The goal of this study is to perform force and stability assessment of the elbow joint. The goal will be accomplished by integrating the results from three closely related studies. Muscle Force and Combined Joint Force will be calculated using an analytic model for ideal loading conditions, as well as activities of daily living. Elbow joint configuration and loading conditions on the forearm of normal subjects during these activities will be measured and this information used as input for force calculation. We propose to complete verification of force results of normal subjects involved in activities of daily living using electromyography. Restraining Functions of Capsules and Ligaments will be obtained using an analytical model based on locations of origin and insertion and material properties of ligaments. Experimental results from stiffness tests under controlled displacements using a material testing machine will be used to provide data and verification of the analytical model. Force on Articular Surfaces will be determined under a wide variety of conditions using an analytic model based on the geometry of the articular surface and ligamentous constraints. Furthermore, pressure distribution on these contact areas will be calculated using the rigid body-spring model analysis. Experimentally, the location of contact area will be determined using silicone casting. Ultimately, this project should provide essential information about elbow biomechanics which can be applied to controversial and unsolved clinical problems: 1) clinical setting in which the radial head or olecranon may be safely excised; 2) anatomical and mechanical features of the diseased joint that dictate the proper selection of a resurfacing or semiconstrained joint replacement device; and 3) relative contribution of the articulation and soft tissues to the mechanism of the most common complication of elbow injury--joint contracture.