Most shoulder problems involve the soft tissues, muscles, ligaments, and tendons, rather than the bones.
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The shoulder has more range of motion than any other joint. However, this flexibility also makes the shoulder prone to dislocation and instability. Trauma or overuse can cause tearing or stretching of the soft tissues of the shoulder, so that they can no longer support the joints properly.
The shoulder is made of up of three bones: the upper arm bone, the shoulder blade (scapula), and the collarbone (clavicle).
There are two joints that join the bones of the shoulder. The acromioclavicular, or AC joint, is located where the collarbone meets the tip of the shoulder bone. The glenohumeral joint is where the ball of the upper bone of the arm fits into a saucer-shaped socket in the scapula. A circle of ligaments, tendons, muscles, and cartilage form a stabilizing capsule around that joint; and a sac-like membrane called the bursa helps lubricate the motion between the structures of the rotator cuff and shoulder blade.
Several types of injuries and conditions can affect the shoulder. Most shoulder problems fall into three categories: tendonitis/bursitis, arthritis, and injury/instability.
- Tendonitis–Splitting, tearing, or wear and tear of a tendon, one of the cords that connects muscle to bone, caused by overuse, degenerative disease, repetitive wear and tear from age, or acute injury.
- Bursitis–The inflammation and swelling of one of the fluid-filled sacs located around the joints, caused by excessive use of the shoulder.
- Arthritis–A group of conditions associated with wear and tear, inflammation of the joint, swelling, pain, limited motion, and stiffness. Arthritis may be related to injuries, but is not always.
- Injury/Instability–When a bone in one of the shoulder joints moves or is forced out of its normal position. Instability can result in dislocation of one of the joints of the shoulder.
Common shoulder injuries include:
- Broken Collarbone–The collarbone (clavicle) helps connect the arm to the body. When a break occurs, you may notice a bump over the fracture site, a grinding sensation when you try to raise your arm, an inability to lift your arm because of pain, and/or your shoulder sagging down and forward.
- Burners and Stingers–Named for the burning or stinging pain from the shoulder to the hand, this is a common injury in contact sports. When nerves are injured in a collision, you may experience an electric, warm sensation down the arm, which may be followed by weakness or numbness. Symptoms usually resolve quickly.
- Dislocated Shoulder–When the head of the upper arm bone (humerus) is partially or completely out of the socket, you will experience pain and unsteadiness in your shoulder. You may also experience muscle spasms, swelling, bruising, numbness, and weakness. The shoulder joint can dislocate forward, backward, or downward. Once the shoulder joint is back in place, the severe pain subsides quickly.
- Erb's Palsy–This condition affects one or two of every 1,000 babies. During a difficult delivery, one side of the baby's neck can be stretched, causing nerve damage. The result is a lack of movement in the affected arm. Most newborns recover without surgery.
Fracture of the Head of the Arm Bone–This injury is a common result of falls on an outstretched arm, especially in older adults with osteoporosis.
- Fracture of the Shoulder Blade–High-energy, blunt trauma (such as a crash or a fall from a height) can fracture the scapula. Symptoms include extreme pain when the arm is moved, swelling of the back of the shoulder, and skin abrasions.
- Frozen Shoulder–This disorder is characterized by pain and loss of motion or stiffness in the shoulder. It may be a result of injury or immobilization, and occurs when the capsule surrounding the shoulder joint thickens and contracts. It is most common in women between 40 and 70 years old.
- Impingement–A common cause of pain in young athletes and middle-aged people, this condition results from pressure on the rotator cuff from part of the shoulder blade as the arm is lifted. As the arm is lifted, the front edge of the shoulder blade rubs on the surface of the rotator cuff. You may notice swelling and tenderness in the front of the shoulder, and pain and stiffness when you lift or lower your arm.
- Rotator Cuff Tear–The rotator cuff is a group of four muscles that join the scapula (wing bone of the shoulder) to the top of the arm bone (humerus) and help to lift and rotate the arm and stabilize the ball of the shoulder in the joint. A tear may result from an injury or could be caused by chronic wear. Symptoms can include pain the front of the shoulder and down the side of the arm, loss of motion, stiffness, and weakness of the arm.
- Rupture of the Biceps Tendon–Tendons attach muscle to bone. The biceps tendon attaches the biceps muscle of the upper arm to the shoulder in two places at the top of the arm. If the tendon tears, partially or completely, you may lose some strength in your arm and be unable to turn your arm from palm down to palm up. Symptoms include a sudden, sharp pain in the upper arm, a bulge in the upper arm above the elbow and a dent close to the shoulder, bruising from the middle of the upper arm down toward the elbow, pain or tenderness at the shoulder, and possibly an audible snap.
- Shoulder Joint Tear–A soft, fibrous tissue rim called the labrum surrounds the socket to help stabilize the shoulder joint. The labrum also serves as an attachment site for several ligaments. Injuries to the tissue rim can occur from acute trauma, such as a fall, blow, sudden pull, or violent reach; or from repetitive shoulder motion, such as throwing or weightlifting. Symptoms are very similar to those of other shoulder injuries, and include pain, a sense of shoulder instability, decreased range of motion, loss of strength, and catching, locking, popping or grinding.
- Shoulder Separation–This is an injury of the AC joint, where the collarbone (clavicle) meets the wingbone (acromion). Shoulder separation most commonly results from a fall directly on the shoulder, which sprains or tears the ligaments that surround and stabilize the AC joint and may put the collarbone out of position.
Source: American Association of Orthopaedic Surgeons