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