Signs of Patellofemoral Pain Syndrome
Patellofemoral pain syndrome presents with gradual onset diffuse retropatellar and/or peripatellar pain that worsens during activities requiring knee flexion under load, particularly squatting, stair descent, and running. 1, 2
Cardinal Clinical Features
Pain Characteristics
- Pain localized behind or around the patella that develops gradually rather than from acute trauma 1, 3, 4
- Pain intensifies with knee flexion during weight-bearing activities, including squatting, stair ambulation (especially descending), running, and prolonged sitting 1, 5, 6
- Diffuse retropatellar or peripatellar distribution rather than focal point tenderness 1, 2
Physical Examination Findings
- Pain with squatting bilaterally is the most sensitive physical examination finding and should be assessed in all patients 2
- Hip abductor and extensor weakness is a consistent predictor and should be assessed using hand-held dynamometry or manual muscle testing 3
- Patellar tilt or subluxation may be evident on axial radiographs 3
- Findings range from limited patellar mobility to hypermobile patella 6
Functional Limitations and Associated Features
Activity Restrictions
- Functional limitations in daily activities, sports participation, and quality of life are common presenting complaints 1, 3
- Pain typically worsens with prolonged sitting (the "theater sign") 5
- Some patients experience minor swelling and sensation that the knee "catches" or gives way 7
Psychological Comorbidities
- Patients with patellofemoral pain are six times more likely to experience anxiety or depression, which should be assessed during evaluation 1, 3
Key Distinguishing Features
What Differentiates PFPS from Other Conditions
- Gradual onset rather than sudden traumatic injury distinguishes it from acute knee pathology 3
- Pain pattern specifically related to activities involving knee flexion under load, not constant pain 5, 6
- Absence of mechanical symptoms (locking, true giving way) that would suggest meniscal or ligamentous pathology 3
- No history of acute trauma, effusion, or features suggesting fracture or dislocation 3
Clinical Pitfalls to Avoid
- Bilateral muscle deficits exist regardless of whether symptoms are unilateral or bilateral, so both limbs should be assessed even in unilateral presentations 2
- Patellar tendinopathy may coexist with patellofemoral pain syndrome and should be considered 3
- If effusion is present, consider intra-articular pathology requiring aspiration for synovial fluid analysis 3
- Osteochondral defects, loose bodies, or meniscal pathology should be considered if mechanical symptoms are present 3