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Patient education: Acromioclavicular joint injury (shoulder separation) (Beyond the Basics)

Scott M Koehler, MD
Section Editor
Karl B Fields, MD
Deputy Editor
Jonathan Grayzel, MD, FAAEM
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The acromioclavicular (AC) joint is formed by the cap of the shoulder (acromion) and the collar bone (clavicle). It is held together by strong ligaments (figure 1). The outer end of the clavicle is held in alignment with the acromion by the acromioclavicular ligaments and the coracoclavicular (CC) ligaments.

The AC joint is strong, but its location makes it vulnerable to injury from trauma. Injury to the ligaments (also called shoulder separation) can occur as a result of a fall, direct blow, or other trauma.


Acromioclavicular injury — Acromioclavicular injury is labeled as a type I, II, III, IV, V, or VI, depending upon the extent of injury and number of ligaments involved. The type of injury can usually be determined with a physical examination and x-rays.

Type I injuries involve a sprain or partial tear of AC ligaments with no injury to the CC ligaments. This causes a tender AC joint that often has mild swelling. Type I sprains usually heal within a few weeks.

Type II injuries involve a complete tear of the AC ligaments and a sprain or partial tear of the coracoclavicular (CC) ligaments. This causes a tender AC joint, often with significant swelling (figure 2).

Type III injuries involve a complete tear of both the AC and CC ligaments (figure 3). The AC joint will appear abnormal, although swelling may obscure the degree of injury. People with type III injuries have significant tenderness of the CC ligaments, which helps distinguish type III from type II injuries. Type III injuries often take longer to heal (several weeks to months).

Type IV, V, VI injuries are the most severe. Treatment often requires surgery.

Other causes of shoulder pain — Arthritis of the shoulder joint is a common cause of shoulder pain. Arthritis can occur after AC separation or as a natural part of the aging process. (See "Patient education: Shoulder osteoarthritis treatment (Beyond the Basics)".)

Other possible causes of shoulder pain include rotator cuff tendonitis or tears, scapulothoracic bursitis, biceps tendonitis, frozen shoulder (also called adhesive capsulitis), and others. (See "Patient education: Rotator cuff tendinitis and tear (Beyond the Basics)" and "Patient education: Biceps tendinitis or tendinopathy (Beyond the Basics)" and "Patient education: Bursitis (Beyond the Basics)" and "Patient education: Frozen shoulder (Beyond the Basics)".)


Pain relief — Ice can help reduce pain from AC joint injuries, as the joint is close to the skin. If needed, a non-prescription pain medication such as acetaminophen (Tylenol), ibuprofen (eg, Advil, Motrin), or naproxen (eg, Aleve) can be taken (see "Patient education: Nonsteroidal antiinflammatory drugs (NSAIDs) (Beyond the Basics)"). No more than 3000 mg of acetaminophen is recommended per day. Anyone with liver disease or who drinks alcohol regularly should speak with his or her health care provider before taking acetaminophen.

Type 1 — Type I injuries are best treated initially with rest, ice, and protection, often with an arm sling. Ice can be applied for 15 minutes every four to six hours as needed. Rest includes avoiding overhead reaching, reaching across the chest, lifting, leaning on the elbows, and sleeping directly on the shoulder.

Range-of-motion exercises are recommended as soon as they can be tolerated.

Range-of-motion exercises — Range-of-motion exercises are recommended early in the recovery period. These exercises are intended to help maintain joint mobility and flexibility of the muscles and tendons in the shoulder. Pain should not exceed mild levels with any range-of-motion/flexibility exercise. Anyone who feels sharp or tearing pain while stretching should stop exercising immediately and consult with a healthcare provider.

Weighted pendulum stretch – The weighted pendulum stretching exercise performs two functions:

Gently stretches the space in which the tendons pass to relieve pressure on the tendons

Prevents the development of a frozen (stiff) shoulder

This exercise can be started almost immediately after a shoulder injury. This exercise should be performed for five minutes once or twice per day. The exercise is performed as follows (figure 4):

Relax your shoulder muscles

While standing or sitting, keep your arm vertical and close to your body (bending over too far may pinch the rotator cuff tendons)

Allow your arm to swing forward to back, then side to side, then in small circles in each direction (no greater than 1 foot in any direction). Only minimal pain should be felt.

Stretch the arm only (without added weight) for three to seven days. The difficulty of this exercise can be increased by adding 1 to 2 pounds (0.5 to 1 kg) each week and gradually increasing the diameter of the movements (not to exceed 18 to 24 inches or 45 to 60 cm)

After a few weeks this exercise should be supplemented or replaced by other exercises to target specific areas of tightness/restriction. The pendulum stretch may be recommended as a warm up for more localized flexibility exercises and/or strengthening exercises.

When performed correctly the pendulum exercise should not result in more than mild discomfort. If more pain is felt, consult a healthcare provider for instructions.

Return to activity — Most people are able to return to full activities between three days and two weeks after a type I acromioclavicular joint injury. Athletes who use overhand motions (eg, those who play tennis and serve volleyball, baseball pitchers, American football quarterbacks) may require two to three weeks to return to full activity. Complete healing may take four to six weeks. Type I injuries generally heal well without an increased risk of reinjury.

Type II — Type II injuries usually cause greater pain and swelling than type I injuries. Initial treatment may include rest, ice, pain medication, and three to seven days of shoulder immobilization in a sling. Range-of-motion exercises and stretching exercises can be started when tolerable. (See 'Range-of-motion exercises' above.)

Strengthening exercises — Muscle strengthening exercises are necessary to improve shoulder muscle strength and help to prevent further injury. These exercises can often be started approximately one to two weeks after beginning the pendulum stretch exercises (described above), depending upon the level of pain.

As pain improves, the level of difficulty of these exercises should be increased. Increased difficulty is necessary to improve muscle strength to a degree that reduces the risk of re-injury. Mild soreness is expected with these exercises, although pain should not continue for more than 24 hours. Sharp or severe pain during or after exercising may indicate a flare of the underlying problem; stop these exercises for a few days if this occurs.

Preparing for strengthening exercises – Once the swelling has decreased, the shoulder may be warmed with cardiovascular exercise or a warm pack and stretched with range-of-motion exercises before beginning strengthening exercises. (See 'Range-of-motion exercises' above.)

Rest after stretching for two or three minutes, then perform 15 to 20 repetitions of each exercise slowly, holding for one to two seconds during each exercise. Flexible rubber tubing, a bungee cord, or a large rubber band can be used for each exercise.

Scapular squeezes – Lie on your back with your knees bent and feet flat. Your arms should be straight out, 6 to 12 inches (15 to 30 cm) away from the side of your body, with palms facing upward. Keeping your low back flat against the ground, squeeze your shoulder blades downward and towards each other, towards the spine (picture 1). Make a conscious effort not to shrug your shoulders and keep the neck relaxed. You should feel the lower muscles between your shoulder blades contracting. Hold for five seconds and repeat 20 times. Do this exercise two to three times per day.

The difficulty can be increased by performing it while sitting and then by holding a piece of tubing in each hand and pulling the hands apart while squeezing the shoulder blades, as described above.

Outward rotation exercise – Hold your elbows at 90 degrees, close to your sides; holding a towel between your torso and the inside of your elbow will cue you to keep your elbow by your side. Hold one end of a rubber band in each hand and rotate the affected lower arm outward 2 or 3 inches, holding for five seconds (picture 2).

Perform the exercise through all available pain-free ranges of motion. Keep the shoulder blades squeezed down and back while performing this exercise.

Return to activities — After a type II AC injury, most people are able to return to full activities when full range of motion and strength are regained, usually after two to four weeks. Complete healing generally requires several more weeks.

Type III — The majority of people with type III injuries can be managed with non-surgical treatment, including rest, ice, immobilization with a sling, and pain medication. A sling may be recommended for three to four weeks to aid in healing and to relieve pain. Treatment follows the same basic protocol for a type II injury, but with a slower progression.

Range-of-motion and strengthening exercises can begin as soon as they are tolerable (see 'Range-of-motion exercises' above and 'Strengthening exercises' above). The intensity of these exercises should be increased gradually, based upon pain.

Return to activities — Patients with a type III injury may return to normal activities between six and twelve weeks following injury, when full range of motion and strength are regained. Some people return to activity sooner or later, depending upon the demands of the specific activity.

Type IV, V, VI — Type IV, V, and VI AC injuries are the most severe. People who have this type of injury should see a physician who specializes in bones and joints (an orthopedist). If nerves or muscles are compressed as a result of the injury, treatment is needed urgently to reduce the risk of long-term complications. Surgery is often recommended.


Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Separated shoulder (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Shoulder osteoarthritis treatment (Beyond the Basics)
Patient education: Rotator cuff tendinitis and tear (Beyond the Basics)
Patient education: Biceps tendinitis or tendinopathy (Beyond the Basics)
Patient education: Bursitis (Beyond the Basics)
Patient education: Frozen shoulder (Beyond the Basics)
Patient education: Nonsteroidal antiinflammatory drugs (NSAIDs) (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Acromioclavicular joint injuries ("separated" shoulder)
Evaluation of the patient with shoulder complaints

The following organizations also provide reliable health information.

National Library of Medicine


American Academy of Orthopaedic Surgeons


National Institute of Arthritis and Musculoskeletal and Skin Disease


American Physical Therapy Association


Arthritis Foundation



Literature review current through: Nov 2017. | This topic last updated: Tue Apr 25 00:00:00 GMT 2017.
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