Four important synovial joints used in most sporting actions are the elbow and shoulder joints in the arm, and the knee and hip joints in the leg. The elbow and knee joints are both hinge joints.

Elbow Instability: A condition where the elbow joint is unable to maintain its normal ... and have systems in place to gain human feedback on the overall quality of the process.

Flexion – bending a joint. This occurs when the angle of a joint decreases. For example, the elbow flexes when performing a biceps curl. Extension – straightening a joint. This occurs when the ...