Specific examination-patello-femoral joint

Inspection of the patello-femoral joint is initially best performed with the patient sitting with the leg flexed over the edge of the couch, noting the following features or signs.

  • Position of the patellae: The patella normally faces forward and slightly up. Facing higher indicates patella alta, and lower indicates patella baja.
  • Position of the tibial tubercle: This should be directly inferior to the centre of the patella. Inspection gives a guide to the tibial tubercle trochlea groove (TT-TG) offset that is more formally quantified on CT or MRI scanning.
  • Patella tracking: On active extension the patella should track centrally toward the groin. Tracking laterally in extension as an inverted J-sign indicates lateral subluxation in extension and potential or real patella instability.
  • Feeling the articulation: Holding the hand gently over the patella detects crepitus.

With the patient lying supine the following tests can be performed:

  • Detection of effusion: This has been previously described
  • Palpation for tender points:
    • Tibial tubercle for Osgood Schlatters
    • Lower pole patella for patella tendinopathy (jumpers knee) or Johansson-Sindig-Larsen syndrome in the adolescent. This is best examined by tilting the patella from superior and pushing into the lower pole with the thumb
    • Superior pole of the patella for quads tendinopathy.
    • Tenderness on the medial or lateral border of patella
    • Any specific trigger points looking for neuroma or tender nodules
    • Medial retinaculum for tenderness over the medial plica, felt as a chord on rolling the finger against the condyle (with the knee in extension)
    • Excessive patella tilt by holding the axis of the patella between finger and thumb.
  • Movements of the patella:
    • Patella glide is quantified as the proportion of patella width that it can move medially or laterally in either full extension or at 30 degrees flexion . There is debate as to what is actually normal.

Assessment of patella mobility by medial and lateral glide, expressed as a proportion of patella width that the patella moves

    • Apprehension sign. Detected by gently trying to dislocate the patella laterally, eliciting an obvious sense of apprehension by the patient. Many patients with patella instability are extremely nervous when their patella is even just approached by the examiner and this should be noted

The apprehension sign, illustrating nervousness of the patient when attempted subluxation is gently performed

    • Patello-femoral compression. Examined by compressing the patella into the groove and rocking the knee into flexion and extension, eliciting pain, catching, crepitus or bare-bone grinding.
    • Patella tendon movements. Tethering of the patella to the anterior tibia will reduce medial/lateral movement of the patella tendon.

With the knee flexed at 90ยบ, the knee is further examined.

  • Palpation for trigger point
    • Fat pad tenderness either side of the patella tendon
    • Lateral IT band syndrome. Deep tenderness 2cm proximal to the lateral joint line over the lateral epicondyle. This is then confirmed with the patient standing, facing away from the examiner and palpating over the lateral epicondyle while asking the patient to mini squat.
    • Capsular irritation over a prominent osteophytic edge of the articular surface may be noted
    • Tender nodules or points representing a neuroma or painful scar

Palpation of the knee at 90 degrees for trigger points around the patella

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