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Wheeless' Textbook of Orthopaedics

Examination of the Patellofemoral Joint


- See:
      - Knee Exam
      - Patellar Malalignment

- Exam:
    - hemarthrosis
    - ligamentous laxity:
         - persons at risk for patellar instability may exhibit generalized ligamentous laxity & poorly developed vastus medialis;
         - if hyperlaxity is present, consider collagen disorder
    - patellar position:
         - when these patients are sitting or standing erect in a relaxed position patellae often faces laterally (owls eye patella);
         - "J sign" - refers to lateral patellar deviation during terminal knee extension;
    - quadriceps contracture:
         - will cause a reverse "J" sign w/ habitual dislocation of the patella in flexion;
    - patellar displacement: (Sage sign)
         - the patella can normally be manually displaces both medially and laterally between 25% and 50% of width of the patella;
         - greater movement indicates loose patellar restraints, a finding frequently seen in adolescent females;
         - w/ pt sitting & knees flexed to 90 deg, lateral position patella sometimes can be seen;
    - patellar compression test:
          - this test attempts to correlate anterior knee pain w/ articular degeneration;
          - the surgeon compresses the patella down into the trochlear groove as the patient flexes and extends the knee;
    - apprehension test:
         - examiner holds the relaxed knee in 20 to 30 deg of flexion, & patella is manually subluxed laterally;
    - Q angle:
         - this is best measured both w/ the knee in extension as well as flexion;
         - the Q angle may not be accurrate in extension, since a laterally dislocated patella may give the false impression that the Q angle is normal;
               - in flexion, this is not a problem since the patella is well seated in the trochlear groove;
    - patellar tilt test:
         - w/ knee in 20 deg of flexion, the examiners thumb attempts to flip the lateral edge of the patella upwards;
              - a patient w/ an excessively tight lateral retinaculum, will have almost no upward movement as compared to the opposite side;
              - normally the patella can be tilted upwards above the horizontal;
    - medial patellofemoral ligament
              - look for tenderness at the femoral origin of the MPFL (as well as tenderness from its patellar origin);
              - a lateral gluide greater than 75% of the patellar width is abnormal



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Friday, August 31, 2012 9:22 am