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Elbow Instability (Rupture of the Medial Collateral Ligaments)

The valgus stress overload syndrome can cause medial tension resulting in torsion of the medial (ulnar) collateral ligament (MCL). This ligament, especially its anterior band, is of great importance for elbow
stability. It is composed of two parts: the origin of the anterior band is posterior to the axis of elbow rotation, while the origin of the posterior band is just posterior to the axis. The posterior portion of the MCL contributes little to valgus stability. The radial head contributes significantly to stability at 0°, 45°, and 90° of flexion, but the MCL is the most important stabilizer except at full extension. The anterior band is the major stabilizer from 20° to 120° of flexion.

Symptoms and diagnosis

– Pain on the medial side of the arm occurs during throwing (cocking phase) or serving.
– Tenderness if felt on the ligament.
– There is a sensation of the elbow ‘opening’ or ‘giving way’.
– A valgus instability is tested with a valgus stress test. The shoulder is then externally rotated, the elbow flexed 30° and a valgus load is applied. An opening of the joint indicates instability.
– A valgus instability test can be performed arthroscopically with the elbow flexed 60–70°. An opening of the joint between the ulnar and humerus can be seen. An opening of more than 0.04 in (1mm) indicates a complete tear of the ulnar collateral ligament.
– The pathophysiology involves edema (swelling) and inflammation or scar formation within the ligament.

There can also be calcific densities within the scar or ossifications within the ligament. Ruptures can also occur. These changes can be verified by an MRI.


The treatment includes rest and ice, generally followed by rehabilitation with strengthening exercises as the main focus. Surgery is indicated if 6 months of conservative therapy is unsuccessful, and occasionally in acute ruptures.

Return to sport after surgery is a test of the athlete’s patience. Although some throwing is possible after 3– 4 months, competitive throwing must be delayed for 9–12 months, and professional pitchers may need 12– 18 months before reaching full capacity.

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