If the ligaments in the shoulder are loose, the shoulder is said to be “lax”. If this laxity can not be controlled by the rotator cuff, then shoulder becomes “unstable”. In collision sports like football, instability most often is the result of a trauma or blow to the shoulder and the athlete feels like the shoulder comes part way or completely out of joint. In throwers, however, instability is much more subtle. It develops gradually over time from the thousands of throws year after year stretching the ligaments creating increased laxity. If this laxity is too much for the rotator cuff to control, then the shoulder will slip slightly off-center during the throwing motion, causing pain. This can result from increasing laxity or from rotator cuff weakness. The symptoms are pain and loss of velocity, rather than a sensation of “slipping out of place”.
If the cause of this instability is from rotator cuff weakness, strengthening the cuff through rehabilitation will usually solve the problem. If the cause is too much laxity, increasing rotator cuff strength may suffice, but has less of chance of doing so. Because there is no way to tell if the rehabilitation will work beforehand, and surgery to tighten the shoulder has a lengthy recovery, I always try rehabilitation first. The odds are in your favor that it will work, and work quicker than surgery plus rehabilitation would. However, if physical therapy does not succeed, surgery to tighten the ligaments and capsule may be necessary. This can be done arthroscopically as an outpatient.
If the labrum is detached, this needs to be repaired also. This is common in throwers, and involves using suture anchors to attach suture to the bone (glenoid socket), then passing the sutures through the labrum and tying the labrum down to the bone.
After the sutures are tied, the repair needs a chance to heal. The sutures are not strong enough to keep the ligaments permanently tight by themselves, so we depend on the body to heal the repair with living tissue. It takes about six weeks for this tissue to be strong enough for everyday activities, so you would wear a sling for about six weeks after surgery. It takes about three months for the repair to be strong enough for light throwing, so you could begin throwing three months after the surgery at the earliest. Remember, the rotator cuff also controls the shoulder, so the cuff must be strong enough to do its job before you can start throwing after surgery. That is what the physical therapy is for!