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Ball-and-Socket Sensibilities

Shoulder instability

You use your shoulders during chest, back and, of course, shoulder training and even on some leg exercises. The shoulder joint is unique. Its shallow, bony socket makes for a great range of motion, but loading that joint during extreme ranges of motion can lead to many common shoulder injuries. [Note: Horrigan also discussed shoulder instability in the November ’95 and April ’96 Sportsmedicine columns; both are available at]

The shoulder is surrounded by ligaments, which attach bone to bone. The ligaments are actually connected and form the joint capsule. Think of the joint capsule as an organic Saran Wrap. Two shoulder movements make the ball move forward in the socket: the throwing motion and a pushup or bench-press movement. The front of the capsule becomes overstretched because the ball continually moves forward. Years of bench presses, incline presses, flyes, cable crossovers and pullovers can stretch the capsule too much and cause shoulder pain.

One year ago new research shed light on the process. The shoulder instability caused by an overstretched capsule is usually found in athletes older than 30. When such instability appears in younger athletes, it’s believed to be due to tightness in the back of the capsule and a tear of the cartilage around the bony socket of the shoulder joint.

The tightness of the back capsule lets the ball pivot and rotate too much. A throwing athlete can appear to have too much external rotation and too little internal rotation but actually may not be unstable. The tight posterior capsule will drive the ball upward and can tear the cartilage ring. The problem is known as a SLAP lesion, which stands for the Latin terms that describe the location of the tear’superior labrum anterior posterior. The action may explain why many rotator cuff tears occur on the bottom of the cuff instead of the top from movement against the roof of the shoulder. The torn cartilage ring often creates clicking in the shoulder, which may or may not cause pain.

I’ve written much about the tightness of the shoulder in weight-trained athletes’that they needed to increase their external rotation. That’s still the case for many trainees. Some are tight in both internal and external rotation and should stretch in both directions. Some trainees participated in other sports while growing up (baseball, football, etc.) and have some degree of the problem already. Bench presses, incline presses, behind-the-neck presses, flyes and pullovers increase the problem.

Patients who have SLAP lesions, too much external rotation and limited internal rotation need to stretch the posterior capsule and strengthen the rotator cuff muscles. Often that’s enough to make the shoulder problems manageable. If external rotation is also limited (maybe you can’t do behind-the-neck presses or hold a barbell for squats), then the front capsule and muscles must be stretched too.

Patients who have SLAP lesions often have biceps tendon pain. Biceps tendinitis doesn’t occur by itself. The biceps tendon may be compressed, or impinged, between the ball and the roof, or it may be a symptom of the SLAP lesion. What you need to realize is that half of the biceps’ origin is on the bony socket of the shoulder, and half attaches into the cartilage ring. If the SLAP lesion is torn at the site of biceps tendon attachment, the biceps tendon is often painful.

I’ll describe exercises to help improve that situation in the next issue of IRON MAN.

Editor’s note: Visit for reprints of Horrigan’s past Sportsmedicine columns that have appeared in IRON MAN. You can order the book Strength, Conditioning and Injury Prevention for Hockey by Joseph Horrigan, D.C., and E.J. ‘Doc’ Kreis, D.A., from Home Gym Warehouse, (800) 447-0008 or at

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