Lateral ankle instability as a cause of superior peroneal retinacular laxity: an anatomic and biomechanical study of cadaveric feet.

The role of the competent superior peroneal retinaculum (SPR) as a primary restraint to peroneal tendon subluxation and mechanical attritional wear is clear. Injury to the SPR has classically been described as a dorsiflexion eversion movement of the ankle coupled with a forceful peroneal tendon reflex contraction. This mechanism, however, does not cause injury to the lateral collateral ligaments of the ankle and does not explain the coexistent findings of lateral ankle instability, laxity of the SPR, and concurrent peroneal tendon pathology. Anatomic studies reveal a parallel alignment of the calcaneal band of the SPR and the calcaneofibular ligament. A cadaveric model of ankle instability created by serial sectioning of the lateral collateral ligaments revealed increasing visual strain on the SPR with increasing degrees of ankle instability. These findings suggest the SPR serves as a secondary restraint to ankle inversion stress and that the force or forces that result in chronic ankle instability can also injure and attenuate the superior peroneal retinaculum.