User:CPP312

Anatomy and Mechanism
The ulnar collateral ligament (UCL, also known as medial collateral ligament) is located on the medial side of the elbow. The UCL complex is comprised of three ligaments: the anterior oblique, posterior oblique and transverse ligaments. The anterior oblique ligament (AOL) attaches from the undersurface of the medial epicondyle to the medial ulnar surface slightly below the coronoid process. It is the sturdiest of the three sections within the UCL. The AOL acts as the primary restraint against valgus stress at the elbow during flexion and extension. The posterior oblique originates at the medial epicondyle and inserts along the mid-portion of the medial semilunar notch. It applies more stability against valgus stress when the elbow is flexed rather than extended. The transverse ligament connects to the inferior medial coronoid process of the ulna to the medial tip of the olecranon. Since it is connected to the same bone and not across the elbow joint, the transverse ligament has no contribution to the joint’s stability.

Injury Mechanism
The UCL is important because it stabilizes the elbow from being abducted. If intense or repeated bouts of valgus stress occur on the UCL, injury will most likely transpire. Specific overhead movements like those that occur during baseball pitching, tennis serving or volleyball spiking increase the risk of UCL injury. During the cocking phase of pitching, the shoulder is horizontally abducted, externally rotated and the elbow is flexed. There is slight stress on the UCL in this position but it increases when the shoulder is further externally rotated. The greater the stress the more the UCL is stretched causing strain. However, the majority of valgus stress occurs during the acceleration phase of pitching. In this phase, the body is brought forward leaving the arm to follow. Then, the shoulder is forcefully internally rotated, whipping the humerus forward which leaves the forearm behind. This causes tremendous valgus stress and tensile strain on the UCL. Poor mechanics along with high repetition of these overhead movements can cause irritation, micro-tears or ruptures of the UCL.