What Are the Most Common Shoulder Injuries?

Common shoulder injuries include shoulder sprain, strain, tear, bone fracture, impingement, and frozen shoulder.

A shoulder injury is an injury to any of the structures in the shoulder joint, including bones, muscles, tendons, ligaments, and cartilages. Shoulders are easily injured because they have a complex structure that provides a wide range of motion. They are the most mobile joints in the body and consequently, the most unstable.

Each shoulder is composed of three bones, the collarbone (clavicle), the shoulder blade (scapula), and the upper arm bone (humerus). The bones are held in place by ligaments, attached to the muscles by tendons, and lined with cartilage to prevent friction between the bones. Fluid-filled sacs, known as bursae, cushion and lubricate the joints, enabling them to glide smoothly.

There are four joints in the shoulder with several muscles, ligaments, and tendons anchoring them, and any of these can get injured. The four joints are:

Sternoclavicular joint: The joint where the clavicle is attached to the upper part of the breastbone (sternum).

Acromioclavicular joint: The joint where the clavicle is attached to a projection in the shoulder blade known as the acromion.

Scapulothoracic joint: Not a true joint but the region where the scapula glides over the thoracic rib cage.

Glenohumeral joint: A highly mobile ball and socket joint in which the head of the humerus forms a ball that fits into a socket (glenoid) in the scapula. The socket is shallow and the ball is larger than the socket, which factors allow maximum movement.

Common shoulder injuries include the following:

Shoulder sprain

A shoulder sprain is an acromioclavicular joint (AC joint) injury. The ligaments stabilizing this joint are stretched or partially torn in a low-grade injury and fully torn in a severe injury. A severe injury to the AC joint ligaments can lead to:

• Dislocation: The collarbone gets dislocated and appears as a bump on the shoulder. 
• Separation: The collarbone separates from the acromion, and the muscles detach from the collarbone.

Shoulder strain

A shoulder strain is an injury when a muscle or tendon in the shoulder gets stretched or torn. This can occur with overuse or when the shoulder remains in one position for a long time.

Shoulder tear

A shoulder tear is an injury to soft tissue such as muscles and tendons which give the joint the range of motion. Shoulder tears are caused by:

• Shoulder subluxation: The humerus gets partially dislodged from the glenoid.
• Shoulder dislocation: The humerus gets fully dislodged from the glenoid.

Shoulder tears can be any of the following:

• Rotator cuff tear: Rotator cuff tear occurs in the group of tendons and muscles that connect the upper arm to the scapula. Rotator cuff muscles stabilize the shoulder and allow the arm to rotate and move in many directions.
• Biceps tendon tear: Biceps tendon tear is a tear in the tendons that connect the biceps muscles to the shoulder.
• Labral tear: Labral tear is a tear in the cartilage known as the labrum which lines the shoulder socket. Labral tears may be:
  • Superior labrum anterior and posterior (SLAP): Labral tear in the top part of the socket.
  • Bankart tear: Labral tear in the bottom part of the socket.

Other shoulder injuries include:

• Bone fracture: Break in the shoulder bones 
• Shoulder impingement: The acromion puts pressure on the soft tissues beneath when the arm is lifted away from the body. It can cause bursitis and tendinitis.
• Frozen shoulder: Stiffness and pain that limits movement, caused by abnormal bands of tissue (adhesions) from old injuries.

The symptoms of shoulder injury include the following:

• Stiff and painful shoulder
• Swelling and bruising
• Inability to rotate the arm in all the normal positions
• A feeling as if the shoulder may slide out of the socket
• Lack of strength to lift or perform daily activities with the shoulder

The main causes of shoulder pain include the following:

• A traumatic injury from a fall with impact on the shoulder, or a blow to the shoulder, such as from an accident
• Overuse of the shoulder in excessive overhead motion in sports such as swimming, daily activities that involve excessive repetitive motion, or poor posture while typing
• Wearing out of cartilage with age (osteoarthritis)
• Inflammation of the bursae (bursitis) or tendons (tendinitis)
• Conditions such as rheumatoid arthritis
• Bone spurs in the joint

Shoulder pain may also result from:

• Radiating pain from a pinched nerve in the neck
• Heart attack
• Referred pain from problems in another organ such as gallbladder or liver

The first treatment for minor injuries is to avoid movements that cause pain and RICE (rest, ice, compression, and elevation). Other treatments include:

• Medications for pain and inflammation
• Physical therapy and exercises
• Surgery in severe injuries

Soft tissues usually take a fairly long period to heal. Severe shoulder injuries can take six months or more to heal and sometimes may never completely heal. Cartilage tears in particular take a long time because they have no blood supply.