Shoulder joints are dislocated when the humerus is forcefully abducted and pulled backward.
Arms have a great deal of flexibility in their movement at the shoulder. They can swing out and in, and even swing in circles. However, this flexibility comes at a cost which is that the shoulder joint is at greater risk of injury than other, less flexible joints.
Rotator cuff tears are the most common conditions affecting the shoulder . The main functions of the cuff are to stabilize the glenohumeral joint and rotate the humerus outward. When shoulder trauma occurs, these functions can be attenuated, suggesting a rotator cuff tear . The tears occur in one or more of the four tendons of the rotator cuff muscles. The tendons of the rotator cuff, not the muscles, are most commonly torn. Of the four tendons, the supraspinatus is most frequently torn as it passes below the acromion. The tear usually occurs at its point of insertion onto the humeral head at the greater tubercule.
Acute tears may occur from falling on the shoulder or while exerting too much force during an overhead motion. These types of traumas elicit sharp, throbbing pain, and limited range of motion. Overuse of the muscles is subject to chronic shoulder conditions, such as arthritis and bone spurs, which can eventually lead to a tear. Once a tear happens in the rotator cuff, it is much more likely to recur. To avoid this, proper strengthening exercises can be performed . Partial tears can be treated with rest, anti-inflammatory drugs, and, eventually, physical therapy. A complete tear usually requires surgical procedures such as arthroscopic repair, open repair, or mini-open repair. These procedures are used in the rotator cuff area to remove bone spurs (subacromial decompression), repair the tear by suturing the tendons, transfer tendons, and even replace the shoulder joint when arthritis has developed.
The shoulder joint is the most frequently dislocated major joint of the body . In a typical case of a dislocated shoulder, a strong force that pulls the shoulder outward (abduction) or extreme rotation of the joint pops the ball of the humerus out of the shoulder socket. Dislocation commonly occurs when there is a backward pull on the arm that either catches the muscles unprepared to resist or overwhelms the muscles. When a shoulder dislocates frequently, the condition is referred to as shoulder instability. The shoulder can dislocate either forward, backward, or downward. Not only does the arm appear out of position when the shoulder dislocates, but the dislocation also produces pain. Muscle spasms may increase the intensity of pain. Swelling, numbness, weakness, and bruising are likely to develop. Problems seen with a dislocated shoulder are tearing of the ligaments or tendons reinforcing the joint capsule and, less commonly, nerve damage. Doctors usually diagnose a dislocation by a physical examination; x-rays may be taken to confirm the diagnosis and to rule out a related fracture.
Doctors treat a dislocation by putting the head of the humerus back into the joint socket (glenoid fossa) of the scapula. This procedure is called manipulation and reduction (M&R). The arm is then immobilized in a sling or a device called a shoulder immobilizer for several days. After pain and swelling have been controlled, the patient enters a rehabilitation program that includes exercises to restore the range of motion of the shoulder and strengthen the muscles to prevent future dislocations. These exercises may progress from simple motion to the use of weights.
After treatment and recovery, a previously dislocated shoulder may remain more susceptible to reinjury, especially in young, active individuals. Ligaments are stretched and may tear due to dislocation. Torn ligaments and other problems resulting from dislocation can increase the chance of repeated dislocation. A shoulder that dislocates severely or often, injuring surrounding tissues or nerves, usually requires surgery to repair the damaged parts of the shoulder.
A separated shoulder occurs where the collarbone (clavicle) meets the shoulder blade (scapula). When ligaments that hold the AC (acromioclavicular) joint together are partially or completely torn, the outer end of the clavicle may slip out of place, preventing it from properly meeting the scapula. Most often the injury is caused by a blow to the shoulder or by falling on an outstretched hand. After injury, it is hard to do a 180 degree rotation.
Shoulder pain or tenderness and, occasionally, a bump in the middle of the top of the shoulder (over the AC joint) are signs that a separation may have occurred. Sometimes the severity of a separation can be detected by taking x-rays while the patient holds a light weight that pulls on the muscles, making a separation more pronounced. A shoulder separation is usually treated conservatively by rest and wearing a sling. Soon after injury, an ice bag may be applied to relieve pain and swelling. After a period of rest, a therapist helps the patient perform exercises that put the shoulder through its range of motion. Most shoulder separations heal within two or three months without further intervention. However, if ligaments are severely torn, surgical repair may be required to hold the clavicle in place.