Recurrent Lateral Subluxation

The typical patient is a teenage girl who becomes physically active in exercises or sports. The presenting complaint is pain in the knee in around or behind the patella especially on flexion.

There may be symptoms of giving way of knee and a swellingmight be present in the knee.  Locking and popping of the knee may also be present.

A grating sensation might occur when there is  chondromalacia.

Recurrent Dislocation

The dislocation is precipitated by sudden contraction of the quadriceps muscle  when  tibia is  in lateral rotation and the knee is in extension or slight flexion.

Diagnosis of acute dislocation is almost straightforward.

However, patient of recurrent dislocation is usually seen  between the episodes.

With knees flexed to 90 degrees, the posture of the patella will be lateral. In complete extension of the knee the patella slips medially and relocates in the femoral intercondylar groove. On flexion it is  again displaced laterally.

Apprehension test

While attempting to displace the patella laterally with the knee flexed 30 degrees and the quadriceps relaxed,exert latrally directed pressure with both thumbs pressing on the medial side of the patella.

Patient becomes fearful and uncomfortable when the patella reaches the point of maximum displacement and will resist and seize the examiner’s hand and straighten her knee to replace the patella in its relatively normal position.

This is referred to as Fairbank’s apprehension test.

Note: Try to do this test with knee extended and the sense of apprehension is not elicited. this happens because the patella moves readily on the flat condylar and supracondylar surface of the femur and not across the highest point of the lateral condyle.

Other findings that may be noted during examination are  limited  excursion of the patella medially with the knee in extension. The lateral soft tissue might be taut.

Tenderness may be elicited on compression of the patella and palpation over the medial retinaculum.

Knee defrmities like genu valgum and lateral torsional deformity of the tibia are usually present.

The patellar tendon may insert laterally with abnormal increase of the Q angle.

In case of high riding patella, the tendon may be elongated with a high-riding patella.  Hamstring spasm and knee swelling may be present