Modeling of Rotator Cuff in Shoulder Dynamics

Introduction The glenohumeral joint has a large range of motion, yet it is still stable. The joint consists of the intercalated joint surfaces of the humeral head and glenoid, along with the surrounding capsuloligamentous structures. Interaction between the capsuloligamentous structures and the articulating surfaces provides the basic static constraint of the joint. On the contrary, coordinated muscle contraction provides the dynamic balance and stability of the joint. All muscle force vectors can be resolved into compressive and shear components. The compressive force component by the muscle stabilizes the glenohumeral joint by the mechanism referred to as concavity-compression. The shear force component stabilizes the joint by direct pull. Static constraint would influence the recruitment of muscle in maintaining the equilibrium condition. The interactions between joint concavity-compression and the dynamic muscle loading are demonstrated by examining the potential abduction strength.