of patellar tendinitis,which has become the paradigm of overuse ten-don injuries, would be incorrect. Furthermore,biopsies in these types of pathologies do notprove the existence of chronic or acute inflam-matory infiltrates, which clearly indicate thepresence of tendinitis. Patellar tendinopathy is afrequent cause for anterior knee pain, which canturn out to be frustrating for physicians as wellas for athletes, for whom this lesion can wellmean the end of their sports career. This meansthat in this monograph we cannot leave out adiscussion of this clinical entity, which is dealtwith in depth in Chapters 15 and 16.

Finally, anterior knee pain is also a well-documented complication and the most com-mon complaint after anterior cruciate ligament(ACL) reconstruction. Because of the upsurgeof all kinds of sports, ACL injuries have becomeincreasingly common and therefore their surgical

a Term that describes pain in which the source is eitherwithin the patellofemoral joint or in the support structuresaround it.

3

1Background: Patellofemoral Malalignment versusTissue HomeostasisMyths and Truths about Patellofemoral DiseaseVicente Sanchis-Alfonso

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treatment is currently commonplace.b The inci-dence of anterior knee pain after ACL recon-struction with bone-patellar tendon-bone(B-PT-B) autografts is from 4% to 40% .24 In thissense, we must remember that the tissue mostcommonly used for ACL reconstruction, accord-ing to the last survey of the ACL Study Group(May 29–June 4, 2004, Forte Village Resort,Sardinia, Italy), is the B-PT-B.9 Moreover, ante-rior knee pain is also a common complaint,from 6% to 12.5% after 2 years, with the use ofhamstring grafts.4,11,48,65 For the reasons men-tioned above, we believe it is interesting to carryout a detailed analysis in this book of theappearance of anterior knee pain secondary toACL reconstructive surgery, underscoring theimportance of treatment, and especially, pre-vention. In order not to fall into the trap of dog-matism, the problem is analyzed by differentauthors from different perspectives (seeChapters 17 to 19).

The ProblemIn spite of its high incidence, anterior knee painsyndrome is the most neglected, the leastknown, and the most problematic pathologicalknee condition. This is why the expression“Black Hole of Orthopedics” that Stanley Jamesused to refer to this condition is extremely apt todescribe the current situation. On the otherhand, our knowledge of the causative mecha-nisms of anterior knee pain is limited, with theconsequence that its treatment is one of themost complex among the different pathologiesof the knee. As occurs with any pathologicalcondition, and this is not an exception, for thecorrect application of conservative as well asoperative therapy, it is essential to have a thor-ough understanding of the pathogenesis of thesame (see Chapters 2, 3, 4, 8, and 11). This is theonly way to prevent the all-too-frequent storiesof multiple failed surgeries and demoralizedpatients, a fact that is relatively common for theclinical entity under scrutiny in this book ascompared with other pathological processesaffecting the knee (see Chapters 20 and 21).

Finally, diagnostic errors, which can lead tounnecessary interventions, are relatively frequentin this pathologic condition. As early as 1922, inthe German literature, Georg Axhausen5 statedthat chondromalacia can simulate a meniscallesion resulting in the removal of normal menisci.In this connection, Tapper and Hoover,66 in 1969,suspected that over 20% of women who did badlyafter an open meniscectomy had a patellofemoralpathology. Likewise, John Insall,41 in 1984, statedthat patellofemoral pathology was the most com-mon cause of meniscectomy failure in youngpatients, especially women. Obviously, this fail-ure was a result of an erred diagnosis and, conse-quently, of a mistakenly indicated surgery. Atpresent, the problem of diagnostic confusion isstill the order of the day. The following datareflect this problem. In my surgical series 11% ofpatients underwent unnecessary arthroscopicmeniscal surgery, which, far from eradicating thesymptoms, had worsened them. An improvementwas obtained, however, after realignment surgeryof the extensor mechanism. Finally, 10% ofpatients in my surgical series were referred to apsychiatrist by physicians who had previouslybeen consulted.

The question we ask ourselves is: Why is thereless knowledge about this kind of pathologythan about other knee conditions? According tothe International Patellofemoral Study Group(IPSG),42 there are several explanations: (1) Thebiomechanics of the patellofemoral joint is morecomplex than that of other structures in theknee; (2) the pathology of the patella arousesless clinical interest than that of the menisci orthe cruciate ligaments; (3) there are variouscauses for anterior knee pain; (4) there is oftenno correlation between symptoms, physicalfindings, and radiological findings; (5) there arediscrepancies regarding what is regarded as“normal;” and (6) there is widespread termino-logical confusion (“the Tower of Babel”). Asregards what is considered “normal” or “abnor-mal” it is interesting to mention the work byJohnson and colleagues,45 who makes a gender-dependent analysis of the clinical assessment ofasymptomatic knees. We discuss some of theconclusions of this interesting study below.

In 1995, the prevailing confusion led to thefoundation by John Fulkerson of the UnitedStates and Jean-Yves Dupont of France of theIPSG in order to advance in the knowledge ofthe patellofemoral joint disorders by intercul-tural exchange of information and ideas. The

4 Etiopathogenic Bases and Therapeutic Implications

b In the general population, an estimated one in 3000 indi-viduals sustains an ACL injury per year in the UnitedStates,37 corresponding to an overall injury rate of approxi-mately 80,00032 to 100,00037 injuries annually. The highestincidence is in individuals 15 to 25 years old who participatein pivoting sports.32

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condition is of such high complexity that evenwithin this group there are antagonisticapproaches and theories often holding dogmaticpositions. Moreover, to stimulate researchefforts and education regarding patellofemoralproblems John Fulkerson created in 2003 thePatellofemoral Foundation. The PatellofemoralFoundation sponsors the “PatellofemoralResearch Excellence Award” to encourageoutstanding research leading to improvedunderstanding, prevention, and treatment ofpatellofemoral pain or instability. I want toemphasize the importance to improve preven-tion and diagnosis in order to reduce theeconomic and social costs of this pathology(see Chapters 6, 8, and 17). Moreover thisfoundation sponsors the “PatellofemoralTraveling Fellowship” to promote better under-standing and communication regarding patello-femoral pain, permitting visits to several centers,worldwide, that offer opportunities to learnabout the complexities of patellofemoral pain.

This chapter provides an overview of the mostimportant aspects of etiopathogenesis of ante-rior knee pain and analyzes some myths andtruths about patellofemoral disease.

Historical Background: InternalDerangement of the Knee andChondromalacia Patellae; ActualMeaning of Patellar Chondral InjuryAnterior knee pain in young patients has histor-ically been associated with the terms “internalderangement of the knee” and “chondromalaciapatellae.” In 1986, Schutzer and colleagues63 pub-lished a paper in the Orthopedic Clinics of NorthAmerica about the CT-assisted classification ofpatellofemoral pain. The authors of that paperhighlight the lack of knowledge that besets thisclinical entity when they associate the initials ofinternal derangement of the knee (IDK) withthose of the phrase “I Don’t Know,” and those ofchondromalacia patellae (CMP) with those of“Could be – May be – Possibly be.” Although wethink that nowadays this is certainly an exagger-ation, it is true that the analogy helps us under-score the controversies around this clinicalentity, or at least draw people’s attention to it.

The expression “internal derangement of theknee” was coined in 1784 by British surgeonWilliam Hey.50 This term was later discredited bythe German school surgeon Konrad Büdinger, Dr.Billroth’s assistant in Vienna, who in 1906

described fissuring and degeneration of the patel-lar articular cartilage of spontaneous origin,7 andin 1908 in another paper described similar lesionsof traumatic origin.8 Although Büdinger was thefirst to describe chondromalacia, this term wasnot used by Büdinger himself. Apparently it wasKoenig who in 1924 used the term “chondroma-lacia patellae” for the first time, although accord-ing to Karlson this term had already been used inAleman’s clinic since 1917.1,28 What does seemclear is that it was Koenig who popularized theterm. Büdinger considered that the expression“internal derangement of the knee” was a“wastebasket” term. And he was right since theexpression lacks any etiological, therapeutic, orprognostic implication.

Until the end of the 1960s anterior knee painwas attributed to chondromalacia patellae.Stemming from the Greek chondros and malakia,this term translates literally as “softened patellararticular cartilage.” However, in spite of the factthat the term “chondromalacia patellae” has his-torically been associated with anterior knee pain,many authors have failed to find a connectionbetween both.12,49,59 In 1978, Leslie and Bentleyreported that only 51% of patients with a clinicaldiagnosis of chondromalacia had changes on thepatellar surface when were examined byarthroscopy.49 In 1991, Royle and colleagues59

published in Arthroscopy a study in which theyanalyzed 500 arthroscopies performed in a 2-yearperiod, with special reference made to thepatellofemoral joint. In those patients with painthought to be arising from this joint, 63% had“chondromalacia patellae” compared with a 45%incidence in those with meniscal pathologicalfindings at arthroscopy. They concluded thatpatients with anterior knee pain do not alwayshave patellar articular changes, and patellarpathology is often asymptomatic (Figure 1.1).In agreement with this, Dye18 did not feel anypain during arthroscopic palpation of his exten-sive lesion of the patellar cartilage withoutintraarticular anesthesia. In this regard it wouldbe remembered that the articular cartilage isdevoid of nerve fibers and, therefore, cannot hurt.

Surgeons often refer to patellar cartilagechanges as chondromalacia, using poor definedgrades. According to the IPSG42 we should use theterm chondral or cartilage lesion, and rather thanresorting to grades in a classification, providing aclear description of the injury (e.g., appearance,depth, size, location, acute vs. chronic clinical sta-tus). Although hyaline cartilage cannot be the

Background: Patellofemoral Malalignment versus Tissue Homeostasis 5

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source of pain in itself, damage of articular carti-lage can lead to excessive loading of the subchon-dral bone, which, due to its rich innervation,could be a potential source of pain. Therefore, apossible indication for very selected cases couldbe a resurfacing procedure such as mosaicplasty(see Chapter 12) or periostic autologous trans-plants (see Chapter 13).

According to the IPSG,42 the term chondro-malacia should not be used to describe a clinicalcondition; it is merely a descriptive term formorphologic softening of the patellar articularcartilage. In conclusion, this is a diagnosis thatcan be made only with visual inspection and pal-pation by open or arthroscopic means and it is

irrelevant. In short, chrondromalacia patellae isnot synonymous with patellofemoral pain.Thus, the term chondromalacia, is also, usingBüdinger’s own words, a wastebasket term as itis lacking in practical utility. In this way, the fol-lowing ominous 1908 comment from Büdingerabout “internal derangement of the knee” couldbe applied to chondromalacia:22 “[It] will simplynot disappear from the surgical literature. It isthe symbol of our helplessness in regards to adiagnosis and our ignorance of the pathology.”

Although I am aware of the fact that traditionsdie hard, the term “chondromalacia patellae”should be excluded from the clinical terminol-ogy of current orthopedics for the reasons I haveexpressed. Almost one century has elapsed andthis term is still used today, at least in Spain, byclinicians, by the staff in charge of codifying thedifferent pathologies for our hospitals’ data-bases, as well as by private health insurers’ listsof covered services.

Patellofemoral MalalignmentIn the 1970s anterior knee pain was related to thepresence of patellofemoral malalignment (PFM).c

In 1968, Jack C. Hughston (Figure 1.2) publishedan article on subluxation of the patella, whichrepresented a major turning point in the recogni-tion and treatment of patellofemoral disorders.35

In 1974, Al Merchant, in an attempt to betterunderstand patellofemoral biomechanics, intro-


Figure 1.2. Jack C. Hughston, MD (1917–2004). One of the foundingfathers of Sports Medicine. (Reproduced with permission from the Journal ofAthletic Training, 2004; 39: 309.)

c We define PFM as an abnormality of patellar tracking thatinvolves lateral displacement or lateral tilt of the patella, orboth, in extension, that reduces in flexion.

Figure 1.1. The intensity of preoperative pain is not related to the seri-ousness or the extension of the chondromalacia patellae found duringsurgery. The most serious cases of chondromalacia arise in patients witha recurrent patellar dislocation who feel little or no pain between theirdislocation episodes (a). Chondral lesion of the patella with fragmenta-tion and fissuring of the cartilage in a patient with PFM that consulted foranterior knee pain (b).

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duced the axial radiograph of the patellofemoraljoint.54 The same author suggested, also in 1974,the lateral retinacular release as a way of treatingrecurrent patellar subluxation.55 In 1975, PaulFicat, from France, popularized the concept ofpatellar tilt, always associated with increasedtightness of the lateral retinaculum, which causedexcessive pressure on the lateral facet of thepatella, leading to the “lateral patellar compres-sion syndrome” (“Syndrome d’HyperpressionExterne de la Rotule”).21 According to Ficat lateralpatellar compression syndrome would causehyperpressure in the lateral patellofemoral com-partment and hypopressure in the medialpatellofemoral compartment. Hypopressure andthe disuse of the medial patellar facet would causemalnutrition and early degenerative changes inthe articular cartilage because of the lack of nor-mal pressure and function. This may explain whyearly chondromalacia patellae is generally foundin the medial patellar facet. Hyperpression alsowould favor cartilage degeneration, which mightexplain the injury of the lateral facet. Two yearslater, in 1977, Ficat and Hungerford22 publishedDisorders of the Patellofemoral Joint, a classic ofknee extensor mechanism surgery and the firstbook in English devoted exclusively to the exten-sor mechanism of the knee. In the preface of thebook these authors refer to the patellofemoraljoint as “the forgotten compartment of the knee.”This shows what the state of affairs was in thosedays. In fact, before the 1970s only two diagnoseswere used relating to anterior knee pain or patel-lar instability: chondromalacia patellae andrecurrent dislocation of the patella. What is more,the initial designs for knee arthroplasties ignoredthe patellofemoral joint. In 1979, John Insall pub-lished a paper on “patellar malalignment syn-drome”38 and his technique for proximal patellarrealignment, used to treat this syndrome.39

According to Insall lateral loading of the patella isincreased in malalignment syndrome. In somecases, this causes chondromalacia patellae, but itdoes not necessarily mean that chondromalacia isthe cause of pain.41 In this way, in 1983 Insall andcolleagues reported that anterior knee pain corre-lates better to malalignment rather than with theseverity of chondromalacia found during sur-gery.40 Fulkerson and colleagues have alsoemphasized the importance of PFM and exces-sively tight lateral retinaculum as a source ofanterior knee pain.25,26,63 Finally, in 2000, RonaldGrelsamer,31 from the IPSG, stated that malalign-ment appears to be a necessary but not sufficient

condition for the onset of anterior knee pain.d

According to Grelsamer,31 pain seems to be setoff by a trigger (i.e., traumatism). In this sense,Grelsamer30 tells his patients that “people withmalaligned knees are akin to someone riding abicycle on the edge of a cliff. All is well untila strong wind blows them off the cliff, which mayor may not ever happen.” Although it is morecommon to use the term malalignment as a mal-position of the patella on the femur some authors,as Robert A Teitge, from the IPSG, use the termmalalignment as a malposition of the knee jointbetween the body and the foot with the subse-quent effect on the patellofemoral mechanics (seeChapter 11).

In a previous paper61 we postulated that PFM,in some patients with patellofemoral pain, pro-duces a favorable environment for the onset ofsymptoms, and neural damage would be themain “provoking factor” or “triggering factor.”Overload or overuse may be another triggeringfactor. In this sense, in our surgical experience,we have found that in patients with symptoms inboth knees, when the more symptomatic knee isoperated on, the symptoms in the contralateralless symptomatic malaligned knee disappear ordecrease in many cases, perhaps because we havereduced the load in this knee; that is, it allows usto restore joint homeostasis. In this connection,Thomee and colleagues suggested that chronicoverloading and temporary overuse of thepatellofemoral joint, rather than malalignment,contribute to patellofemoral pain.68

For many years, PFM has been widelyaccepted as an explanation for the genesis ofanterior knee pain and patellar instability in theyoung patient. Moreover, this theory had a greatinfluence on orthopedic surgeons, who devel-oped several surgical procedures to “correct themalalignment.” Unfortunately, when PFM wasdiagnosed it was treated too often by means ofsurgery. A large amount of surgical treatmentshas been described, yielding extremely variableresults. Currently, however, the PFM concept isquestioned by many, and is not universallyaccepted to account for the presence of anteriorknee pain and/or patellar instability.


d However, many patients with patellofemoral pain have noevidence of malalignment, whatsoever.68 Therefore if PFM isa necessary condition for the presence of patellofemoralpain, how could patellofemoral pain be occurring in patientswithout malalignment?

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At present, most of the authors agree thatonly a small percentage of patients withpatellofemoral pain have truly malalignmentand are candidates for surgical correction ofmalalignment for resolution of symptoms. Infact, the number of realignment surgeries hasdropped dramatically in recent years, due toa reassessment of the paradigm of PFM.Moreover, we know that such procedures are,in many cases, unpredictable and even danger-ous; they may lead to reflex sympathetic dys-trophy, medial patellar dislocations, andiatrogenous osteoarthrosis (see Chapters 20and 21). We should recall here a phrase by doc-tor Jack Hughston, who said: “There is noproblem that cannot be made worse by sur-gery” (see Chapters 20 to 23). Among problemswith the knee, this statement has never beenmore relevant than when approaching theextensor mechanism. Therefore, we mustemphasize the importance of a correct diagno-sis (see Chapters 6 and 7) and nonoperativetreatment (see Chapters 9 and 10).

CriticismThe great problem of the PFM concept is that notall malalignments, even of significant propor-tions, are symptomatic. Even more, one kneemay be symptomatic and the other not, eventhough the underlying malalignment is entirelysymmetrical (Figure 1.3). On the other hand,

patients with normal patellofemoral alignmenton computed tomography (CT) can also sufferfrom anterior knee pain (Figure 1.4). Therefore,PFM cannot explain all the cases of anterior kneepain, so other pathophysiological processes mustexist. Moreover, PFM theory cannot adequatelyexplain the variability of symptoms experiencedby patients with anterior knee pain syndrome.

Finally, we must also remember that it has beendemonstrated that there are significant differ-ences between subchondral bone morphologyand geometry of the articular cartilage surface ofthe patellofemoral joint, both in the axial andsagittal planes6 (Figure 1.5). Therefore, a radi-ographical PFM may not be real and it couldinduce us to indicate a realignment surgery thancould provoke involuntarily an iatrogenic PFMleading to a worsening of preoperative symptoms.This would be another point against the universalacceptance of the PFM theory. Moreover, thiscould explain also the lack of predictability ofoperative results of realignment surgery.

Critical Analysis of Long-term Follow-upof Insall’s Proximal Realignment forPFM: What Have We Learned?In agreement with W.S. Halsted, I think that theoperating room is “a laboratory of the highestorder.” As occurs with many surgical techniques,and realignment surgery is not an exception,


Figure 1.3. CT at 0° from a patient with anterior knee pain and functional patellofemoral instability in the right knee; however, the left knee iscompletely asymptomatic. In both knees the PFM is symmetric.

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Figure 1.4. CT at 0° from a patient with severe anterior knee pain and patellofemoral instability in the left knee (a). This knee, which was operatedon two years ago, performing an Insall’s proximal realignment, was very symptomatic in spite of the correct patellofemoral congruence. Fulkersontest for medial subluxation was positive. Nevertheless, the right knee was asymptomatic despite the PFM. Conventional radiographs were normaland the patella was seen well centered in the axial view of Merchant (b). Axial stress radiograph of the left knee (c) allowed us to detect an iatro-genic medial subluxation of the patella (medial displacement of 15 mm). Note axial stress radiograph of the right knee (d). The symptomatologydisappeared after surgical correction of medial subluxation of the patella using iliotibial tract and patellar tendon for repairing the lateral stabiliz-ers of the patella.

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after wide usage, surgeons may question thebasic tenets and may devise clinical research totest the underlying hypothesis, in our case thePFM concept.

In this way we have evaluated retrospectively40 Insall’s proximal realignments (IPR) per-formed on 29 patients with isolated sympto-matic PFM.e The average follow-up after surgerywas 8 years (range 5–13 years). The whole studyis presented in detail in Chapter 2.

One of the objectives of this study was to ana-lyze whether there is a relationship between thepresence of PFM and the presence of anteriorknee pain or patellar instability.

In my experience IPR provides a satisfactorycentralization of the patella into the femoraltrochlea in the short-term follow-up.60 However,this satisfactory centralization of the patella islost in the CT scans performed in the long-termfollow-up in almost 57% of the cases. That is, IPRdoes not provide a permanent correction in allthe cases. Nonetheless, this loss of centralizationdoes not correlate with a worsening of clinical

results. Furthermore, I have not found, in thelong-term follow-up, a relation between theresult, satisfactory versus nonsatisfactory, andthe presence or absence of postoperative PFM.I postulate that PFM could influence the home-ostasis negatively, and that realignment surgerycould allow the restoring of joint homeostasiswhen nonoperative treatment of symptomaticPFM fails. Realignment surgery temporarilywould unload inflamed peripatellar tissues,rather than permanently modify PFM. Moreover,according to Dye, rest and physical therapy aremost important in symptoms resolution thanrealignment itself. Once we have achieved jointhomeostasis, these PFM knees can exist happilywithin the envelope of function without symp-toms. Moreover, in my series, 12 patients pre-sented with unilateral symptoms. In 9 of them thecontralateral asymptomatic knee presented a PFMand only in 3 cases was there a satisfactory cen-tralization of the patella into the femoral trochlea.

We can conclude that not all patellofemoralmalaligned knees show symptoms, which is notsurprising, as there are numerous examples ofasymptomatic anatomic variations. Therefore,PFM is not a sufficient condition for the onsetof symptoms, at least in postoperative patients.Thus, no imaging study should give us an indica-tion for surgery. History and physical exam must


Figure 1.5. Scheme of gadolinium-enhanced MR arthrotomogram of the left knee in the axial plane. Note perfect patellofemoral congruence (a).Note patellofemoral incongruence of the osseous contours (b). (Reprinted from Clin Sports Med, 21, HU Staeubli, C Bosshard, P Porcellini, et al.,Magnetic resonance imaging for articular cartilage: Cartilage-bone mismatch, pp. 417–433, 2002, with permission from Elsevier.)

e We define the term “isolated symptomatic PFM” as ante-rior knee pain or patellar instability, or both, with abnormal-ities of patellar tracking during physical examination verifiedwith CT scans at 0° of knee flexion, but with no associatedintra-articular abnormality demonstrated arthroscopically.

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point toward surgery and imaging only to allowus to confirm clinical impression (see Chapter 6).

Relevance of our FindingsTo think of anterior knee pain or patellar insta-bility as somehow being necessarily tied toPFM is an oversimplification that has posi-tively stultified progress toward better diagno-sis and treatment. The great danger in usingPFM as a diagnosis is that the unsophisticatedor unwary orthopedic surgeon may think thathe or she has a license or “green light” to cor-rect it with misguided surgical procedures thatvery often make the patients’ pain worse (seeChapters 20 and 21).

Tissue Homeostasis TheoryIn the 1990s, Scott F. Dye, of the University ofCalifornia, San Francisco, and his research group,came up with the tissue homeostasis theory.17,19

The initial observation that led to the develop-ment of the tissue homeostasis theory ofpatellofemoral pain was made by Dye, when apatient with complaints of anterior knee painwithout evidence of chondromalacia or malalign-ment underwent a technetium 99m methylenediphosphonate bone scan evaluation of the kneesin an attempt to assess the possible presence ofcovert osseous pathology. The bone scan of thatindividual manifested an intense diffuse patellaruptake in the presence of normal radiographicimages. This finding revealed the presence of acovert osseous metabolic process of the patella ina symptomatic patient with anterior knee painand normal radiographic findings.

The tissue homeostasis theory is in agree-ment with the ideas exposed by John Hilton(1807–1876) in his famous book Rest andPain: 50 “The surgeon will be compelled to admitthat he has no power to repair directly anyinjury . . . it is the prerogative of Nature alone torepair . . . his chief duty consists of ascertainingand removing those impediments with thwartthe effort of Nature.” Moreover, this is in agree-ment with the ideas exposed by ThomasSydenhan (1624–1689), “the father of EnglishMedicine,” and a cardinal figure in orthopedicsin Britain and the world, who looked back toHippocrates, who taught that Nature was thephysician of our diseases. According toSydenhan the doctor’s task was to supplement,not to supplant Nature.50

The tissue homeostasis theory states thatjoints are more than mechanical structures –

they are living, metabolically active systems.This theory attributes pain to a physiopatholog-ical mosaic of causes such as increase of osseousremodeling, increase of intraosseous pressure,or peripatellar synovitis that lead to a decreaseof what he called “Envelope of Function” (or“Envelope of Load Acceptance”).

According to Dye,17 the Envelope of Functiondescribes a range of loading/energy absorptionthat is compatible with tissue homeostasis of anentire joint system, that is, with the mechanismsof healing and maintenance of normal tissues.Obviously, the Envelope of Function for a youngathlete will be greater than that of sedentary eld-erly individual. Within the Envelope of Functionis the region termed Zone of Homeostasis(Figure 1.6A). Loads that exceed the Envelope ofFunction but are insufficient to cause amacrostructural failure are termed the Zone ofSupraphysiological Overload (Figure 1.6A). Ifsufficiently high forces are placed across thepatellofemoral system, macrostructural failurecan occur (Figure 1.6A).

For Dye17 the following four factors deter-mine the Envelope of Function or Zone ofHomeostasis: (1) anatomic factors (morphol-ogy, structural integrity and biomechanicalcharacteristics of tissue); (2) kinematic factors(dynamic control of the joint involving propri-oceptive sensory output, cerebral and cerebellarsequencing of motor units, spinal reflex mecha-nisms, and muscle strength and motor control);(3) physiological factors (the genetically deter-mined mechanisms of molecular and cellularhomeostasis that determine the quality and rateof repair of damaged tissues); and (4) treatmentfactors (type of rehabilitation or surgeryreceived).

According to Dye, the loss of both osseousand soft tissue homeostasis is more important inthe genesis of anterior knee pain than structuralcharacteristics. To him, it matters little whatspecific structural factors may be present (i.e.,chondromalacia patellae, PFM, etc.) as long asthe joint is being loaded within its Envelope ofFunction, and is therefore asymptomatic. Hesuggests that patients with patellofemoral painsyndrome are often symptomatic due to supra-physiological loading of anatomically normalknees components.17 In fact, patients with ante-rior knee pain often lack an easily identifiablestructural abnormality to account for the symp-toms. The Envelope of Function frequentlydiminishes after an episode of injury to the level


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where many activities of daily living previouslywell tolerated (e.g., stair climbing, sitting downin and arising out of chairs, pushing the clutchof a car) become sufficiently high (supraphysio-logical loads for that patient) to lead to subver-sion of tissue healing and continued symptoms(Figure 1.6B). Decreasing loading to within thenewly diminished Envelope of Function allowsnormal tissue healing processes (Figure 1.6C).

Finally, according to Dye many instances ofgiving way, in patients with patellofemoral pain,could represent reflex inhibition of the quadri-ceps, which results from transient impingement

of swollen, innervated peripatellar soft tissues,such as inflamed synovium in patients with nor-mal alignment.

Clinical RelevancePatients with an initial presentation of anteriorknee pain frequently will respond positively toload restriction within their Envelope ofFunction and pain-free rehabilitation program.Moreover, Dye believes that enforced rest afterrealignment surgery could also be important insymptom resolution. Even if patients, parents,and trainers are apt to stubbornly reject any


Figure 1.6. The Dye envelope of function theory. (Reprinted from Operative Techniques in Sports Medicine, 7, SF Dye, HU Staubli, RM Biedert, et al., Mosaic of patho-physiology causing patellofemoral pain: Therapeutic implications, pp. 46–54, 1999, with permission from Elsevier.)

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suggestion to introduce changes into thepatient’s activities and training routine demand-ing an urgent surgical procedure, orthopedicsurgeons should under no circumstances altertheir opinions and recommendations, howeverstrong the pressure exerted upon them may be.Trainers, physical therapists, and physicians allhave a high degree of responsibility and need tobehave in an ethical way.

Patellofemoral Malalignment Theoryversus Tissue Homeostasis TheoryIn essence, the proponents of tissue homeostasistheory look at PFM as representing internal loadshifting within the patellofemoral joint that maylower the threshold (i.e., decrease of theEnvelope of Function) for the initiation and per-sistence of loss of tissue homeostasis leading tothe perception of patellofemoral pain. Painalways denotes loss of tissue homeostasis. Fromthis perspective, there is no inherent conflictbetween both theories. However, these are nottwo co-equal theories. Tissue homeostasis the-ory easily incorporates and properly assesses theclinical importance of possible factors of PFM,whereas the opposite is not true.

In conclusion, I truly believe that both theo-ries are not exclusive, but complementary. Inmy experience, a knee with PFM can exist hap-pily within its envelope of function, but once it isout, for example by overuse, training error, pat-terns of faulty sports movements, or trauma-tism, it can be harder to get back within it, andrealignment surgery could be necessary in veryselected cases.

Myths and Truths aboutPatellofemoral DiseaseMyth: Anterior knee pain and patellar instability arealways self-limited and therefore active treatment isunnecessary. The natural history of this pathologicalentity is always benign.

Traditionally, anterior knee pain syndrome isconsidered to be a self-limited condition with-out long-term sequelae. This is true of manycases but cannot be regarded as a golden rule.A large percentage of patients experience spon-taneous recoveries; indeed, many patientsremain asymptomatic even without specifictreatment. In the case of some of our patients, 10years elapsed from the onset of symptoms untilthe time of surgery; their symptoms not only

failed to improve but they worsened in spite ofthe passage of time and of the patient’s restrict-ing or even abandoning sports practice. Thesesame patients obtained excellent or good resultsafter correction of their symptomatic PFM,which persisted in the long-term follow-up (seeChapter 2). Milgrom and colleagues57 performeda prospective study to determine the naturalhistory of anterior knee pain caused by over-activity. At six years’ follow-up, half of the kneesoriginally with anterior knee pain were stillsymptomatic, but in only 8% of the originallysymptomatic knees was the pain severe, hinder-ing physical activity. Clinical experience showsthat a prolonged and controlled active conserva-tive treatment generally solves the problem. Onthe other hand, trying to negligently ignore theproblem causes disability in some patients.Unfortunately, the patients’ own ambition, aswell as that of their parents and coaches, pre-vails over their doctor’s judgment, which is nec-essarily based on avoiding for at least 3 to 6months any sports movement that could causepain. That is, the fact that this process is onoccasion self-limited should not make us forgetthe need to indicate active treatment in all cases.This means that the process we are studying isreversible at least until a certain point has beenreached. The question we ask ourselves is:Where is the point of no return?

Primary patellar dislocation is not a trivialcondition either. It is true that with the passageof time the frequency of recurrent dislocationstends to diminish, but each episode is a potentialsource for a chondral injury.31 A long-termassessment of patients (mean follow-up of 13years) reveals that conservative treatment ofpatellar dislocation results in 44% of redisloca-tions and 19% of late patellofemoral pain.51

Also, there are studies that establish a connec-tion between PFM and patellofemoral and tibio-femoral osteoarthrosis.28,43 Now, osteoarthrosisis a long-term hazard, both with or without asurgical procedure.31 Davies and Newman13 car-ried out a comparative study to evaluate theincidence of previous adolescent anterior kneepain syndrome in patients who underwentpatellofemoral replacement for isolated patello-femoral osteoarthrosis in comparison with amatched group of patients who underwent uni-compartmental replacement for isolated medialcompartment osteoarthrosis. They found thatthe incidence of adolescent anterior knee painsyndrome and patellar instability was higher


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(p < 0.001) in the patients who underwentpatellofemoral replacement for isolatedpatellofemoral osteoarthrosis (22% and 14%respectively) than in those who underwent uni-compartmental replacement for isolated medialcompartment osteoarthrosis (6% and1% respectively). They conclude that anteriorknee pain syndrome is not always a self-limiting condition given that it may lead topatellofemoral osteoarthrosis. On the otherhand, Arnbjörnsson and colleagues3 found ahigh incidence of patellofemoral degenerativechanges (29%) after nonoperative treatment ofrecurrent dislocation of the patella (average fol-low-up time 14 years with a minimum follow-uptime of 11 years and a maximum follow-up timeof 19 years (range 11–19 years)). Bearing inmind that the mean age of the patients at follow-up was 39 years they conclude that recurrentdislocation of the patella seems to cause patello-femoral osteoarthrosis. In conclusion, PFM’snatural history is not always benign.

Quite often, symptomatic PFM is associatedwith a patellar tendinopathy.2 The latter has alsobeen called a self-limited pathology. It has beenshown that it is not a benign condition that sub-sides with time; that is, it is not a self-limitedprocess in athletes.53 Normally, the injury pro-gresses and when it gets to Blazina’s stage III itgenerally becomes irreversible and leads to thefailure of conservative treatment.53

Myth: Anterior knee pain is related to growth and,therefore, once the patient has fully grown symptomswill disappear.

Anterior knee pain has also been related togrowing pains. It is true that in young athletesduring their maximum growth phase (“growthspurt”) there can be an increase in the tension ofthe extensor mechanism as a consequence ofsome “shortcoming” or “delay” in its develop-ment vis-à-vis bone growth. There may existalso a delay in the development of the VMO withregard to other muscles in the knee and there-fore a transient muscle imbalance may ensue.But it is also true that quite often parents tell usthat the doctor their child saw told them thatwhen the child stopped growing the symptomswould go away and that, nevertheless, these per-sist once the child has fully grown.

Myth: Anterior knee pain in adolescents is an expres-sion of psychological problems.

Many physicians believe that anterior kneepain is a sign of psychological problems.

Consequently this condition has been associatedwith a moderate elevation of hysteria and, to alesser degree, hypochondria with the problem inthe knee being considered an unconscious strat-egy to confront an emotional conflict.44 Likewise,it has been shown that, on some occasions, inadolescent women anterior knee pain with noevident somatic cause can represent a way tocontrol solicitous or complacent parents.44

What cannot be questioned is that anybody atwhatever age can somatize or try to attract otherpeople’s attention through some disease. Inspite of this, one should be very cautious when itcomes to suggesting to parents that their child’sproblem is wholly psychological. Nonetheless, ithas to be recognized that these types of patientspresent with a very particular psychological pro-file (see Chapter 6). Furthermore, there arepatients with objective somatic problems whodisproportionately exaggerate their painbecause of some associate psychological compo-nent or secondary emotional or financial gains.

Unfortunately, in my personal current surgi-cal series (84 patients, 102 knees) there are8 patients (7 females and 1 male) who had beenreferred to a mental health unit. Strangelyenough, these patients’ problem was satisfacto-rily addressed by surgery, which shows that theproblem was not psychological. In addition,both the histological and the immunohisto-chemical and immunochemical techniques–based studies of the lateral patellar retinacula ofthese patients showed objective alterations thatmade it possible for us to detect that the painhad a neuroanatomic base. In short, the ortho-pedic surgeon has the duty to rule out mechani-cal problems as well as other pathologies thatmay cause anterior knee pain before blamingthe pain on emotional problems or feigning.

Myth: Patellofemoral crepitation is in itself an indica-tion of disfunction.

A very common symptom that worries patientsvery much is patellofemoral crepitation.Crepitation is indicative of an articular cartilagelesion in the patella or in the femoral trochlea.Nonetheless, some patients who present withcrepitation have a macroscopically intact cartilageat the moment of performing the arthroscopy.30

The crepitation could be caused by alterations inthe synovial or in other soft tissues.

The International Knee DocumentationCommittee (IKDC)33 stated: “The knee is normalwhen crepitation is absent.” However, thisstatement cannot be upheld after Johnson and


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colleagues45 published their 1998 paper inArthroscopy on the assessment of asymptomaticknees. Indeed, patellofemoral crepitation has agreat incidence in asymptomatic women (94% infemales versus 45% in males).45 Patellofemoralcrepitation has been associated with the lateralsubluxation of the patella, but Johnson and col-leagues45 have observed that lateral subluxationof the patella in asymptomatic persons is morecommon in males than in females (35% vs. 19%).Crepitation is not always present in patients withsignificant pain. Furthermore, when it is presentis does not necessarily cause anterior knee pain.In short, since crepitation is frequent in asympto-matic knees, its presence is more significant whenit is absent from the contralateral knee or whenthere is some kind of asymmetry.

Myth: VMO is responsible for patellar stability.

It has been stated that the vastus medialisobliquus (VMO) is responsible for patellar sta-bility, but we have not found convincing evi-dence in the literature for this belief; and, asligaments are the joint stabilizers, this premisewould appear to be faulty. In theory, the VMOresists lateral patellar motion, either by activecontraction or by passive muscle resistance. Inthis way, in Farahmand’s study,20 lateral patel-lar force-displacement behavior was notaffected by simulated muscle forces at anyflexion angle from 15 to 75°. On the otherhand, the orientation of the VMO variesgreatly during knee flexion. The VMO’s line ofpull most efficiently resists lateral patellarmotion when the knee is in deep flexion, atwhich time trochlear containment of thepatella is independent of soft tissues influ-ences (see Chapter 5).

It seems likely that operations that advancethe VMO include tightening of the underlyingmedial patellofemoral ligament (MPFL), and itwould be responsible for the success of thesurgical technique (see Chapter 2). In thissense, we must note that the VMO tendonbecomes confluent with the MPFL in theregion of patellar attachment. Therefore, itwould be more logical to protect the VMO andaddress the ligament deficiency surgically asneeded (see Chapter 5).

Controversy: Should the Q angle be measured? If so,how should it be measured? Is this of any use?31,58

Another aspect that normally receives greatimportance in the physical examination of these

patients is their Q angle, to the extent thatsome authors regard it as one of the criteria tobe used for indicating a realignment surgery.Nonetheless, values considered to be normalvary greatly across the different studies carriedout. In addition, there are no scientific criteriathat correlate the incidence of patellofemoralpathology with the Q angle measure. Nowadays,some believe that the Q angle, as it is calculated,is not a very accurate way of measuring thepatella’s alignment since the measurement ismade in extension and a laterally subluxatingpatella would lead to a falsely low measurement.In sum, even if Q angle measurement has tradi-tionally been used in the clinical assessment ofpatients with a patellofemoral pathology, cur-rently the usefulness of this measurement isuncertain in spite of the multiple studies per-formed to date. A realignment surgery mustnever be justified on the basis of a high Q angle(see Chapter 20, clinical case 1). The real contro-versy at present is how to measure the Q angle.

Myth: Lateral release is a minor risk-free surgicalprocedure.

Over the years, lateral retinacular release hasbeen recommended for a number of specificpatellofemoral conditions:23 recurrent lateralpatellar dislocations or subluxations, chronic lat-eral subluxation – fixed lateral position, excessivelateral pressure syndrome, lateral retinaculartightness, and retinacular neuromata. A possibleexplanation for this wide range of surgical indica-tions could be that some orthopedic surgeonsconsider the lateral release as a minor risk-freesurgical procedure. However, I believe in agree-ment with Ronald Grelsamer that “There is nosuch thing as minor surgery – only minor sur-geons.” Surprisingly, in a survey of the IPSG23 onisolated lateral retinacular release, published in2004 in Arthroscopy, most respondents (89%)indicated that this surgical procedure is a legiti-mate treatment, but only on rare occasions (1%to 2% of surgeries performed, less than 5 lateralreleases a year). Furthermore, strong consensus(78%) existed that objective evidence shouldshow lateral retinacular tension if a lateral releaseis to be performed.

Although lateral retinacular release is asimple procedure, it can lead to significantcomplications (see Chapters 20 and 21). Inbiomechanical studies, lateral release has beenshown: (1) to reduce lateral tilt of the patella incases in which tight lateral retinaculum is seen


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on CT scans,27 (2) to increase passive medial dis-placement of the patella,64,67 and (3) to increasepassive lateral displacement of the patella.15

Finally, in cadaver knees without preexistinglateral retinacular tightness, lateral release hadno effect on articular pressures when the quadri-ceps were loaded.34

In conclusion, indiscriminate use of lateralrelease is of little benefit and can often causeincreased symptoms. That is the reason whylengthening of the lateral retinaculum is thetherapy chosen by authors such as RolandBiedert (see Chapter 20).

Reality: Patellofemoral pathology leads to diagnosticerror and, therefore, to inappropriate treatments andto patients being subjected to multiple proceduresand to a great deal of frustration.

All myths and controversies analyzed through-out the present chapter could lead the reader toattribute importance to things that in actual factare unimportant (i.e., crepitation) or, on thecontrary, to underrate or cast aside complaintslike anterior knee pain or functional patellarinstability, considering them to be either a psy-chological problem or a condition bound to sub-side with time. Sometimes we do not go farenough, which may lead us to overlook otherpathologies (diagnostic errors leading to thera-peutic errors). In other cases we overdo it andtreat cases of malalignment that are not sympto-matic. So we have seen patients with symptomsof instability who were treated for malalignmentwhen what they really had was instability causedby a tear in their ACL.

We have also seen patients treated for ameniscal injury who really had isolated sympto-matic PFM. In this connection it is important topoint out that McMurray’s test, traditionallyassociated with meniscal pathology, can lead toa medial-lateral displacement of the patella andalso cause pain in patients with PFM. Finally, itis worrying to see how many patients arereferred to outpatient orthopedic surgery prac-tices in our hospitals with an MRI-based diag-nosis of a tear in the posterior horn of themedial meniscus who during clinical examina-tion present with anterior knee pain and nomeniscal symptoms. It is a proven fact thatgiven the overcrowding of outpatient units’orthopedic services and because of social pres-sure, as time passes doctors tend to conductmore superficial physical examinations and toorder more MRIs. In this way we must remem-

ber the statement by Dr. Casscells:10 “Technology:a good servant, but a bad master.” According toAugusto Sarmiento, former Chairman of theAmerican Academy of Orthopedic Surgeons(AAOS), MRIs are unfortunately replacing thephysical examination when it comes to assessinga painful joint.62 MRI is not a panacea and,what’s more, it gives rise to false positives.Patients’ great faith in technology and theirskepticism regarding their doctors and anincreasingly dehumanized medical practice hasresulted in the failure of partial arthroscopicmeniscectomies owing to a bad indication, infrustrated patients, and in the squandering ofresources. In 1940, Karlson46 wrote the followingabout chondromalacia patellae: “The diagnosisis difficult to make and the differential diagnosisof injury to the meniscus . . . causes special diffi-culties, as in both these ailments [meniscal andpatellar pathology] there is a pressure tendernessover the medial joint space.” Hughston endorsedthese words when he stated, first in 1960 and thenin 1984:36 “The orthopedic surgeon who has notmistaken a recurrent subluxation of the patellafor a torn meniscus has undoubtedly had a verylimited and fortunate experience with knees andmeniscectomies.” Just think of the sheer amountof arthroscopies performed unnecessarily on thebasis of a complaint of anterior knee pain!

Nowadays this problem has been magnifiedbecause of the relative ease with which meniscec-tomies are indicated and performed thanks tothe benefits of arthroscopy. In a lecture deliveredat the Conference of the Nordic OrthopaedicFederation held in Finland in 2000, AugustoSarmiento stated that the number of unnecessarysurgeries (including arthroscopies) carried outin our field in the United States is extremelyhigh.62 It is therefore essential to underscore theimportance of physically examining the patient(see Chapter 6).

Finally, another source of frustration for thepatient is the lack of communication with his orher doctor (dehumanized medicine), which maylead to unrealistic expectations. It is essential forthe patient to understand the difficulties inher-ent in treating patellofemoral problems. This isthe only way in which patients can be satisfiedafter surgery even if their symptoms do not dis-appear completely.

Reality: “Treatment should be customized.”

It is very important to identify the pathologicalalteration responsible for the clinical aspect of


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this clinical entity to select the most effectivetreatment options based on clinical findings(made-to-measure treatment). This will yieldthe most satisfactory results. At present, mini-mal intervention (e.g., specific soft tissue exci-sion of painful tissue47) and nonsurgicalmethods are emphasized (see Chapters 9 and10). Obviously, if the etiology of patellofemoralpain and patellar instability is multifactorial,then the evaluation must be multifactorial, andthe treatment should be multifactorial also.56

This should lead to a simplified treatment plan.We must find out what is wrong and fix it; thatis, we must address specific identifiable pathol-ogy (e.g., peripatellar synovitis, serious rota-tional alterations, etc.). In the few patients whorequire surgery, a minimalist surgical approachis the best in most cases.19,47 We agree with thestatement of Philip Wiles in 1952: “Howeverimportant surgery may be now, it should be theaim of all doctors, including surgeons, to limitand ultimately abolish it.” 50

ConclusionsThe pathology we discuss in the present mono-graph presents itself with a multifactorial etiol-ogy and a great pathogenic, diagnostic, andtherapeutic complexity.

The consideration of anterior knee pain to bea self-limited condition in patients with anunderlying neurotic personality should be ban-ished from the orthopedic literature.

Our knowledge about anterior knee pain hasevolved throughout the twentieth century. Whileuntil the end of the 1960s this pain was attributedto chrondromalacia patellae, a concept born atthe beginning of the century, after that period itcame to be connected with abnormal patello-femoral alignment. More recently, the pain wasput down to a wide range of physiopathologicalprocesses such as peripatellar synovitis, the incre-ment in intraosseous pressure, and increasedbone remodeling. We are now at a turning point.New information is produced at breakneckspeed. Nowadays, medicine in its entirety isbeing reassessed at the subcellular level, and thisis precisely the line of thought we are followingin the approach to anterior knee pain syndrome.Still to be seen are the implications that thischange of mentality will have in the treatment ofanterior knee pain syndrome in the future, but Iam sure that these new currents of thought willopen for us the doors to new and exciting per-

spectives that could potentially revolutionize themanagement of this troublesome pathologicalcondition in the new millennium we have justentered. Clearly, we are only at the beginning ofthe road that will lead to understanding whereanterior knee pain comes from.

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Background: Patellofemoral Malalignment versus Tissue Homeostasis

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