The two primary ligaments that restrict side-to-side (varus and valgus) movements of the elbow joint are the ulnar collateral ligament (UCL) and the radial collateral ligament (RCL).
Ulnar Collateral Ligament (UCL)
The Ulnar Collateral Ligament (UCL), located on the medial (inner) side of the elbow, is crucial for resisting valgus stress. Valgus stress occurs when the forearm is forced outward relative to the upper arm. The UCL is frequently injured in throwing athletes due to repetitive valgus forces.
Radial Collateral Ligament (RCL)
The Radial Collateral Ligament (RCL), situated on the lateral (outer) side of the elbow, provides stability against varus stress. Varus stress happens when the forearm is forced inward relative to the upper arm. The RCL complex also assists in resisting posterolateral rotatory instability. It originates from the lateral epicondyle of the humerus.
In summary, the UCL protects the elbow from excessive outward movement, while the RCL safeguards against excessive inward movement, thus contributing significantly to the overall stability of the elbow joint.
