Musculoskeletal Diseases and Disorders: Knee and Patella PTP 521.

Musculoskeletal Diseases and Disorders: Knee and Patella

PTP 521

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Fractures

• Knee Ottawa Rules• A knee x-ray is only required for knee injury patients

with any of these findings:– age 55 or over – isolated tenderness of the patella (no bone tenderness of

the knee other than the patella) – tenderness at the head of the fibula – inability to flex to 90 degrees – inability to weight bear both immediately and in the

casualty department (4 steps - unable to transfer weight twice onto each lower limb regardless of limping).

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FRACTURES OF THE KNEE AND PATELLA

Fractures of the Distal FemurClassified by location

Supracondylar: occur superior to the femoral condyles.

Common patterns are comminuted, impaction, linear, with or without displacement

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Intercondylar:

Occurs between the medial and lateral femoral condyles.

Fracture pattern is commonly called a "Y" fracture.

Condyles split apart from each other and from the shaft of the femur.

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Condylar

Usually linear and involves only one femoral condyle

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Fractures of the Proximal Tibia

Most frequent occurrence is at the medial and Lateral tibial plateaus with the lateral plateau most often involved.-difficult to see and treat.

Mechanism of injury is a varus or valgus force

combined with axial compression. Generally considered to be impaction fractures.

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Because of the difficulty in viewing the tibial plateau, conventional tomography is

needed in addition to the routine x-rays.

• A classification system has been developed to identify the 6 most common fracture patterns.

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Tibial Plateau Fractures

• Two systems: book has the Hohl system highlighted very well.

• Second system is the scharzker method. http://uwmsk.org/schatzker/

• The web site above has a great representation of the Scharzker classification with a unique way of viewing the CT scans. The cursor can move over the radiograph and the picture below shows the corresponding CT view.

• These two systems are not very different.

http://uwmsk.org/schatzker/

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Comparison

Hohl Classification Schatzker Classification

• Type I• Type II• Type III• Type IV• Type V• Type VI

• Same as Hohl Type I• Type III • Type II• Same as Hohl Type IV• Same as Hohl Type V• Same as Hohl Type VI

Main difference between the two classifications is the placement of Type II and Type III which are switched in the two classification types. Be sure you see which classification is being used when dealing with a tibial plateau fracture to understand the bone dysfunction.

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Hohl System

• Hohl Type I: nondisplaced vertical split fracture of the lateral tibial plateau caused by a pure valgus force

• Schatzker Type I: Pure split on lateral side

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• Hohl Type II: a local depression of the lateral tibial plateau caused by a combination of axial and valgus forces

• Schatzker Type III: Pure central depression - Lateral condyle

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• Hohl Type III: a displaced vertical split fracture with depression at the lateral plateau, caused by a combination of valgus and axial forces and often associated with a proximal fibula fracture.

• Schatzker Type II: Split with lateral depression

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• Hohl Type IV: a displaced depressed fracture of the medial plateau, caused by varus and axial forces

• Schatzker Type IV: fractures of medial condyle

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• Type V: a vertical split fracture of the anterior or posterior aspect of the tibial plateau, caused by axial forces

• Schatzker Type V: Bicondylar fractures Continuity of metaphysis & diaphysis maintained

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• Hohl Type VI: a displaced, comminuted fracture of both condyles, caused by axial forces, often associated with proximal fibula fractures

• Schatzker Type VI: Dissociation of metaphysis & diaphysis in addition to plateau

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Fractures of the Patella

MOI: direct trauma from falls or blows or indirect trauma from tension forces.

-change in force, action of muscle.

Direct trauma: – Patella fractures as it compresses against the femur. – Most frequent pattern is a transverse linear fracture line through

the mid-region of the bone. – Vertically oriented fractures and comminution are also seen.

Avulsion fractures of the patella occur as a result of indirect trauma

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Patellar Fracture Patterns

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Patella Fractures

• Patella fractures– Lateral view– AP view– Sunrise view

– Patella Alta– Avulsion fracture of

patella ligament

http://emedicine.medscape.com/article/394270-overview

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AP and Lateral Views of the Displaced Transverse Fracture of the Patella


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Sunrise view: MRI On the left is a patella dislocation, high signal intensity on the lateral side

View on the right is a bipartite patella. Can be confused with a fractured patella


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• Full thickness fissure of the patella articular cartilage

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• Joint effusion• Transverse View, fast

spin echo T2-weighted fat saturated MR

• Normal cartilage with joint effusion surrounding it

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Joint Dysfunctions of the Knee

Rheumatoid Arthritis: discussed under wrist and hand

Rheumatoid arthritis. Anteroposterior knee radiograph shows diffuse uniform joint space narrowing.

Bone on Bone, uniform narrowing.

Jacobson J A et al. Radiology 2008;248:737-747

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Osteochondritis Dessicans

Definition: avascular necrosis of the condylar epiphysis of the femur

Medial femoral condyle involved in 75% of the cases, lateral condyle can also be affected, results in a osteochondral fracture

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Etiology: traumatic – Caused by impingement of the tibial spine on

the femoral condyle – Or a loss of circulation to the osseous tissue of

the epiphyseal plate– Or an avulsion of the proximal attachment of the

PCL

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• SX: – aching pain in the knee at rest – worse with weight bearing activities– insidious onset – episodes of knee joint locking

• Signs: – antalgic gait pattern – knee joint effusion – restriction in range of motion present

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• Radiographs: – AP, lateral, and tunnel will show a lesion that

appears like a half moon defect on the subchondral bone

• RX: – Decrease or elimination of WB with

immobilization

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Osteonecrosis:

• Avascular necrosis of the knee occurring in adults,

• Typically women age 50 years or more.

• Medial compartment of the knee and femoral condyle more involved than tibial condyle.

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Osteoarthritis.

Jacobson J A et al. Radiology 2008;248:737-747

©2008 by Radiological Society of North America

Osteoarthritis: joint space narrowing, sclerosis, and osteophyte formation (arrow) predominately involving the medial compartment.

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DJD/OA of the knee

• Standing AP view of the knee’s – Weight Bearing

Important.

• Typical finding is sharpening of the tibial spines

• Narrowing of the medial compartment

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• This view shows osteophyte formation on the tibial plateau, medial side

• Narrowing of both the medial and lateral compartments, but more on the medial.

• More advanced OA

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• Patello Femoral OA seen in a lateral view

• Patellofemoral compartment narrowing

• Osteophyte formation on both the superior and inferior aspect of the patella

• Try bending this knee– Patella will have more pain

in flexion (stairs) , but relief in extension

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Surgeries: High Tibial Ostotomy

Occurs in patients with unicompartmental osteoarthritis.

• Usually the medial compartment with a varus deformity noted.– New but effective.

Patients age is usually under 65 years of age, generally exclude patients with RA or other systemic diseases

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Indications for Tibial Osteotomy

• Best results occur in patients under 50 years of age

• Body mass index greater than 25 kg per square meter?

• Isolated medial compartment OA, • No lateral thrust at the knee, • A varus deformity less than 10 dg • Range of motion greater than 0 - 120 dg

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Contradictions

• Inflammatory arthritis: RA, Sceriatic Arthritis• Significant ligamentous instability • Age greater than 70years • Severe patellofemoral arthritis • Flexion contracture greater than 15 dg

– Won’t get good contact, so bone won’t heal properly.

• Varus deformity greater than 15 dg

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Technique: wedge resection

http://www.ortho-u.net/image7/hto1.jpg

http://www.ortho-u.net/image3/i1/hto1.jpg

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Goal of Surgery:

• Realign the weight bearing axis so that the pressure on the tibial plateau is shifted laterally into the area of the intercondylar eminence and the tibial spines rather than the medial condyle

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Unicompartmental replacement

• Replace only one part of the knee but maintain the natural joint/bony surfaces on the other part. – Used when ACL surgery fails

• Generally will replace the medial compartment.

• To function successfully, the anterior cruciate ligament needs to remain intact

http://www.ortho-u.net/image9/i1/uni1.jpg

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Total Knee Replacement

Indications: a. Chronically disabling degenerative knee pain b. Failed conservative measures

Contradictions: a. Acute infection elsewhere in body b. Charcot arthropathy or absence of sensation in the

joint c. Infection within the joint d. Severe spasticity associated with contractures.

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Relative contra indications a. Severely demented or bedridden

patients (unless needed for transfers) b. Osteoporosis (depends on bone density of

femur and tibia) c. Significant peripheral vascular disease (if it

won’t heal)

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Prosthetic Devices

Classified as constrained, semi-constrained, or minimally constrained

constrained: actually hinges, knee doesn't function as a

simple hinge though and these prostheses have a high failure rate, reserved for the patients with severe instability problems or severe deformities

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Semi-constrained

• Posterior cruciate ligament is absent or taken out as a result of the surgery.

• This is designed to prevent subluxation or dislocation of the tibiofemoral joint resulting from the absence of the ligaments.

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Advantages and Disadvantages of the Preserving the PCL

• Advantages– restores more normal knee kinematics – more normal stair climbing abilities

• Disadvantages – excessive rollback of femur on tibia if PCL is too tight – difficult to reproduce the preoperative joint line – ligament length more difficult to balance with the

collateral ligaments – more difficult to correct large flexion contractures

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Minimal constrained:

• Reproduces the anatomical contours of the knee

• Relies heavily on soft tissue to provide joint stability

– Usually done with younger individuals, so can freely do activities.

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Surgical Preparation

http://www.ortho-u.net/image3/tkkr1.jpg

http://www.ortho-u.net/image4/i1/tkr11.jpg

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TKR Rehab: “joint camp”Goal of a TKR is to provide patient with a stable, pain-

free knee joint with a functional range of motion-Usually there for 4 days or less.

Postoperative Problems: knee stiffness which can lead to adhesions=work on flexion.

Functional considerations: need at least 90 dg of flexion to be able to do most ADL's and greater than 90 dg's is needed to go from a sitting to a standing position.

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Patellofemoral Dysfunctions:

Patella Instabilities

Patella Dislocation: associated with an excessive lateral pull of the vastus lateralis and IT band

MOI: acute trauma or twisting force with a

combination of flexing femur, externally rotating femur while foot is planted

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Subluxation of the Patella: same mechanisms as a dislocation

• Patella should mirror the condylar divot. Shifted slightly like seen is a subluxation. Over more would be a dislocation.

http://www.ortho-u.net/image3/i1/hto1.jpg

http://www.ortho-u.net/images/i1/padis1.jpg

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Factors which predispose a patient to subluxation or dislocation:

1) Q angle greater than 20 dg2) Excessive external rotation of tibia (in prone) 3) Increased internal rotation of the femur (stand behind and look

at medial hamstrings coming at you that’s IR of femur) 4) Patella alta –(high patella) considered most important, tape

measure=if length of patella is shorter than distance from the posterior apex to tibia tuberosity.

5) Shallow trochlear groove 6) Small flat patella7) Atrophy of vastus medialis (hold patella, then do a quad set, see

where it is pulled, usually lateral) 8) Muscle imbalance/weakness relative to

the vastus lateralis

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SX and Signs

SX: – onset occurs with sudden activity valgus – external rotation force

Signs: – Hemarthrosis -bleeding into joint.– tenderness to palpate – apprehension to lateral patella joint movement

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Chondromalacia Patella

• Patellofemoral tracking dysfunctions: new term (to make it seem less chronic)

Progressive softening, fibrillation and finally degeneration of the articular cartilage on the underside of the patella-Seen with younger girls (13-15)

Overuse syndrome with altered patellar biomechanics occurring.

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Chondromalacia=

SX: retropatellar pain described as aching with sitting.

Signs: + movie goers sign

(forced into full knee flexion for a long period of time), + full knee flexion test (takes 30 to 60 seconds for achy pain to start)

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Stages: I - IV

I: swelling and softening of the cartilage

II: fissuring w/in the softened areas

III: fasciclations of articular cartilage almost to level of subchondral bone

IV: destruction of cartilage w/ subchondral bone exposed– Histologically Stage IV is virtually indistinguishable from DJD

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Larsen-Johansson's Disease

Necrosis of the patella poles– occurs in children 8-13

years of age

etiology unkown, insidious onset

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SX and Signs

SX: – pain with resisted extension of the knee, – pain with kneeling, – pain with activity

Signs: – swelling and tenderness to palpation over the inferior pole

of the patella

X-ray: may or may not show fragmentation of the bone near the affected pole

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Musculotendinous Dysfunctions of the Knee

Osgood Schlatter's Disease: Tibial Apophysisitis

-inflammation of the tibial tuberosity, which goes bone growth.

Develops when the epiphysis

undergoes the transition from cartilage to bone.

Develops in the patella tendon/bone insertion-more cosmetic, then chronic pain.

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Osgood Schlatters Disease

• Traction on the patella ligament results in microfractures.

• The body tries to heal itself and an outgrowth of the tibial tuberosity occurs.

• Occurs in males more than females, ages 12-14– During a growth period

Differential Diagnosis: Mechanical dysfunction, mimics patellar tendonitis or patellofemoral pain syndrome

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SX and Signs

Sx: – pain in the region of the tibial tubercle– related to activity particularly sports – pain relieved by rest – hurts to kneel

Signs: – swelling over the tibial tubercle– tenderness to palpation over the tibial tubercle

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Radiographs: lateral view may show irregular ossification or fragmentation of the tibial tubercle

RX: • Rest, may try bracing to give patella tendon some assist • Avoid resisted knee extension activities until the pain has

gone away. • Time is usually 6-8 weeks, may cast• Surgery – rare

• *Issue how to keep kid from running and jumping when pain in minimum.

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TendonitisPatella tendonitis or jumper's knee:SX:

– pain during activity, – pain after activity, – pain with sitting for a long period of time– tenderness noted at inferior pole of patella

Signs: – tenderness to palpation, – pain with resisted knee extension– swelling over the patella tendon region– pain with passive stretch

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Quadriceps Tendonitis• Superior pole of the patella at the tendon junction. Occurs in

sports that require a lot of running and jumping or acceleration - deceleration activities like soccer or basketball

SX: – pain during activity– pain after activity

Signs: – tenderness to palpate over the superior pole of the patella– pain with resisted knee extension– pain with passive stretch of the quadriceps

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Iliotibial Tract TendonitisFriction between the underlying structures and the iliotibial

tract, occurs in runners or patients whose occupation or hobbies lead to a tight iliotibial tract.

SX: – pain with activity– pain over the lateral thigh closer to the knee

Signs: – + Ober's test– pain with resisted abduction– tenderness to palpate over the lateral epicondyle

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Popliteus tendonitis

Develops with excessive downhill running, excessive squatting activities-X-cross country, squatting.

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Inert Tissue Dysfunctions of the Knee

LigamentMedial Collateral Ligament• a. MOI: valgus force applied

to the lateralaspect of the knee with the foot fixed, knee

in extension

• b. Less common MOI: knee in slight flexion (less than 90 dg), or twisting motion occurs

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Symptoms and SignsSX:

– mild tenderness at medial joint line– swelling

Signs: – Grade I, II, or III laxity with valgus stress,– AROM is painful near the end of extension– edema present– point tender at adductor tubercle and/or medial joint line

– ALWAYS check it in the position that it was injured in, also before inflammation or after it goes down.

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Stress Test Analysis

• Mild medial laxity with valgus stress, • Knee in full extension: damage to posterior oblique

ligament and capsular ligament• Gross instability at full extension: check ACL and PCL

to make sure they are tight• Empty end feel or indistinct end feel: secondary

restraints are holding the knee, ligament is grade III

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Medial Collateral Ligament

• Ligaments turn up as BLACK

• Coronal Images used to evaluate MCL tears

• Proton density coronal image – arrows

• Show ligament as thin, well defined, low signal intensity from medial femoral condyle to the medial tibial metaphysis


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Lateral Collateral Ligament

MOI: Varus force from the medial side of the knee.

– Isolated injuries are rare because of ligament's location posterior to the axis of the knee joint.

– Not as commonly injured, as very stable.

– Usually injured as a torsional overload that also affects the cruciate ligaments

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Sx and Signs

SX: lateral knee pain

Signs: – varus laxity in extension

and flexion– numbness or tingling if

nerve root is involved: common peroneal

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• Oblique orientation, low signal structure – white arrow

• Inserts onto fibular head

• Avulsion fracture of the fibular head may be seen on plain film radiographs with a

LCL injury http://emedicine.medscape.com/article/401472-overview

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• LCL and MCL tear


LCL is outside the capsule,A tear in the LCL does not Cause as much effusion as A MCL tear. You will not seeAn increased signal intensityAround the ligament as youdo in an MCL tear.See figure to the right.

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Anterior Cruciate Ligament:

MOI: combination of valgus and external rotation forces applied to the knee while foot is in a closed pack position

Less common MOI: excessive internal rotation and hyperextension combination– non contact injury in which sudden limb

deceleration is accompanied by a contraction of the quads producing damaging force moments

– Commonly the MOI for woman.

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ACL Tear

• Arrow’s point to the tear

• Less formation of the tendon

www.health-pic.com/.../

http://www.health-pic.com/for-anterior-cruciate-ligament-injury/

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• Non visualization of an ACL


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• Triad of images showing an ACL tear

• Top left: T2 Sagittal view• Top right: T2 coronal

view• Bottom: T1 coronal

view,


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Anterior Cruciate Ligament

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SX and SignsSX: • Patient reports a "pop" at time of injury • Knee swelling within one hour after injury• Hemarthrosis within 12 hours

Signs: • + Lachman's• + pivot shift test• + anterior drawer test• Hamstring muscle spasm: can give a false negative as they protect

any movement from anterior drawer. • Inability to fully weight bear on affected side• Weakness and knee giving way are frequent occurrences

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Chronic problem• Frequent episodes of knee giving out. Pain and effusion with

specific activities that stress knee such as cutting and pivoting

RX: depends on the degree of tear, Will generally wait 2-3 weeks until the swelling has decreased before going in and assessing the ligament

• MRI is diagnostic as is arthroscopic surgery

Surgery: Type of graft used will depend upon the physician. Great controversy in the literature regarding the graft type.

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Patella - Tendon Graft:

• Central third of the patella tendon is taken to use as a graft, so quads will be affected.

• Considered to be 57% as strong as original ACL at 3 months and 87% as strong at 12 months.– At first will decrease in strength, but eventually will remodel

and become stronger.

• Some take the tendon from the opposite side, as will have balance out, but now will have issues on both side.

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• Two type of Patella Tendon grafts: – Injured leg.

• Have to deal with two injuries then, a decrease in the quad mechanism and the ACL repair

– Second is taken from the uninvolved leg. • Gives a strong patella tendon on the ACL side but a

weaker tendon on the opposite side (Shelbourne Procedure)

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Semitendinosus and Gracilis Grafts

• Provide weaker initial fixation and have a more prolonged and variable rate of fixation into the bone than does the central third patella grafts.

• Used when there is a significant incidence of patellofemoral and anterior knee pain associated with the injury– Weakening the hamstring.

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• These tendons can be removed, doubled over, and then used to replace the ACL.

• These tendons are easier to harvest than the patellar tendon, they require smaller drill holes in the femur and the tibia for fixation, and they do not predispose patients to patellar tendinitis.

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Types of Grafts

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ACL Patella Tendon Graft Surgery

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Allografts: Cadaver graftsIndications:• Failed autograft surgery• Significant patellofemoral arthrosis• Narrow patella tendon• Patients who don't want to use their own tissue3 areas of concern: 1. Immune reaction 2. Potential disease transmission 3. Remodeling and effect on mechanical

properties

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Posterior Cruciate Ligament

MOI: anteromedial blow to the flexed knee or a fall onto the knee with foot and ankle plantarflexed

Common component is the posteriorly directed force on the proximal tibia which pushes the tibial plateau posterior on the femoral condyles

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PCL:

• All three images should be

used, sagittal, coronal and axial

• T1 Coronal Image

• Darker arrow is the PCL and is

a lower intensity signal than the

ACL

• Lighter arrow is the ACL


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Sagittal View

• Proton dense sagittal image

• Insertion site (arrows) is posterior to the tibia articulating surface


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• Avulsion fracture of the PCL as demonstrate on an AP radiograph


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• Interstitial tear of the PCL

• A: proton density sagittal image

• B: T2-weighted sagittal image


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• Mid substance tear of the PCL- large arrow

• Proton dense-weighted sagittal view

• Intact PCL proximally, tear, edema noted mid PCL

• Ligament of Humphrey – small arrow


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SX and Signs:

Sx: – Difficulty weight

bearing – Painful – Instability with

stairs and inclines

– Recurrent swelling

Signs: – ROM is usually WNL – Painful on end

range flexion – Extensor lag

present (tibia drops below the femur)

– + posterior drawer test

– + tibial sag test– + hughston test

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Surgery

Surgery is controversial if only PCL is ruptured,

Grade I PCL injuries with less than 5 mm of increased posterior translation of the tibia are managed non-operatively.

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Surgical Reconstruction

Surgical reconstruction is recommended for isolated PCL disruption that result in 10 mm if increased posterior tibial translation.

Also used with PCL injuries combined with injury to other ligamentous structures

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Inert Structure Dysfunctions

Meniscus:Medial meniscus is more frequently injured than the lateral

meniscus.(similar to SLAP lesions of the GH)

Location of the tear will dictate the response to injury a. periphery: good repair, vascular, get

a fibrocartilage scar tissue b. central portion, avascular, poor repair

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Tears: MOI: traumatic,

– occurs in the 13 to 40 year olds, – occurs with activity that may or may not be contact related – non-contact: acceleration or deceleration stresses

combined with a sudden change in direction, squatting or twisting

– produces a longitudinal or transverse vertical tear

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Types of Tears

Stoller, D. Pocket Radiologistwww.health.allrefer.com

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Types of Tears

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Vertical Longitudinal Tears

• Most frequent, • Medial 2.5:1 greater incidence than lateral meniscus• peripheral tear • Greater than 1 cm in length • Unstable with stress • Causes symptoms • Treat with surgery

– short, less than 5mm, full thickness to partial thickness – stable, rarely cause symptoms, no surgery

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Meniscal Tears: Longitudinal Tears

• Axial illustration of a full-thickness longitudinal tear of the posterior horn.

• The meniscus is viewed from above in (a), sagittal in (b), and coronal in (c).

• A = anterior, L = lateral, M = medial, and P = posterior. http://emedicine.medscape.com/articl

e/399552-overview



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Longitudinal Tear of the Meniscus

• Coronal T2 image (with fat suppression) shows a displaced fragment (arrow) of medial meniscus into the intercondylar notch of the knee.

• Also known as a bucket handle tear

http://www.radrounds.com/main/sharing/share?id=1791588%253APhoto%253A28117

http://www.radrounds.com/main/sharing/

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Vertical Transverse tears

• Radial tears, less common, almost always the middle third of the lateral meniscus

• Stable less than 5 mm

• Surgery if it causes symptoms

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Radial Tear

• Axial illustration of a full-thickness radial tear of the posterior horn.

• The meniscus is viewed from above.




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Degenerative tears• Horizontal cleavage or flap tear.

• Increase incidence in age over 40,

• No specific injury or minor degree of stress can cause the tear.

• Can occur in either meniscus, associated with degeneration of the articular cartilage

• After age 40, will often have a horizontal splitting as a result of bending, squatting, turning and twisting over the years.

• Horizontal lesion seen in people over age of 55, not always symptomatic.

• More common in the medial meniscus, usually occurs at the junction of the middle and posterior one-third

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Horizontal Tear of Posterior Horn

• Axial illustration of a full-thickness horizontal tear of the posterior horn. The meniscus is viewed from above.

• Not the same as the radial tear, goes through the substance of the meniscus in a horizontal, not vertical line http://emedicine.medscape.com/articl

e/399552-overview



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Posterior Horn Tear: Horizontal

• Fat-suppressed proton density-weighted sagittal images reveal a horizontal tear of the posterior horn of the medial meniscus (arrows), extending to the tibial surface.

www.radsource.us/clinic/0802

http://www.radsource.us/clinic/0802

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Flap tear

• Axial illustration of an oblique (parrot beak) tear of the posterior horn.

• The meniscus is viewed from above.

• In B, image 1 is most lateral, image 2 is middle, and image 3 is most medial.

• In C, image 1 is most anterior, image 2 is middle, and image 3 is most posterior.



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Parrot Beak: Oblique Tear



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SX and Signs

SX: • Pain at time of

injury • Persists and

interferes with WB activity

• Recurrent episodes with minor stress

• Baker's cyst• Knee is giving way

Signs: • Change in WB status• Minimal swelling

may be noted with girth measurements

• McMurray's or Apley's test are positive

• Springy end feel

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RX: surgery

• Link between an absent meniscus and OA. • Indications for surgery:

– Vertical tears– Tears near the periphery of the meniscal

substance– Generally intact meniscal body– Total tissue defect less than 2 cm

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Synovial Plica

Remnant of 3 embryonic pouches of synovial membrane which remain in the knee as excessive synovial material.

Medial plica is the most symptomatic .

Will tighten during knee flexion and cause a change in the normal mechanics of the patellofemoral joint.

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• Example: like a fine lace curtain

• Probably causes no symptoms,

• Although the elastic edge may bow-string over the bone of the femur when the leg bends and straightens

• Should there be an injury affecting the plica, however, the edge can thicken and then cause regular symptoms of a 'catching' pain at particular joint positions.

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Examples of Synovial Plica

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SX and Signs:

Sx: Similar to patellofemoral pain syndromes. – Pain in the medial aspect of the knee joint– Clicking – Intermittent locking sensation on medial side – Generalized weakness – Reports of joint instability – Classic symptom is an inability to sit for prolonged periods

of timeSigns: must rule out meniscus and ligamentous

injuries, bone injuries, radiographs, MRI, CT scans

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RX

• Conservative treatment with NSAIDS • Modalities • Exercise • May use transverse friction massage

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Bursitis

Prepatellar Bursitis: injury through direct trauma or chronic irritation such as prolonged kneeling.

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SX and Signs

SX: – Localized pain and swelling in the bursa– Tenderness to palpation

Signs: – Swelling of the bursa – Warm to touch – Redness – Slight loss of knee flexion – Strong but painful resisted knee extension

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RX:

• Pain and edema control• Anti-inflammatories• Modalities in treatment• May inject corticosteroids or drain bursa

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Bakers Cyst:Definition: any form of synovial herniation or bursitis involving

the posterior aspect of the knee. Often occurs in conjunction with an intra-articular derangement at the knee such as a meniscal tear or ACL injury

a. SX: mass behind the knee that may or may not be tender

b. Signs: well defined, edematous mass on the posterior aspect of the knee

c. When present, must rule out an internal derangement.

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Images of Baker’s Cyst

www3.americanradiology.comwww.med.umich.edu

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Pes Anserine Bursitis

Definition: follows a traumatic injury or unaccustomed WB exercise

SX: Medial knee pain– Aching at rest– Swelling may be present on medial aspect

of kneeSigns:

– Tenderness to palpation– Pain with resisted flexion

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Common Imaging

• Anteroposterior View• Lateral View• Sunrise View of the

Patella• Tunnel View of the Knee

• MRI – Meniscus Imaging– ACL Imaging– PCL Imaging

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RADIOGRAPHIC EXAMINATION OF THE KNEE AND PATELLA

Anteroposterior view: Important to do weight bearing if possible.

Either way, you should note if the x-rays were taken in

standing or while lying supine.

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Alignment:Identify the following structures

• distal femur • medial and lateral

condyles • the proximal tibia• fibula • the patella

superimposed over the distal femur

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Look at joint space for the tibia and femur, well defined in both medial and lateral views

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• Normal knee: slight valgus alignment

• Medial and lateral joint spaces should be equal

• Femoral condyles should be aligned with the tibial plateaus

• Increase in valgus or a varus mal-alignment will increase stress on medial or lateral compartment, resulting in sclerosing of the femoral condyle and tibial plateau

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Anteroposterior view:

One of these is WB and one is N WB – how can you tell?

Look at the medial joint line on right leg especially

1

2

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AP: Bone Density

• Abnormal bone density: may see Osteochondral defects (OCD) on medial or lateral condyles of the femur

• Blue arrow points to a radioluscent cresent area on the knee: osteochondral dissecans

www.learningradiology.com/archives06/COW%2022...

http://www.learningradiology.com/archives06/COW%20220-Osteochondritis%20dissecans/osteochondritisccorrect.html

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Cartilage

• Clear, wide joint space

• Abnormal for there to be diminished space

• Generally, one condyle is involved first, then both in advanced stages of OA

• Bone on bone – absence of meniscus

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Lateral View:

Views the patellofemoral joint in profile, knee is flexed anywhere's from 20 dg to 45 dg and the beam is directed from a medial to lateral direction.

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Look for the relationship of the patella to the femur, can determine patella alta or patella baja

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Insall-Salvati Index: PLR = PL/TL

The length of the patella ligament is measured from its attachment at the patellar apex to the tibial tuberosity (TL) and should equal the length of the patella (PL) from the superior to the inferior poles.

Variance greater than 20% indicates an abnormal patella position.

www.medscape.com/viewarticle/553776_2

http://www.medscape.com/viewarticle/553776_2

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Lateral: Bone Density

• Increase in density as the condyles are superimposed on each other

• Medial condyle is larger and extends distally further than the lateral condyle

• Patella should be consistent in density

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Sunrise View or Skyline View Patella appears to be the sun, rising

over the horizon

Axial view of the Patellofemoral joint: Gives the articular surfaces of the patella and femur.

Medial and lateral facets of the patella are visible

Alignment of the patella in relation to the femur – lateral, medial etc.

www.hawaii.edu/.../pediatrics/pemxray/v6c08.html

http://www.hawaii.edu/medicine/pediatrics/pemxray/v6c08.html

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Note the sulcus angle of the femur:

• normal value of 138 degrees +/- 6 degrees

• shallow sulcus angles (greater degree within the angle) have been associated with recurrent patellar dislocations.

www.medscape.com/viewarticle/553776_2

http://www.medscape.com/viewarticle/553776_2

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• Note the congruence angle which helps to define the position of the patella within the inercondylar sulcus.

• Normal value is -6 degrees.

• Congruence value of +16 has been associated with lateral patellar subluxation

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• To measure the congruence angle: Find the highest point of the medial (B)and lateral (C) condyle and the lowest point of the intercondylar sulcus (A)

• The angle BAC, is the sulcus angle. Bisect the sulcus angle to establish the zero reference line, AO.

• Find the lowest point on the articular edge of the patella (D)• Project line AD. • The angle DAO is the congruence angle.• All values medial to the zero reference line AO are

designated as minus and those lateral as plus. Mean= -6 Degrees, standard deviation = 11 degrees.

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Other Common Views:

Axial or Tunnel view of Intracondylar fossa: Taken in a prone position, will view the intercondylar fossa, and the posterior aspects of the knee joint.

x-ray beam is projected in a posterior to anterior direction

1,2 are intercondylar eminences3,4 are tibial plateaus

http://www.liv.ac.uk/HumanAnatomy/phd/mbchb/adolescent/knee2.html

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MRI

• Knee joint MRI is one of the most frequently requested imaging study in musculoskeletal radiology

• Comprehensive, non-invasive view of the meniscus, ACL, PCL, medial and lateral collateral ligaments

• Sensitivity and Specificity of 90-95% for the meniscus and almost 100% for the cruciate ligaments. (Helms, 2009)

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Images

• Sagittal Sequences give the most information on the knee– Short TE will help with

imaging the meniscus– Fast Spin Echo – proton

density (FSE-PD) do not produce acceptable images of the knee

• Fat suppression– Makes the MRI image

easier to view– Allows the Meniscal

tears to stand out easier than without the suppression.

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MRI

• Ligaments and Meniscus: image black whether it’s a T1 or T2 image.

• This MRI shows the meniscus as to triangular black blocks just under the femur.

• The patella ligament (tendon) images black from patella to tibial tubercle. http://www.fmh.org/body.cfm?id=152

http://www.fmh.org/body.cfm?id=152

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Meniscus• A fat-suppressed proton density-

weighted axial image through the knee

• Demonstrates the C-shaped menisci.

• Note the symmetrical shape of the lateral meniscus (red outline) and the asymmetry of the medial meniscus (blue outline), where the posterior horn (asterisk) is significantly larger than the anterior horn.



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• Sagittal fat-saturated proton density–weighted image:– Concave superior meniscal

surface (arrows), which improves contact with the femoral epicondyles, and a flat undersurface, which improves contact with the tibial plateau.

– The periphery (outer edges) is thicker than the central portion (arrowhead), allowing for firm attachment to the joint capsule.

– Normal bow-tie appearance of the meniscal body.




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• Coronal fat-saturated proton density–weighted image: Posterior slice – Posterior horns of the medial and

lateral menisci. The posterior horn of the medial meniscus (left arrow) is thicker than the posterior horn of the lateral meniscus (right arrow).

– The medial portion of the posterior horn of the lateral meniscus (ie, the meniscus on top of the fibula) is directed upward obliquely, from a lateral to medial direction. This is its normal course.




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Transverse (Intermeniscal) Ligament

• Axial fat-saturated proton density–weighted image

• Transverse (intermeniscal) ligament (arrows) connecting the anterior portions of the medial and lateral menisci




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The ligament of Wrisberg

• Coronal proton density–weighted image – originating from the

posterior medial horn of the medial meniscus and passing obliquely upwards (arrow) to attach to the posterolateral aspect of the medial femoral epicondyle http://emedicine.medscape.com/articl

e/399552-overview



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• Coronal fat-saturated proton density–weighted image of the mid knee

• Normal appearance of the body of the medial and lateral menisci.

• The apices (inner portions) are the thinnest part of the meniscus and are more central in the knee joint.

• The periphery, meniscal bases, outer portion (arrow and arrowhead) is the thickest part and contains the blood vessels supplying the meniscus. http://emedicine.medscape.com/articl

e/399552-overview



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ACL and PCL: Normal

Again, the ligaments willImage darker on the MRI.

Note the orientation of fibersWhen determining the Structure

These two images are takenAt different depths in orderTo see the ligaments this clearly

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ACL: Normal Views

Musculoskeletal Diseases and Disorders: Knee and Patella PTP 521.

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