The MPFL is the primary passive restraint preventing lateral patellar dislocation, providing 50 to 60 percent of the total medial stabilising force at 0 to 30 degrees of knee flexion before the trochlea takes over as the primary guide. It is torn in virtually all first-time patellar dislocations (over 90 percent). MPFL reconstruction has become the standard surgical treatment for recurrent patellar instability, replacing the older lateral retinacular release procedures.
| Origin | Medial femoral epicondyle and adductor tubercle |
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| Insertion | Superomedial patella (medial third of the superior patellar surface) |
| Actions | Primary restraint against lateral patellar dislocation — provides approximately 50 to 60 percent of the medial patellar restraint force |
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MPFL tears are identified on MRI as signal changes or complete disruption at the femoral attachment, the patellar attachment, or within the ligament substance. The femoral attachment tear is most common and corresponds to the anatomical landmark 1 cm anterior and 2.5 mm distal to the adductor tubercle, the critical reference point for MPFL reconstruction graft placement. Failed MPFL reconstruction from incorrect femoral tunnel placement is the most common technical error in patellar instability surgery.
Medial patellar restraint disruption in lateral patellar dislocation, reconstructed with gracilis or semitendinosus autograft for recurrent instability with femoral tunnel placement at the anatomical attachment point.
