The AC joint or acromioclavicular joint is the area on top of the shoulder where the acromion process of the scapula connects with the lateral part of the clavicle. Take note that the joint allows the shoulder blade to slide on the rear part of the rib cage. The rotational component of the joint allows the full range of motion of the arm overhead. An injury to the AC joint is common where the individual falls on an outstretched arm or if the body weight lands directly on the joint. The dislocation of the joint is the most prevalent type of injury and commonly seen among those who engage in contact sports.
It is important to note that pain is the initial symptom of an AC joint injury. It is the signal of the body that damage was sustained and indicates that the individual should be careful when using the affected arm. The pain is usually felt right after the injury was sustained. The symptoms are present due to the tears in the ligaments that support the joint together. Supporting the arm with a sling can help reduce the strain on the ligaments, thus minimizing the symptoms. You can apply an ice pack for 20 minutes at a time since it can effectively manage pain. By enrolling in a first aid course, you can learn how to properly perform these measures.
Edema or swelling in the joints is another response of the body to injury. Since the AC joint is small in size, the degree of swelling within the joint space is also minimal. Any increase in the amount of fluid in the joint space adds pain in the shoulder and limits the movement of the arm. Swelling can be managed with ice packs along with non-steroidal anti-inflammatory drugs (NSAIDs).
Limited range of motion
Injury to the acromioclavicular joint will lead to poor biomechanics of the joint as well as the inability to completely raise the arm over the head. The ligaments that hold the joint together provide stability that enables the shoulder blade to move on the fixed collar bone. Tears on the ligament diminish this stability and results to abnormal movement. If the tears on the ligaments are minor, the range of motion is slightly affected especially with throwing motions. Physical therapy is often required to restore the full range of motion of the affected limb.
Depending on the severity of the injury to the AC joint, it can also involve the musculature of the shoulder joint. Tears on the shoulder muscles can lead to the inability to produce normal muscular contraction and the individual will notice weakness. Severe tears would require surgery but minor injuries typically improve with rest and steady return to normal use of the arm.
Dislocation of the joint
The degree of damage to the AC joint is defined by grades of dislocation. The grading starts from Grade 1 which is minor up to Grade 6 which requires surgical repair.