The Acromioclavicular Joint (AC) is often a problem area for many individuals, both in athletic and general populations. The AC joint is located at the top of the shoulder formed by the junction between the acromion and the clavicle. This joint is very much responsible for giving us the ability to raise our arms above the head. The AC joint is a gliding synovial joint which is important because by acting like a strut it aids the movement of the scapula leading to a greater range of arm motion. Unlike the glenohumeral joint which has the benefit of being stabilized by a combination of ligaments and muscles (rotator cuff), the AC joint must solely rely upon ligaments to prevent any kind of extraordinary mobility this is due to the fact that there is no muscle that crosses directly over the joint. The AC Joint relies on three ligaments specifically to maintain proper stability within the joint these are the Coracoclavicular ligament, Coracoacromial ligament, and the Acromioclavicular Ligament. To the left is a model picture of the Acromioclavicular Joint. Due to this reliance on ligaments alone to stabilize the joint one can safely assume that it would take very little to cause the joint to become excessively mobile. The most often onset of AC Joint issues is correlated with a traumatic injury involving some kind of high force impact. Occurrences of this nature are most commonly seen in physical contact athletes such as Mixed Martial Artist, Hockey, Football, and Lacrosse. Ligaments are the most elastic tissue in the body and once they have been pulled on by externally applied forces the ligament becomes permanently stretched leading to the increased mobility we observe. More common though and probably more relevant to the general population is the onset of AC Joint issues in a gradual manner. In general this onset slowly develops as an individual loses scapular stability in addition to experiencing shortness in the pectoral muscle primarily the minor pec this leads to an anteriorly tilted scapula that is slightly winged out. This dysfunction leads to some major issues between the acromion and the clavicle most commonly presenting in increased separation between the two. Individuals suffering from AC Joint pain may also be lacking in thoracic mobility causing them to compensate and gain back their lack of ROM by overusing the scapula.
When trying to correct such issues you must take into account all possible dysfunction and focus on slowing improving upon each issue. It is not relevant though what has brought about the issues it is only important that you focus your attention on improving scapular stability, increasing lower trapezius strength and anterior serratus strength in order to pull the acromion back in working order with the clavicle. One should also employ foam rolling and stretching in the pectoral muscles to decrease anterior forces.
Now that we have discuss what the AC Joint is, what are some of the dysfunction and causes of this joint, and how they should be addressed it is time to offer some considerations to be taken into account when training to train around such an injury. Typically there are a lot of variable factors to be taken into account when training an individual with AC dysfunction, but three good rules I’d start with is avoid adduction of the arm especially in a horizontal path, do not apply any kind of direct contact or force onto the joint as most individuals experience pain to the touch, and lastly avoid any kind of full extension with the humerus. These are simple guidelines one can use to train around issues involving the acromioclavicular joint.
Well now that you have had your crash course in AC Joint dysfunctions and possible ways to both improve them and train around them you are ready to head off to the gym and keep a close watch on the all important AC Joint.