Anterior Knee Pain Syndrome
James Barsi, MDAssistant Professor of Orthopaedic Surgery
June 14, 2013
Anterior Knee Pain Syndrome
• Pain with prolonged knee flexion or stairs
• Vague, localized in peripatellar area
Background
• Diagnosis and treatment is challenging
• “Anterior knee pain syndrome” groups together different but related pathologic entities
Anterior Knee Pain Syndrome
Sharp, intermittent pain:Loose bodies
Unstable chondral damage
Constant Pain, not activity related:
Sympathetic dysfunctionNeuroma
Referred radicular painSecondary Gain
Activity Related Patella tendonitis
ITB syndromePlica syndrome
Fat pad syndromeArthosis
ChondromalaciaInflammatory arthritis
Patella InstabilityMalalignment Syndromes
Pain
• Free nerve endings are concentrated in the patella tendon, retinaculum, fat pad1
• Patients with AKPS have perivascular proliferation of nociceptive axons in retinaclum2
• Substance P nerve fibers are widespread within the soft tissues around the knee (retinaculum, synovium, fat pad). In patients with AKPS, more Substance P fibers were found in the fat pad and retinaculum3
(1) Biedert et al. Am J Sports Med 1992; 20: 430.(2) Sanchis-Alfonso et al. Am J Sports Med 1998; 26;703(3) Witonski et al. Knee Surg Sports Traumatol Arthrosc 1999; 7:177-183
Clinical Evaluation
• Not all anterior knee pain associated with patella alignment abnormalities
• Radiographic findings not pathologic if patient not symptomatic
Physical Examination
• Observation
• Alignment
• Varus/Valgus
• Rotational
• Patella tracking
• Pes planus
Physical Exam
• Patella apprehension
• Tight lateral retinaculum
• Quadriceps and hamstring tightness
• Hip strength
Radiographs
• AP, lateral, Merchant axial view
• Patella sitting centered in trochlea
• Tilt
• Trochlea morphology
Predictors of Pain
• 282 adolescents
• 10% Patellofemoral Pain
• Predictors of developing pain:
• Decreased flexion of quadriceps, gastrocnemius
• Increased VMO response time
• Decreased explosive strength
• Increased thumb to forearm mobility
1. Witvrouw et al. Am J Sports Med 2000; 28: 480.
Role of the Hip
• Hip extensors absorb 25% energy during landing
• Deficits in hip strength add to load on the knee.1
1. Zhang et al. Med Sci Sports Exer 2000; 32: 812.
Nonsurgical Management
• Physical Therapy
• Knee Brace
• Orthotics
Physical Therapy
• Traditional concept of trying to achieve isolated VMO strength not supported by literature.
• Closed vs open chain:
• Both types produced improvements in strength, pain relief and return to function1
1. Witbrouw et al. Am J Sports Med 2000; 28: 687.
Does Physical Therapy Help?
• 84% of patients improved after 8 weeks of quadriceps & hip rehabilitation.
• 75% of patients maintain improvement 6 months to 7 years2
1. Doucette et al. Am J Sports Med 1992: 20: 434.2. Kannus et al. JBJS 1999; 81: 355-363
Physical Therapy
• Attention should be paid to quadriceps flexibility
• Strengthening done without causing pain
• Emphasis on hip strengthening
• Continued until plateau reached
Surgical Management
• Surgery is not necessary in most cases
• Successful surgical treatment requires an accurate diagnosis (patella instability or patellofemoral malalignment)
• Normal alignment and no instability may be symptomatic from tendinosis in the quadriceps or patella tendons, pathologic hypertrophy and inflammation in the medial plica
• Damage to the articular surface may also cause pain
Chondroplasty
• Arthroscopic debridement of grade 2 and 3 chondral lesions can be useful
• 58% good or excellent results with traumatic onset
• 41% good or excellent results with atraumatic onset1
1. Federico et al. Am J Sports Med 1997; 25: 663-669
Lateral release• Effective in treating a well-defined subset of
patients
• Mechanism
• relieves pressure in lateral retinaculum
• divides neuromatous nerves in the retinaculum
• relieves pressure on the lateral facet of the patella
Lateral Release• Ideal patient
• No instability
• Tight lateral retinaculum
• Outcome related to chondral damage
• 59% satisfactory with >grade 31
• 92% good to excellent with < grade 22
1. Aderinto et al. Arthroscopy 2002; 18:399-4032. Shea et al. Arthroscopy 1992; 8:327-334.
Complications of Lateral Release
• Persistent pain
• Worsening instability
• Suspect medial subluxation in any patient reporting persistent pain after lateral release
• Test in decubitus with lateral knee up, patella sags medially from gravity
• Patient unable to flex knee
Tibial tubercle transfer• Lateral patellar tilt and subluxation
• Results correlated to location of patella chondral lesions
• global and proximal lesions did less well
• Biomechanical studies show that transfer while decreasing overall load, transfers it disproportionally to proximal patella
Cartilage Restoration
• OATS and autologous chondrocyte implantation
• Small numbers have been reported and reports are mixed
• Less aggressive procedures (chondroplasty, microfracture or abrasion) may be equally effective
Patellofemoral Arthroplasty
• Low demand patients
• Care at the time of surgery to ensure extensor mechanism is aligned
Summary
• Important to establish accurate diagnosis
• Non-surgical management remains the most predictable method of treatment
Thank You