If someone has an AC joint pathology, what kind of movement will likely cause pain and instability?

Individuals with an acromioclavicular (AC) joint pathology often experience pain and instability especially during movements that involve significant stress on the joint. Abduction is a movement that requires the arm to move away from the body, which places tension on the structures of the AC joint. This tension can exacerbate pain in a pathological condition since the ligaments and cartilage may be compromised, leading to increased instability.

During abduction, not only is there movement at the shoulder joint, but the AC joint also plays a crucial role in allowing the necessary ranges of motion. If there is an injury or degeneration at the AC joint, the compromised integrity of the joint can result in pain and increased movement between the clavicle and the acromion, causing further instability. Thus, abduction is particularly implicated in exacerbating symptoms of AC joint pathology compared to other movements like flexion or extension, which may not place the same levels of stress on this specific joint.