Internal Impingement Shoulder Injuries Overview

Internal shoulder impingement is a condition that primarily affects throwing athletes.

This condition affects the following structures:

• The posterior labrum: The labrum in the posterior-superior region of the shoulder is often frayed or partially torn. In more severe cases, a SLAP tear can develop, which is a tear that extends up towards the attachment of the biceps tendon.
• The rotator cuff: A partial-thickness rotator cuff tear affects the undersurface of the rotator cuff.

The problem is caused by pinching between the tuberosity (top of the humerus) against the labrum. Internal shoulder impingement inhibits internal rotation, which is the ability to fully rotate the shoulder inward.

Signs of Internal Impingement

The most common signs of this problem include:

• Pain when throwing in overhead sports (such as tennis serves)
• Tenderness on the front of the shoulder (pectoralis minor tendon/coracoid process)
• Tenderness around the scapula and the posterior shoulder capsule

You may notice that you have difficulty reaching up high to the back on your affected side in comparison to your unaffected side. 

Typically, shoulder mobility is slightly abnormal during a physical examination. Specifically, with internal shoulder impingement, you might have more external rotation than expected (which is common in throwing athletes) and slightly decreased internal rotation. 

And you can have subtle instability of your shoulder joint. The instability of the shoulder is thought to be a key component of why internal impingement develops.

Diagnostic tests may include a shoulder X-ray, which is usually normal. An MRI generally shows some bone bruising (edema) at the ball-and-socket shoulder joint, a partial thickness tear of the rotator cuff, and/or damage to the labrum (although not typically a detachment of the labrum).

Treatment Options

Treatment usually starts with noninvasive strategies to address the problems in shoulder mechanics. The focus of treatment is to regain normal shoulder rotation and to improve the movement of the scapula throughout the shoulder range of motion.

A physical therapist or trainer can work with you to reach this goal. Conservative management helps the vast majority of the time, even for high-level athletes.

If you don’t improve despite a focused effort on therapy, you might consider having arthroscopic shoulder surgery. Generally, surgery is done to repair damage to the rotator cuff or the labrum, and also to address any subtle instability of the shoulder joint that may be contributing to the problem.