From the Guidelines
Patellofemoral pain syndrome (PFPS) is diagnosed primarily through clinical evaluation, focusing on a thorough history and physical examination, as imaging studies often appear normal. The diagnosis begins with a thorough history focusing on anterior knee pain that typically worsens with activities like climbing stairs, squatting, or sitting with knees bent for prolonged periods 1. Physical examination includes assessment of patellar tracking, quadriceps strength, and specific provocative tests such as the patellar compression test and Clarke's sign. The examiner may also evaluate for anatomical factors like Q-angle abnormalities, foot pronation, or muscle imbalances.
Key Diagnostic Criteria
- A thorough history of anterior knee pain
- Physical examination of patellar tracking and quadriceps strength
- Provocative tests such as the patellar compression test and Clarke's sign
- Evaluation of anatomical factors like Q-angle abnormalities and foot pronation While X-rays are often normal, they may be ordered to rule out other conditions, showing potential lateral patellar tilt or subluxation in some cases 1. MRI is rarely needed but might be used to exclude other pathologies when the diagnosis remains unclear.
Differential Diagnoses
- Patellar tendinopathy
- Meniscal tears
- Early osteoarthritis The diagnosis is confirmed when other knee pathologies are excluded and the patient's symptoms and examination findings align with the typical presentation of patellofemoral pain syndrome. According to the most recent study 1, a comprehensive assessment should include objective evaluation of physical impairments, such as muscle strength, movement patterns, and tissue tolerance to load, as well as consideration of contextual factors related to symptoms. Education should underpin any intervention, adjusted to reflect the needs of the person, and may seek to challenge inaccurate beliefs, build confidence, and promote autonomy 1.
From the Research
Diagnostic Criteria for Patellofemoral Pain Syndrome (PFPS)
The diagnostic criteria for PFPS include:
- A thorough history to identify the date of symptom onset, mechanism of injury and/or antecedent events, location and quality of pain, exacerbating and alleviating symptoms, relevant past medical history, occupational demands, recreational activities, footwear, and patient goals 2
- Physical examination to identify the patient's specific impairments, assessing range of motion (ROM), muscle length, effusion, resisted isometrics, strength, balance and postural control, special tests, movement quality, palpation, function, and patient reported outcome measures 2
- Objective assessments to guide treatment, progression, and clinical decision-making 2
Physical Examination Maneuvers
Physical examination maneuvers used to diagnose PFPS include:
- Q angle measurement 3
- Patellar tilt 3
- Crepitus 3
- Strength and functional testing 3
- Physical examination maneuver clustering 3
- Musculoskeletal ultrasound (US) to evaluate the patellofemoral joint and surrounding tissues 3
Predictors of PFPS
Predictors of PFPS include:
- Q angle (when measured utilizing a standardized protocol) 3
- Crepitus 3
- Weakness of hip abductors and extensors 3
- Weakness detected in functional testing 3
- Decreased vastus medialis obliquus (VMO) volume 3
- Asymmetry in gluteus medius thickness 3
- Intra-articular effusions 3
- Quadriceps and patellar tendon thicknesses 3
Limitations of Diagnostic Criteria
The reliability of most physical examination tests alone remains low, but clustering physical examination findings may provide better sensitivities and specificities in diagnosing PFPS 3. Further studies are needed to establish the gold standard for diagnosing PFPS and what US findings are truly predictive of PFPS 3.