The acromioclavicular or AC joint is located at the tip of the shoulder where the acromion portion of the shoulder blade (scapula) and collarbone (clavicle) join together. The AC joint is not as mobile as the large main shoulder joint and only moves when the shoulder is overhead or across the chest. The joint is partly filled with a thick pad of cartilage, known as the meniscus; which allows the joint to move. The AC joint is stabilised by its capsule and additional ligaments (coraco-clavicular ligaments). The AC joint can become degenerate or worn (arthritic) over time and become painful. Sometimes, after trauma, the joint may become unstable.
Symptoms of AC Pain
AC joint pain is usually felt at the top of the shoulder overlying the joint itself and can sometimes radiate up the side of the neck. The pain is often worse during activities where the bones either side of the joint are forced together. This includes activities such as reaching overhead, reaching in front of the body across the other shoulder (such as when pulling a seatbelt on), and during activities such as press ups. AC pain is often seen in people who do a lot of repetitive overhead activity. AC pain can occur at any age but in older patients frequently occurs in conjunction with other shoulder problems such as impingement.
Physiotherapy is the most appropriate first line treatment for most AC problems. A combination of exercise and manual therapy may be used to help settle the pain. If physiotherapy alone fails to resolve the issue a steroid injection or Ostenil injection in combination with physiotherapy may be considered. If the pain cannot be adequately controlled with the above measures, surgery may be considered.
Acromioclavicular Joint Dislocations and Instability
The joint is normally stabilised by a number of strong ligaments. These ligaments can be damaged with significant trauma to the shoulder. The commonest mechanism is a fall onto the side of the shoulder. As a result, the AC joint can become unstable and can even dislocate. Injuries to the AC joint are classified in terms of severity from type 1 to type 6. The higher larger the number the more severe the injury.
Acromioclavicular Joint Pain
In types 1 and 2, as well as some type 3 injuries the strongest ligaments remain intact and instability is mild. Such an injury is very likely to settle with physiotherapy. Early physiotherapy will produce the best outcomes in this case. In some type 3 injuries and 4 to 6, the ligament damage and hence resultant instability is more severe. These types of injuries are more likely to need surgical intervention to address the symptoms. The need for surgery should be considered on an individual basis and will depend on a number of factors including symptoms, severity of damage, age, as well as working and recreational/ sporting activities etc. However even when surgery is required, postoperative physiotherapy is crucially important. At YSP we work closely with a number of orthopaedic surgeons across Yorkshire, details of these surgeons can be found here.
Acromioclavicular Joint Osteolysis
AC Joint osteolysis is essentially a stress fracture of the outer end of the clavicle (collarbone), where it joins the acromion to form the AC joint. Osteolysis occurs when bone is eroded faster than it can be replaced or repaired.
Excessive activities that load the outer clavicle and AC joint can lead to osteolysis, as the repetitive damage exceeds the ability for the bone to heal after loading. The AC joint is maximally loaded with heavy overhead activities. AC joint osteolysis can be more common in strength and power athletes, such as weightlifters, power lifters and rugby players. Osteolysis is not restricted to athletes, jobs involving heavy, overhead work, such as builders and plasterers also have higher occurrence of osteolysis at the AC joint.
Treatment for osteolysis may include a period of rest from aggravating activities. At YSP we can help to facilitate return to activity and pain relief with exercises to help strengthen and off load the AC joint. Occasionally a steroid or Ostenil injection may also be used to help settle the symptoms associated with AC joint osteolysis. If all the above fails surgery may be considered.
If you would like help with any aspect of AC joint pain contact YSP here.