The acromioclavicular joint, or ACJ, is formed by the end of the clavicle (collar bone) and the acromion (part of the shoulder blade).
There are ligaments that keep this joint stable and a small disc between the ends of the bones which can degenerate by our fifth decade of life. Muscles including the deltoid and trapezius that attach to the clavicle also aid stability.
Injury to the clavicle
Acromioclavicular pain can be caused by a number of different problems;
- Osteoarthritis is common in the joint from the age of 40 and meniscal injury can occur due to injury of the small meniscal disc that sits between the acromion and clavicle.
- Clavicle fractures usually occur by a direct blow to the shoulder such as a rugby tackle, trauma or a fall onto the acromion.The middle third of the clavicle is the most prone to injury as it is thin and weak. Fractures are classified into three types and are treated accordingly (Neer’s).
- Instability can occur by way of dislocation or subluxation. This occurs by taking impact onto the shoulder directly, such as slipping over without having the chance to put your arm out to break your fall. The degree of separation of the two bone ends help to define the classification of injury – Rockwood’s classification.
What will you feel?
Pain is often felt over the ACJ and it can be very painful lying on the arm at night. Activities that involve lifting the arms overhead, front crawl swimming and reaching across the body are often painful.
What does treatment involve?
Treatment starts with activity modification, rest, painkillers and anti-inflammatory drugs. Physiotherapy can be of benefit to improve shoulder mobility, release tight and sore muscles and ensure the shoulder is strong. If all that fails then cortisone injection into the AC joint can be very effective.
Surgery may be considered in some cases depending on the severity of the injury. A shoulder consultant will guide you through this if all conservative treatments have failed.
Ensuring the shoulder has normal range of motion (ROM) is vital. Manual therapies can help restore movement in the shoulder joint, the ACJ and the thoracic spine (upper back). This might involve massage, joint mobilisation, trigger point release, acupuncture and/ or exercise.
Exercises will be guided by your physiotherapist to avoid aggravating the injury and will include strengthening the shoulder joints and the trunk. Some of the exercises you will be taught might be included in the below videos.