What is the AC joint?
AC joint injury is a common sports injury that we see at Movement Centre. The AC joint (acromio-clavicular joint) is a small joint at the top of the shoulder. It is where the clavicle (collar bone) connects to the top of the scapular (shoulder blade). AC joint injuries can generally be grouped into acute or chronic categories.
How and why do injuries occur?
Acute injuries of the AC joint generally occur from impact to the top of the shoulder. Some of the most common mechanisms for this include:
- Tackling in rugby/league
- Falling on the shoulder – particularly when landing on the shoulder itself
- Fall off bike
- Shoulder contact to wall – as in ice-hockey or indoor sports
Chronic injury and irritation of the AC joint can result from a poorly managed acute injury. Most commonly however, chronic injury is a degeneration of the joint itself. This can develop into a condition called AC joint osteolysis. This can occur in response to altered biomechanics resulting from overuse – often in pressing movements ie. bench pressing.
Acute shoulder injuries involving the ACJ
A hard tackle with impact into the shoulder, or a fall onto the shoulder is usually the mechanism of injury. Patients who experience this injury often describe it as one of the most uncomfortable and unsettling pains they have felt. Injury to the AC joint involves stretching or tearing the ligaments that support the joint. The Grade of the AC joint injury depends on the severity of the stretching/ tearing.Grading of the injury
There are several ways of grading acute injuries of the AC joint. The most common is a Grading of 1-3, as follows:
- 1. Partial damage to the joint capsule and stretching of the AC ligament
- 2. Damage to the AC ligament and involvement of the coracoclavicular ligament
- 3. Rupture of both AC ligament and the coracoclavicular ligament
Grade 1-3 generally all result in a “step” deformity – in which there is a palpable and visible step at the AC joint.
Acute AC joint physio management
Immediate AC joint injury physio will work to assess the severity of the injury and whether any other structures are involved. It is important to rule out collar bone fractures, rotator cuff damage and bursal inflammation. In severe cases, X-ray and orthopaedic referral may be necessary.
Physio in the early stages of acute injury is focused on protecting the joint from further injury, managing pain and swelling, and maintaining the health and mobility of the surrounding tissue. Light exercise and strengthening of the scapular stabilisers and rotator cuff muscles can generally be commenced within pain tolerances – as advised by your doctor or physio.
Return to sportReturn to sport varies greatly depending on the individual, the injury and the sport. Rest from pressing exercises, overhead lifting, and further impact is generally required for 1-3 weeks for grade 1 sprains, and up to 8-12 weeks or more for Grade 3. In this time, mobility work for the shoulder, scapula and neck are vital to minimise ongoing movement restrictions. Our physios at Movement Centre in Randwick love working with their patients to ensure they have the range, strength and function to make a safe and lasting return to the activities they love.
Chronic injuries involving the acromio-clavicular joint
Osteolysis of the AC joint can be a tricky condition to manage. It often results from repetitive loading through the AC joint in movements like chest/ bench pressing and over-head pressing. Early management often focuses on a relative reduction in pressing load, and a focus on strengthening the muscles of the upper back. We tend to encourage our patients to work with a 3:1 ratio of pulling: pushing exercises in their weight training.
If this doesn’t work, then a short rest from chest work may be necessary. While resting these injuries, our physios focus on strengthening the upper back, improving scapular mobility, thoracic spine mobility, and opening up through the chest.
For long-term problems that don’t resolve with activity modification and relative rest, orthopaedic consultation may be necessary. Surgery to debride the joint and clean up the degenerative tissue is a last resort but can provide great relief and a return to most activities.
If you are experiencing ongoing AC joint pain, or have an acute AC joint injury, come and see our physios at the Movement Centre. We are experts in diagnosing the problem, and giving you strategies to get back to the activities you love.