Ulnar Collateral Ligament (UCL) Injuries: Overview

Ulnar Collateral Ligament (UCL) Injuries: Overview

Elbow sprain is an overstretched or torn ligament in the elbow. This can happen during sports, especially when throwing, by falling onto an outstretched hand or from a hard, direct hit. The affected ligament in the elbow is called the MUCL, or medial ulnar collateral ligament, on the inside of the arm.

The injury to the MUCL may be from a sudden rupture known as acute valgus stress, or it may take some time to develop through overuse with repetitive stress into a complete rupture. This is known as chronic overload syndrome or more commonly, as pitcher's elbow. Young athletes with soft, growing bones may experience something similar called little leaguer's elbow.

Elbow sprain mainly affects the younger population, especially overhead-throwing athletes. It occurs at the most vulnerable part of a throw. At the windup, or late cocking, and acceleration phases. Throwing is the most common cause of injury to the medial ulnar collateral ligament, whether acute or chronic.

The mechanism of the injury is as follows: a force from the outside of the arm, called a valgus load, is directed on the inside of the arm. This causes a separation between the bones of the elbow. The ligament, which is a rope like fibrous structure that connects the bones, gets stretched under the stress. If the force is great enough, the ligament may rupture suddenly. If the force is more mild but repetitive, the ligament may develop small tears that worsen over time into a larger tear.

This mechanical force may even rip small pieces of bone, or osteophytes, off the attachment of the ligament. The medial ulnar collateral ligament, or MUCL, has a very important role in stabilizing the inside part of the elbow. We can see it as a very broad structure, though the valgus stress or force only affects the anterior or front portion of the three-part ligament.

It is good to notice where this ligament is attached because a very large nerve is right behind these attachments. This is the ulnar nerve, and it may be stretched and inflamed from the stress as well. This nerve innervates the pinky side of the forearm and hand.

The symptoms of an elbow strain vary depending on the severity of the injury. Symptoms due to a sudden or acute stress will be pain after an audible popping sensation, with bruising around the elbow, or ecchymosis, ulnar nerve symptoms defined by tingling, numbness, weakness, and diminishing, or atrophy of the ligament. This will translate as an immediate inability to continue playing with loss of velocity, accuracy, and throwing stamina.

Chronic valgus overuse injury was first described in javelin throwers by Warris in 1946. Patients with chronic overuse symptoms will present with medial-sided pain on the inside of the elbow, increasing in severity over time. If overuse and minor tearing persist, the pain will move towards the back side of the elbow to muscle insertions at the common flexor muscle origin with ulnar nerve symptoms and further pain due to bony breakdown or chondromalacia.

To diagnose an elbow sprain, the doctor will discuss the patient's medical history, followed by an examination of the cervical spine and the entire affected upper extremity. The examiner should check posture, any asymmetry, atrophy, or loss of muscle, edema, bruising or other deformities. The doctor will then assess function and movement with some specific tests.

The most sensitive test is called the modified moving valgus stress test, which simulates the throwing position, effectively recreating the pain to determine the test is positive. The doctor can ask for radiographic evaluation, or an x-ray, and the standard AP, or anteroposterior, lateral, and axillary or angled views of the elbow to identify degenerative changes.

CTs and MRI scans are highly sensitive and specific for detecting MUCL lesions. Typically, there will be a discontinuity of the ligament as it is torn off of its attachment site. The greyish white seen here is fluid collecting around the torn dark greyish-black ligament. Once diagnosis is complete, treatment is planned and communicated to the patient.