Musculo-skeletal   [back to the Category]

Traumatic patellar dislocation   [read the french version]

Author :   Docteur Anne Thiescé

Acute dislocation of the patella is a traumatic injury involving a lateral dislocation of the patella, usually coupled with a morphological anomaly of the patella or the femoral trochlea.

This is an adolescent injury in ballet that occurs during the performance of pirouettes, développés, or jumps: any movement that is carried out using a violent contraction of the quadriceps femoris, during flexion - external rotation of the knee.

Pain is very sharp, the knee collapses and the dancer falls. The dislocation usually reduces spontaneously when the dancer gets up. An haemarthrosis occurs.

Both pain and haematoma are medial lateral. This injury can go unrecognised amongst the very young.

The knee can then become painless but a feeling of instability or clicking remains.

Clinical examination often reveals a misaligned lower limb: genu valgum, recurvatum, and an external tibial hyper-rotation.

Palpation of the medial lateral edge of the patella is painful.

X-rays often show a femoro-patellar dysplasia and sometimes an abnormal lateral position of the patella which can disappear after several weeks.

X-rays sometimes identify an osteochondral fracture of the medial edge of the patella or the lateral condyle. The fragment stays attached to the medial edge of the patella or, sometimes, it is unattached in the intercondylar area.


Treatment is arguable for the first injury, either orthopaedic treatment with plaster for six weeks and re-education, or surgical treatment.

Surgical treatment is rarely questionable after a second injury. It comprises a suture of the medial patellar retinaculum, coupled with the liberation of the lateral patellar retinaculum and the ablation of osteo-cartilaginous fragments. It is carried out under arthroscopy or arthrotomy. Activities resume after 4 to 6 months, following a functional re-education.

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