Knee and ankle kinesiology and joint instability

Abstract: This study, comprising 7 separate papers, is concerned with the additional information supplied by a kinesiological approach for evaluation of patients with instability due to old ligamenta us injury to the knee or ankle joint. This approach required development of new methods for kinesiological analysis. Impaired performance in patients with old anterior cruciate ligament (ACL) rupture was mainly found in tests which greatly stress the knee joint, ie figure-of-eight running and one-legged jump for distance. A scaling model approach was constructed and found appropriate in evaluating knee and ankle function in patients with ligarnentous injuries. A dynamic, two-dimensional, biomechanical model was developed and implemented in a motion analysis system together with a force plate and EMG. This model was found useful for evaluation of kinematics, kinetics and muscular activation patterns at the ankle, knee and hip joints during functional movements such as walking and jumping. A movement analysis could reveal adapted movement- and muscular activation patterns for the ACL-deficient knee compared to the noninjured at touch down at one-legged jump. An internal knee model disclosed a simultaneous decrease in sagittal shear load which was interpreted as an adaptation to avoid increased intrinsic joint movements or gross subluxations. Unilateral injury to the lateral ligaments of the ankle is related to both ipsi- and contralateral functional alterations. There is a risk of underestimating the impairment of the injured joint in a function test using the noninjured side as a reference. A perturbation device was construcred and found useful for the analysis of postural strategies, reaction latencies and ankle joint function during single limb stance. The ankle joints were found to be of primary concern for postural corrections to retain equilibrium in single limb stance. A quasi static, three-dimensional ankle model was developed and implemented in a motion analysis system which made possible study of ankle joint function, load and instability. Different motor patterns were found for the functionally unstable foot compared to the stable in single limb stance.