An acromioclavicular (AC) joint separation is a sprain or tear of the ligaments that hold the clavicle to the acromion of the shoulder blade. Commonly called a separated shoulder, it is a different injury from a glenohumeral dislocation and represents disruption of the joint at the top of the shoulder rather than the ball-and-socket joint itself. AC separations are graded I through VI based on which ligaments are torn and how far the clavicle has displaced from the acromion.
What Is an AC Joint Separation?
The acromioclavicular joint is where the clavicle (collarbone) meets the acromion, the bony projection of the scapula that forms the top of the shoulder. Two ligament complexes stabilize this joint. The acromioclavicular ligaments directly connect the clavicle to the acromion and provide horizontal stability. The coracoclavicular ligaments (the trapezoid and conoid) connect the clavicle to the coracoid process below and provide vertical stability, holding the clavicle down against the acromion.
When the shoulder takes a direct blow from above or the side, these ligaments can stretch, partially tear, or completely rupture, allowing the clavicle to displace upward away from the acromion. The more ligaments torn and the greater the displacement, the higher the grade of separation:
- Grade I: stretch of the AC ligaments without displacement
- Grade II: AC ligaments torn, coracoclavicular ligaments intact, minor displacement
- Grade III: both ligament complexes torn with visible clavicle elevation
- Grades IV, V, VI: severe displacement in various directions, with Grade V being the most common high-grade pattern
Causes and Risk Factors
- Direct fall onto the point of the shoulder (the classic mechanism)
- Contact sport collisions, particularly in football, hockey, rugby, and wrestling
- Cycling and motorcycle accidents with falls over the handlebars
- Fall on an outstretched arm with an axial load transmitted through the shoulder
Symptoms
- Pain at the top of the shoulder immediately after the injury
- Visible or palpable step-off deformity at the AC joint in higher-grade injuries, with the clavicle appearing to protrude upward
- Tenderness directly over the AC joint
- Pain with overhead activity, cross-body reaching, and lying on the affected side
- Limited shoulder motion in the acute phase, which often improves as acute pain subsides
Diagnosis
Dr. Chudik’s evaluation includes the mechanism of injury, palpation of the AC joint, and assessment of clavicle position and mobility. X-rays of both shoulders are obtained to compare sides and determine the grade of separation. Weighted or stress views are sometimes added to detect occult instability. MRI is ordered when there is concern for associated rotator cuff injury or to clarify ligament integrity in higher-grade or ambiguous cases. The Westmont office has on-site high-field MRI and X-ray.
Treatment
Non-surgical treatment is the standard for Grade I and Grade II separations and for most Grade III separations in non-overhead laborers. It includes:
- Sling use for one to three weeks for comfort
- Ice and anti-inflammatory medication
- Progressive physical therapy focused on restoring motion and scapular control
- Return to activity as pain and strength allow, typically within six to 12 weeks
Surgery is indicated for Grade IV, V, and VI separations, for active patients with symptomatic Grade III separations, and for elite overhead athletes and heavy laborers whose work requires reliable clavicle mechanics. Dr. Chudik developed the Acromioclavicular (AC) Joint Separation Repair and Reconstruction technique, which restores both the coracoclavicular and acromioclavicular ligaments with the goal of anatomic stability and a lower rate of hardware-related complications than older approaches. The technique is performed through small incisions with graft reconstruction of the torn ligaments.
Recovery and Outcomes
Recovery after non-surgical management of low-grade separations typically allows return to daily activity within two to four weeks and return to sport within six to 12 weeks. Some patients have a persistent bump at the AC joint but full functional recovery.
Recovery after AC reconstruction typically includes six weeks of sling protection, progressive range of motion over two to three months, and strengthening over three to four months. Return to contact sport is typically five to six months. Outcomes are best when the injury is treated before chronic scarring and secondary shoulder mechanics develop.
When to See Dr. Chudik
Schedule an evaluation after any fall onto the shoulder with persistent pain at the top of the shoulder, a visible bump, or difficulty with overhead motion. Call 630-324-0402 or request an appointment online.