Knee Deformities Impact on Cerebral Palsy Gait

Abstract

The knee is the largest joint in the lower extremity; however, in children with cerebral palsy (CP), it generally has fewer problems then either the foot or the hip. The primary function of the knee is to allow limb length adjustment so the foot can clear the floor during swing phase and to provide stability in stance phase. At initial contact, the knee should have slight flexion, so it can participate with the ankle in absorbing the shock of weight transfer. If the knee is completely extended, it does not have smooth movement into flexion and therefore will not provide good shock absorption. These three main functions of the knee joint are controlled by muscles primarily the hamstrings for knee flexion, the quadriceps for knee extension, and the gastrocsoleus to modulate knee flexion in stance phase. Most of these muscles cross at least two joints and therefore have very complex control requirements. Due to these complex control requirements, there is often a problem in children with CP who have motor control and balance issues to properly control the time and magnitude of the muscles controlling knee motion. The goal of this chapter is to review in detail the periods in the gait cycle where these control issues are especially problematic relative to the knee motion.