The femoral trochlea is the anterior articular surface of the distal femur that articulates with the posterior surface of the patella. It consists of a central sulcus (trochlear groove) between a more prominent lateral facet and a less prominent medial facet, guiding the patella during knee flexion and extension. The trochlear groove transitions distally into the intercondylar notch. Trochlear depth (trochlear index) and sulcus angle are measured radiographically to assess trochlear dysplasia.
Trochlear dysplasia (flat or convex trochlea) is the most important structural risk factor for recurrent patellar dislocation, quantified by the Dejour classification based on sulcus depth, trochlear bump, and asymmetric facets. Severe trochlear dysplasia (Dejour type B and D) with a crossing sign on lateral radiograph requires trochleoplasty (surgical deepening of the groove) combined with MPFL reconstruction and tibial tubercle osteotomy for stabilisation. The lateral trochlear inclination angle and TT-TG distance guide the extent of bony correction required.
A shallow or convex trochlear groove fails to contain the patella during early knee flexion when the quadriceps mechanism is not yet taut, predisposing to lateral patellar dislocation; surgical correction by trochleoplasty with medial patellofemoral ligament reconstruction addresses both the bony dysplasia and the ligamentous deficiency.
Impact of the patellar articular surface against the trochlea during acute dislocation or from repetitive overloading in trochlear dysplasia produces chondral and osteochondral defects requiring microfracture, autologous chondrocyte implantation, or osteochondral transplantation depending on defect size.
