Acromioclavicular (AC) Joint Separation

The shoulder is the most mobile joint in the human body with a complex arrangement of structures working together to provide the necessary movement. The shoulder is a ball-and-socket joint made up by the humerus (the ball) and the glenoid (the socket). A strong network of soft tissues, muscles, and bones work cohesively to provide movement and stability to the shoulder. The head of the humerus fits into a shallow socket in the scapula, called the glenoid fossa, while the shoulder capsule, a strong connective tissue, surrounds the shoulder joint. Synovial fluid lubricates the joint and the shoulder capsule to ease the movement of the shoulder.


The acromioclavicular joint, often referred to as the AC joint, is where the clavicle (collarbone) meets the highest point of the scapula (shoulder blade) which is called the acromion. There are ligaments, which are tough bands of tissue, which hold the clavicle and the scapula together and help stabilize the joint by restricting excessive movement. An AC separation, also known as a shoulder separation, is an injury to the ligaments holding your AC joint together. An AC separation is a common injury among athletes and active individuals participating in contact sports such as football and hockey, but can happen to anyone who falls and lands on the tip of their shoulder or elbow. AC separations are often confused with shoulder dislocations, which involve the separation of the glenohumeral joint as opposed to the AC joint.


Individuals who are experiencing an AC separation have the following signs and symptoms:

  • Pain in the shoulder often associated with shoulder or arm weakness
  • Bruising or swelling around the AC joint
  • Limited or restricted range of motion in the shoulder joint
  • A visible bump on the top of the shoulder

If the pain and tenderness near the end of the clavicle persist, a visit to a physician is highly recommended to rule out other conditions or avoid further damage.


An AC separation can typically be identified during a physical examination, especially if it has caused a deformity. The physician will examine the shoulder to test the range of motion of the shoulder joint. When there is less or no visible deformity, the location of the pain as well as X-rays help the physician make the diagnosis. Even mild AC joint injuries can be extremely painful and x-rays may appear normal. However, they can help diagnose the extent of the injury and are also important in ruling out a fracture at the end of the clavicle. An AC separation is typically classified into six grades with the first three being the most common and the last three being less common:

Grade 1: Mild Separation - A mild shoulder separation involves a sprain of the AC ligament which does not move the clavicle and looks completely normal on X-rays.

Grade 2: Moderate Separation - A moderate shoulder separation involves a tear of the AC ligament or partial tear of the coracoclavicular (CC) ligament which moves the clavicle out of alignment to some extent.

Grade 3: Severe Separation - A severe shoulder separation involves complete tears of both the AC and CC ligaments and moves the clavicle noticeably out of alignment.

Grades 4-6 - These injuries cause a significant degree of instability and movement through the AC joint and may require surgical stabilization.


Treatment of an AC separation depends on the grade of the injury and the extent of pain the individual is experiencing. Most AC separations are treated non-operatively and the individual is able to return to all sports and activities with a fully functional shoulder, although a bump may be present.

Rest - It is advised to decrease or completely stop the activity that makes the pain worse. A great way to stay active while allowing the symptoms to subside is to switch to low-impact, cross-training activities such as biking or elliptical machine.

Ice - Placing ice (with a barrier such as a towel) on the most painful areas of the shoulder for up to 30 minutes (less if the skin becomes numb), three to four times a day can greatly soothe the pain and keep the swelling down during the first 48 hours.

Medication - Over-the-counter anti-inflammatory medication such as ibuprofen and naproxen usually help reduce pain and swelling.

Physical Therapy - Physical Therapists will often prescribe specific strengthening and range of motion exercises that promote healing and help recover as much mobility in the shoulder joint as possible. It is crucial that these exercises be done accurately and routinely to optimize recovery of the mobility of the shoulder joint. The physician may require you to wear a sling for a few days until the pain subsides.

Surgery - If conservative treatments and other procedures have not helped reduce symptoms, the physician may recommend surgery to reduce pain or restore function and stability.

  • Distal Clavicle Resection - After an AC joint injury, some patients will develop damage to the cartilage in the AC joint causing continued pain. The physician may recommend a minimally-invasive arthroscopic procedure called distal clavicle resection or excision to help relieve pain and restore range of motion. Small incisions are made around the joint where surgical instruments and the scope, which is essentially a small camera, will go into these incisions and the image will be sent to a video monitor allowing the physician to see inside the joint. Using special surgical instruments, the physician will remove a small portion of the end of the clavicle, preventing the damaged, arthritic surfaces from rubbing against one another and causing pain. Sutures will be used to close the incisions and the arm will be placed inside a sling for five to seven days until the incisions have healed.
  • AC Joint Reconstruction - If the diagnosed pain is a result of AC joint instability, the physician may recommend a reconstructive procedure to improve stability and restore function. An AC joint reconstruction involves repair of the torn or stretched ligaments so that they are better able to hold the AC joint in place. This procedure may utilize arthroscopy (a small camera to see inside the shoulder) to assist, but depending on the severity of the condition, some patients may require an open surgery which involves a larger incision over the shoulder to perform repairs. Following the surgery, the arm is kept in a sling for up to six weeks to facilitate healing.


After sustaining an injury to the AC joint, some patients develop persistent pain related to osteoarthritis, or deterioration of cartilage, of the AC joint. Regardless of the treatment approach taken, patients go through a rehabilitation program which includes physical therapy exercises that are crucial to restore range of motion. Most individuals heal and return to their previous level of activity within two to three months of non-operative treatment. However, some patients do require surgery. Each patient is unique, so the therapy program will vary based on his/her level of pain, extent of injury, and desired level of activity they would like to return to. Recovery after surgery can take anywhere from six weeks to three months depending on the complexity of the procedure, but the individual's commitment to following all the instructions and guidelines given by the physician and the exercises prescribed by the physical therapist is an important factor in returning to all the desired activities.




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