What is the diagnostic approach for patella femoral pain syndrome?

Diagnostic Approach for Patellofemoral Pain Syndrome

Patellofemoral pain syndrome is diagnosed primarily through clinical evaluation based on characteristic history and physical examination findings, without requiring imaging in most cases. 1, 2

Clinical History - Key Features

The diagnosis centers on identifying specific pain patterns and functional limitations:

• Gradual onset diffuse retropatellar and/or peripatellar pain that worsens with activities such as squatting, stair ambulation (especially descending), and running 1
• Pain develops gradually rather than suddenly, distinguishing it from acute traumatic injuries 1
• Functional limitations in daily activities, sports participation, and quality of life are common presenting complaints 1
• Overuse patterns and training errors are important historical risk factors to identify 3
• Assess for psychological comorbidities, as patients with patellofemoral pain are six times more likely to experience anxiety or depression 1

Physical Examination - Specific Findings

The physical examination should focus on identifying biomechanical contributors and tissue-specific pain sources:

Strength Assessment

• Hip abductor and extensor weakness is a consistent predictor of patellofemoral pain syndrome and should be assessed using hand-held dynamometry or manual muscle testing 1, 2
• Quadriceps weakness, particularly vastus medialis obliquus, is a key risk factor 3
• Perform functional testing including single-leg squat to observe movement patterns and identify weakness 1, 2

Patellar Alignment and Mobility

• Q angle measurement using a standardized protocol has shown value as a predictor when performed consistently 2
• Assess for lateral patellar tilt, though evidence for its reliability as a standalone predictor is inconsistent 2
• Evaluate tissue tolerance to load through pain provocation tests and presence of effusion 4

Additional Examination Elements

• Crepitus on patellar motion is a supported predictor of patellofemoral pain syndrome 2
• Assess for soft-tissue tightness, particularly lateral retinacular structures and iliotibial band 3
• Clustering multiple physical examination findings provides better sensitivity and specificity than individual tests alone 2

Imaging - When and What to Order

Imaging is not required for initial diagnosis but has specific indications:

Initial Imaging

• Radiographs of the knee are usually appropriate for initial evaluation in patients ≥5 years of age with chronic knee pain 5
• Standard views should include anteroposterior, lateral, and axial radiographs to demonstrate patellar tilt or subluxation 5

Advanced Imaging Indications

• MRI without IV contrast may be indicated when radiographs demonstrate small osseous fragments along the medial patellar margin or if there is clinical concern for patellar dislocation-relocation 5
• If no improvement after 6-8 weeks of consistent conservative therapy, reassessment of diagnosis and consideration of imaging to rule out other pathologies (osteochondral defects, loose bodies, meniscal tears) may be necessary 1
• CT without IV contrast may be indicated to evaluate patellofemoral anatomy in the setting of chronic pain related to repetitive patellofemoral subluxation 5

Emerging Diagnostic Tools

• Musculoskeletal ultrasound shows promise for identifying decreased vastus medialis obliquus volume, asymmetry in gluteus medialis thickness, intra-articular effusions, and quadriceps/patellar tendon thickening 2
• Ultrasound has the advantage of providing dynamic examination of the patellofemoral joint 2

Common Diagnostic Pitfalls

• Overemphasis on imaging without adequate trial of conservative management is a common error 1
• Relying on single physical examination tests rather than clustering findings leads to lower diagnostic accuracy 2
• Failure to assess hip strength can miss a critical biomechanical contributor 1
• Not evaluating for psychological comorbidities may result in incomplete treatment planning 1

Differential Considerations

When the diagnosis is unclear or patients fail to respond to treatment, consider:

• Osteochondral defects or loose bodies requiring MRI evaluation 5
• Patellar tendinopathy (enthesopathy) which may coexist 4
• Meniscal pathology in patients with mechanical symptoms 5
• Intra-articular pathology if effusion is present, potentially requiring aspiration for synovial fluid analysis 5