Patellofemoral Pain Syndrome: A Diagnostic Analysis

Clinical Question:

What is the best diagnostic procedure to identify the true presence of the patellofemoral pain syndrome?

Evidence Used

Data Sources: Pubmed, Google Scholar
Search Terms: "patellofemoral pain syndrome" AND/OR "diagnosis" AND/OR "physical therapy" AND/OR "diagnostic tests" AND/OR "medical imaging"

Inclusion Criteria: meta-analyses; systematic reviews; studies that included likelihood ratios, and sensitivity and specificity values.
Exclusion Criteria: case studies; studies that didn't test for likelihood ratios, and sensitivity and specificity values.

Background Information

Physical Therapy Relevance
Patellofemoral Pain Syndrome is listed as the second most common musculoskeletal diagnosis of the that presents in the physical therapy clinic. It has been reported to account for roughly 25% of the population. (1)

Description of PFPS

Anterior or retropatellar pain that is provoked by sitting for long periods of time, climbing or going down stairs and squatting and with no other outstanding pathology. (2)

Subjective Information


  • Anterior Knee Pain (4)
    • Increased with higher compressive forces associated with certain movements
      • Ascending/descending stairs
      • Sitting with knees bent
      • Kneeling
      • Squatting

Risk Factors (5)

  • Female adolescents
  • Younger physically active adults

Mechanism of Injury (6)

  • The cause of PFPS is unknown
  • Suggested causes include:
    • Lower extremity malalignment
    • Muscular imbalances
    • Lateral retinaculum tightness
    • Disruption of cartilage
    • Increased Q angle
    • Overuse
    • Abnormal mechanics of the hip

Differential Diagnosis (4)

  • Patellar tendinitis
  • Osteoarthritis in the knee
  • Medial meniscus tears
  • ACL Tears
  • PCL tears

Objective Information

Physical Examination (2)
  • Observation and palpation of the knee
    • Abnormal tracking of the patella can cause pain and tissue stresses
    • A positive result of abnormal patellar tracking would lead to a suspicion of PFPS
    • Examiner would continue with further special testing

Joint Kinematics (3)
  • The patella glides along the patellar surface of the femur.
    • With flexion, the patella will glide inferiorly and medially.
    • With extension, the patella will glide superiorly and laterally

In NJ Macintyre's study, Patellofemoral Joint Kinematics In Individuals With And Without Patellofemoral Pain Syndrome, the researchers found that during knee flexion there was a significant change in patellar position between the two groups. The study concluded that at 19° of knee flexion the patella tracks on average 2.25mm more laterally in the individuals with patellofemoral pain syndrome compared to those without.

Objective Tests for Patellofemoral Pain Syndrome

Waldron’s test (2)
  • Description: For phase I, the patient is in the supine position. The examiner presses the patella against the femur while performing passive knee flexion. For phase II, the patient is standing and performs a slow, full squat while the examiner gently presses the patella against the femur.
  • Positive finding: pain and crepitus
  • Sensitivity: 45% (5)
  • Specificity: 83% (5)
  • Positive Likelihood Ratio: Phase 1 = 1.0; Phase II = 1.05 (5)

Phase I:

Phase II:

Eccentric step test (2)

  • Description: Each patient should be barefoot when performing this test. A step adjust to 50% of the height of the patient’s tibia (to standardize step height). The patient is given a demonstration and the instructions to stand with both feet on the step with their hands on their hips. First step down with the involved leg and then back up onto the stool. Then step down with the uninvolved leg, leaving the involved leg to support their weight on the stool.
  • Positive finding: Pain during this test was considered positive
  • Sensitivity: 42% (5)
  • Specificity: 82% (5)
  • Positive Likelihood Ratio: 2.3 (5)

Clarke’s test (also patellofemoral grinding test) (2)

  • Description: Patient should be in supine with their knees flexed. Add knee pad support under the knees to achieve flexion. This will cause the patella to articulate. With the patient relaxed, the examiner will place their hand on the superior border of the patella and push it distally. While the patella is inferiorly displaced, the examiner will then ask the patient to contract their quadriceps.
  • Positive finding: If pain is elicited with the contraction of the quadriceps while the patella is manually displaced distally.
    • False positives can be found if knee is left in extension by potentially pinching the suprapatellar pouch.
  • Sensitivity: 48% (5)
  • Specificity: 75% (5)
  • Positive Likelihood Ratio: 1.9 (5)

Vastus Medialis Coordination Test (2)

  • Description: Patient is in the supine position and the examiner’s fist is underneath the patient’s knee. Patient extends his/her knee fully without pushing leg into or lifting it away from the examiner’s hand.
  • Positive finding: lack of coordinated, full extension i.e. the movement was not smooth or the patient compensated with hip flexors or extensors
  • Sensitivity: 16% (5)
  • Specificity: 93% (5)
  • Positive Likelihood Ratio: 2.26 (5)

Patellar apprehension test (2)

  • Description: The patient is in the supine position. The examiner applies a lateral glide to the patella while pushing the patient’s leg into hip and knee flexion.
  • Positive finding: apprehension or reproduction of pain
  • Sensitivity: 32% (5)
  • Specificity: 86% (5)
  • Positive Likelihood Ratio: 2.3 (5)

Medical Imaging (7)

MRI - 16 studies of “high quality”

If the previously described five objective tests render inconclusive results, an MRI is suggested to determine if the patient has patellofemoral pain syndrome. The following anatomical characteristics found on MRI scans have been correlated with a positive diagnosis of Patellofemoral Pain Syndrome. They are listed in order from highest association to lowest association.

Stepwise systematic approach summary (8)

  • Assess patella alta/baja. Also assess anterior fat pads and trochlear cartilage
    • Ratio is taken between the length of the patellar tendon to the length of the patella (9)

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  • Assess lateral patellar tracking along the femur and grade as mild, moderate, or severe. Also assess the medial translation.
    • Grades assessed distance between median ridge of the patella and apex of the trochlear sulcus - should match if no translation
      • Mild: <5mm
      • Moderate: 5-10mm
      • Severe: >10mm
  • Assess patellar tilt using the patellofemoral angle.
    • Normal patellofemoral angle is >8° and opens laterally
    • Medial opening or a patellofemoral angle of <8° is considered abnormal
  • Assess for trochlear sulcus hypoplasia/dysplasia using trochlear sulcus angle and depth.
    • Sens: 100%, Spec: 96% if, trochlear sulcus measures 3mm or less at 3 cm above the TF articulation
    • Hypoplasia: sulcus angle greater than 144 deg, sulcus depth less than 5 mm
    • Dysplasia: Sulcus depth less than 3 mm
  • Assess the Tibial Tuberosity to the Trochlear Groove distance, particularly if there is suspected lateralized tibial tuberosity/patellar tendon transposition.
    • Greater than 15mm is linked to more lateral translation of the patella
  • Assess for soft tissue abnormalities in relation to the patellar tendon, the quadriceps muscles and tendon, the patellar retinaculum, and the fat pads.
    • Assess for general abnormalities

Other Imaging Techniques

Other methods of imaging including computerized tomography, ultrasound and x-ray have all been found to have either a decreased quality of results or unsatisfactory results regarding the diagnosis of Patellofemoral Pain Syndrome.

  • CT - 8 studies of “moderate quality”
    • With 15 degrees of knee flexion it was found that patients had greater pain with quad contraction compared to those without contraction.
  • Ultrasound - 4 studies of “high quality”
    • A meta-analysis determined that there was no significance after pooling of the studies. When looking at the studies without pooling there was limited evidence to support findings across them.
  • X-ray - 3 studies of “high quality” and 2 of “moderate quality”
    • A meta-analysis determined that there was no significance after pooling of the studies. When looking at the studies without pooling there was limited evidence to support findings across them.

Clinical Toolbox Gadget

This chart is used to determine the diagnosis of PFPS based on a specific sequence of special tests and imaging performed on a patient. The chart begins with the most specific special test, and if the results are positive then the most likely condition is PFPS. However, if the test produces a negative result, the examiner will continue through the chart to the next test of lower specificity and higher sensitivity (a higher risk of Type 1 error). If those tests appear positive, the examiner is then suggested to use MRI imaging technology to examine different characteristics of the knee to avoid false positives. The list of MRI characteristics is organized based on the abnormal aspects of the knee that are most commonly seen in patients with PFPS. The MRI sequence described in the chart, along with the special tests that rendered positive results can give the examiner a combination of diagnostic factors to determine whether or not the patient has PFPS.

This tool would benefit from research over the MRI characteristics and their correlation with a diagnosis of PFPS.

Patellofemoral Pain Syndrome Clinical Assessment Tool - Page 1 (1).png

  1. Wilson T. The Measurement of Patellar Alignment in Patellofemoral Pain Syndrome: Are We Confusing Assumptions With Evidence? Journal of Orthopaedic & Sports Physical Therapy. 2007;37(6):330-341. doi:10.2519/jospt.2007.2281.
  2. Nijs J, Geel CV, Auwera CVD, Velde BVD. Diagnostic value of five clinical tests in patellofemoral pain syndrome. Manual Therapy. 2006;11(1):69-77. doi:10.1016/j.math.2005.04.002.
  3. Macintyre NJ, Hill NA, Fellows RA, Ellis RE, Wilson DR. Patellofemoral Joint Kinematics In Individuals With And Without Patellofemoral Pain Syndrome. The Journal of Bone and Joint Surgery-American Volume. 2006;88(12):2596-2605. doi:10.2106/00004623-200612000-00006.
  4. Zuma K, Bakalli F, Desantoine Q, Thomas E, Robertson C. Patellofemoral Pain Syndrome. Physiopedia. Accessed April 4, 2017.
  5. Nunes GS, Stapait EL, Kirsten MH, Noronha MD, Santos GM. Clinical test for diagnosis of patellofemoral pain syndrome: Systematic review with meta-analysis. Physical Therapy in Sport. 2013;14(1):54-59. doi:10.1016/j.ptsp.2012.11.003.
  6. Cook C, Mabry L, Reiman MP, Hegedus EJ. Best tests/clinical findings for screening and diagnosis of patellofemoral pain syndrome: a systematic review. Physiotherapy. 2012;98(2):93-100. doi:10.1016/
  7. Drew B, Redmond A, Smith T, Penny F, Conaghan P. Which patellofemoral joint imaging features are associated with patellofemoral pain? Systematic review and meta-analysis. Osteoarthritis and Cartilage. 2016;24(2):224-236. doi:10.1016/j.joca.2015.09.004.
  8. Chhabra A, Subhawong TK, Carrino JA. A systematised MRI approach to evaluating the patellofemoral joint. Skeletal Radiology. 2010;40(4):375-387. doi:10.1007/s00256-010-0909-1.
  9. De Bie N, Cami F, Ritchie L, De Pot J, O'Reilly N. Patella alta. Physiopedia. Accessed April 6, 2017.