Lower limb prosthesis with means for restricting dorsi-flexion

Abstract

In a lower limb prosthesis an energy storing foot is combined with a resilient ankle joint which is arranged to allow planatar flexion but substantially to prevent dorsiflexion. The ankle joint comprises a ball and socket joint, the socket of which is extended downwardly on the anterior, medial and lateral sides to for a skirt positioned so as to compress a resilient ring encircling a ball member of the ball and socket joint. Metal plates are embedded in the anterior part of the ring to prevent significant dorsiflexion. The foot has a keel having a lower spring portion connected at its posterior end as a cantilever to an upper ankle mounting portion. These two portions may be formed as a single carbon fibre reinforced plastics moulding or individually as part of a two-piece keel with the ankle mounting portion rigid and the spring portion as simple fibre-reinforced strip. The resilience of the foot is adjustable by means of a displaceable resilient buffer element mounted ahead of the ankle centre as a coarse adjustment device and/or by means of a transversely extending support bar which can be moved longitudinally behind the ankle centre by rotating an adjusting screw. The screw passes through an aperture in the keel and is accessible at the rear of the heel.