An acromioclavicular or “AC joint” injury refers to damage to the joint between the end of your collarbone (clavicle) and the upper part of your shoulder blade (acromion). Depending on which anatomical structures, there are different types of severity (Ahillen, Braman and Tompkins, 2015). Classification by Rockwood I-IV, going from sprain to complete displacement.
The AC joint is the link between shoulder blade and clavicle; the two bones are covered by a relatively thin capsule, being enforced by strong ligaments anteriorly and posteriorly.
The AC joint is usually injured following an impact to the point of the shoulder. The impact may be with a stationary object, such as the ground or wall, or with a moving object, such as an opponent. This impact can push the upper part of the shoulder blade beneath the end of the collarbone, causing a tear to the ligaments which support the joint.
Management initially should be to follow the “RICE regime” and seek advice from a Physiotherapist to help stabilise the joint. Strengthening of the shoulder after injury is required and bracing, taping and padding may help an earlier return to sport. Significant disruption to the ligaments which displaces the shoulder blade or clavicle may require surgical stabilisation.
Ahillen E.J., Braman J.P. and Tompkins M., 2015, Disorder of the AC Joint and Suprascapular Nerve Compression Syndrome, Springer, New York, US, p: 233