Abstract: A leg prosthesis is disclosed which incorporates a novel spring-biased telescopic shank permitting amputees to run and take part in a variety of sports such as volleyball and basketball. The shank includes a spring and damper piston which absorb ground impact forces shortening the shank at heel-strike minimizing the impact on the amputee's stump. At toe-off the spring recoils to restore the original length of the limb and provides impetus to accelerate the prosthetic leg so that full extension of the leg occurs prior to the next heel-strike. The shank can be prestressed for use with amputees of different weight and can be readily fitted to conventional prosthetic feet and knees.