Patellar inversion: 180 degree rotation of the patella around its vertical axis within the intercondylar notch.

BACKGROUND

Dislocation of the patella can occur around its vertical as well as horizontal axis. However, near 180 degree rotation of the patella around its vertical axis within the intercondylar notch without its complete dislocation has never been previously reported to the best of our knowledge. We report one such neglected case along with its management.

METHODS

The patient underwent open reduction and de-rotation of patella with repair of the medial and lateral patellar retinacula. The orientation of the patellar tendon intra-operatively was used as a guide for the reduction manoeuvre required.

RESULTS

The patient had a good functional result at more than one year of follow-up.

CONCLUSIONS

A skyline view of the knee in symptomatic patients with normal AP and lateral radiographs of the knee can be useful in diagnosing a rare intra-articular dislocation of the patella around its vertical axis. Neglected cases of such injuries can be easily treated with open reduction with the orientation of the patellar tendon guiding the manoeuvre to de-rotate the patella. Careful repair of lateral and medial retinacula in such cases is important in preventing future patellar instability.