[Surgical treatment of non-osteoarthritic femoropatellar diseases].

Patellar instability, associated with varying degrees of pain, is the major symptom of non-osteoarthritic femoropatellar diseases. This patellar instability is due to either mechanical (femoropatellar "derailment") or pain (due to chondropathy) disruption of quadriceps function. The result of surgical treatment of painful femoropatellar instability, regardless of its type, is governed by the same postoperative factors. A good result can only be obtained when the postoperative TA-GT lies within a certain range of the ideal value which varies according to the trochlear angle; the quality of the result essentially depends on the postoperative height of the patella. Preoperative radiological measurement of the trochlear angle on femoropatellar views in 30 degrees of flexion, of the TA-GT angle in 30 degrees of flexion and the height of the patella is therefore necessary to select and modulate the therapeutic procedures designed to treat non-osteoarthritic femoropatellar diseases.