A shoulder sprain is a tear of shoulder ligaments, the tough bands of fibrous tissue that connect bones to one another inside or around the shoulder joint. Although most people think of the shoulder as a single joint between the upper arm bone (humerus) and the torso, the shoulder actually has several smaller joints outside the arm bone's socket. Ligaments connect the four bones that are important to the shoulder's function. These bones include:
A sprain that tears ligaments in the shoulder most often occurs at the joint between the acromion and collarbone, called the acromioclavicular joint. This injury sometimes is called a shoulder separation. Less often, a shoulder sprain involves the joint between the breastbone and collarbone, called the sternoclavicular joint. This joint is within an inch of the midline of the chest. Many people would not guess that it's part of the shoulder.
Acromioclavicular Joint Sprain
The acromioclavicular joint is supported by the acromioclavicular ligament and the coracoclavicular ligament at the outside end of the collarbone near the shoulder. They bind the shoulder blade and collarbone tightly together. It takes a lot of force to tear these ligaments. The most common causes of this type of shoulder sprain are either a strong, direct blow to the front or top part of the shoulder or trauma from a fall, especially during athletic training or competition. A shoulder sprain also can be caused when a person collides with an object, such as a goal post or a tree (when skiing). Shoulder sprains are common among athletes who participate in high-velocity or contact sports such as alpine skiing, jet skiing, football, rugby and wrestling.
Depending on the severity of the ligament damage, acromioclavicular sprains usually are classified into three grades:
Some doctors classify the most severe acromioclavicular injuries into even higher grades or types, from IV to VI. With each higher grade, the collarbone is more displaced away from its normal position and the shoulder is more severely deformed.
Sternoclavicular Joint Sprain
The sternoclavicular joint is located where the inner end of the collarbone meets the breastbone. Because the sternoclavicular joint is even more tightly connected than the acromioclavicular joint, sternoclavicular injuries occur very rarely, only about one-fourth as often as acromioclavicular injuries. When the sternoclavicular joint is sprained, it is often when a driver's chest strikes the steering wheel during an auto accident, or when a person is crushed by an object. In athletes, sternoclavicular sprains sometimes are seen among football players and rugby players after a direct kick to the breastbone or some sideways tackles that impacts the back or side of the shoulder.
Sternoclavicular sprains are graded from I to III:
If you have a Grade I acromioclavicular sprain, you will have slight swelling and tenderness at the outside tip of your collarbone. You will have mild pain when you move your arm or shrug your shoulder. In more severe acromioclavicular joint sprains, swelling will distort the normal contour of your joint, and the area will be very tender. You will feel significant pain when you try to move your arm or when your doctor or athletic trainer touches the joint while examining it.
Symptoms of sternoclavicular sprains are similar to those of acromioclavicular sprains, except swelling and tenderness are located near the midline of the chest.
The doctor will inspect both your shoulders, comparing your injured shoulder with your uninjured one. The doctor will note any swelling, shape differences, abrasions or bruising and will check for extra motion in the acromioclavicular and sternoclavicular joints. He or she will test your ability to move your shoulder, and will ask about arm pain. Your doctor will gently press and feel your acromioclavicular joint, sternoclavicular joint and collarbone.
Because many important blood vessels and nerves travel through your shoulder area, the doctor will also check the pulses at your wrist and elbow and will check the muscle strength and skin feeling in your arm, hand and fingers.
If your physical examination suggests that you have a severe shoulder sprain or fractured bone in the shoulder area, your doctor will order x-rays. In more severe acromioclavicular joint injuries, your doctor may also order magnetic resonance imaging (MRI) scans or computed tomography (CT) scans.
If you have a Grade I shoulder sprain, your discomfort should ease within one to two weeks, and you will be able to resume normal activities as soon as you can move your shoulder through its normal range of motion without pain. If you have a Grade II sprain, your discomfort should lessen within two weeks, but it may take as long as six to eight weeks before you can return to your usual athletic activities. People with Grade III shoulder sprains often return to work within four weeks. Athletes who participate in contact sports, however, have a high risk of injuring the area again, so they often need three to five months of rehabilitation before returning to their sport.
Wearing protective padding during high impact sports might offer some protection against sprains and other shoulder injuries. If you have had a sprained shoulder, you may help to prevent injuring it again by practicing shoulder strengthening exercises recommended by your doctor or physical therapist.
Treatment depends on the type of sprain and its grade.
Call your doctor if a fall or blow to your shoulder makes the area painful, swollen, tender or deformed.
The outlook depends on the type of sprain and its grade:
National Institute of Arthritis and Musculoskeletal and Skin Diseases
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American Orthopaedic Society for Sports Medicine
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