Which ligament provides stability to the acromioclavicular joint?

The acromioclavicular ligament is crucial for providing stability to the acromioclavicular joint, which connects the clavicle and the acromion of the scapula. This ligament helps to maintain the position of the clavicle relative to the acromion, allowing for proper shoulder function. Its role is to resist forces that could lead to dislocation or instability at the joint, especially during movements that involve lifting the arm.

In contrast, the coracoacromial ligament primarily serves to protect the shoulder joint by forming a protective arch over the humeral head and does not directly stabilize the acromioclavicular joint itself. The glenohumeral ligaments support the glenohumeral joint, which is a different joint involving the humerus and the scapula. Lastly, the capsular ligament refers generally to the ligaments surrounding the shoulder joint and is not specific to the acromioclavicular joint. Therefore, the acromioclavicular ligament stands out as the key structure that stabilizes the acromioclavicular joint itself.