Shoulder

AC Joint Injury / Separation

An AC joint separation (sometimes called a "separated shoulder") is a disruption of the ligaments connecting the collarbone to the shoulder blade. It is among the most common shoulder injuries in contact athletes and cyclists. At Maryland Orthopedic Specialists, our sports medicine team accurately classifies every AC joint injury and provides targeted treatment, from conservative management of mild separations to surgical reconstruction of higher-grade injuries, with the goal of returning you to full activity as safely and efficiently as possible.

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What is ac joint injury / separation?

The acromioclavicular (AC) joint is the articulation between the lateral end of the clavicle and the acromion process of the scapula. It is stabilized by the coracoclavicular ligaments. Injuries are common in sports and in cycling. Low grade injuries are self-limited.

The acromioclavicular (AC) joint is the articulation between the lateral end of the clavicle and the acromion process of the scapula. Two sets of ligaments maintain its integrity:

AC ligaments (anterior, posterior, superior, inferior): Provide horizontal stability; resist anteroposterior translation of the clavicle
Coracoclavicular (CC) ligaments — trapezoid (lateral) and conoid (medial): Provide vertical stability; resist superior displacement of the clavicle relative to the acromion

AC joint separations most commonly result from a direct fall onto the point of the shoulder (point-of-impact mechanism), forcing the acromion inferiorly while the clavicle maintains its position, progressively tearing these ligaments.

Rockwood Classification (Grades I–VI)

The Rockwood classification is the universally used grading system:

Rockwood Classification:

Grade I — AC ligament sprain; no displacement; managed non-operatively
Grade II — AC ligament torn, CC ligaments sprained; slight displacement (<25% CC widening); managed non-operatively
Grade III — AC and CC ligaments torn; 25–100% superior displacement; management controversial
Grade IV — Clavicle displaced posteriorly into trapezius; operative
Grade V — Severe superior displacement (100–300%); operative
Grade VI — Clavicle displaced inferiorly (subcoracoid); rare; operative

Grade III injuries are the most debated: outcomes of non-operative and operative management are roughly equivalent for most patients, and initial conservative management with delayed surgical decision-making is supported by current evidence.

Symptoms — do you recognize these?

Pain directly over the AC joint at the top of the shoulder
Visible or palpable "bump" at the AC joint (clavicle prominence) in higher-grade injuries
Pain with cross-body adduction (reaching across the chest)
Difficulty lifting the arm overhead or carrying weight
Acute tenderness to palpation at the distal clavicle
A sensation of the shoulder "dropping" in severe separations

Call us at (301) 515-0900. Same-day appointments available at our Bethesda and Germantown locations.

How we diagnose it

Physical Examination

Direct palpation of the AC joint elicits pain. The degree of clavicular displacement relative to the acromion is assessed visually and by gentle piano-key testing (pushing down on the elevated clavicle). Cross-body adduction (horizontal adduction) stresses the AC joint and reproduces pain. In higher-grade injuries, gross deformity is evident.

Imaging

X-rays (bilateral Zanca views, 10° cephalic tilt): Bilateral comparison views allow accurate measurement of the CC distance (normal 11–13 mm); an increase of >5 mm or >25% relative to the contralateral side confirms ligamentous disruption. Stress views (weighted or manual distraction) can unmask Grade II injuries that appear normal on non-stress images.
Axillary view: Essential for identifying posterior clavicular displacement (Grade IV) that may be missed on AP view.
MRI: Useful for determining if the coracoclavicular ligaments have been torn.

Distinguishing from Clavicle Fracture

A clavicle fracture can mimic AC joint injury clinically. X-rays of the full clavicle, not just the AC joint, are essential whenever a bony injury is suspected. Point tenderness over the shaft or midclavicle and deformity away from the AC joint suggest fracture rather than separation.

Treatment options

Non-Operative (Grades I and II, Most Grade III)

- Sling immobilization for 1–2 weeks followed by progressive range-of-motion and strengthening exercises - Ice and NSAIDs for acute pain management - Physical therapy targeting scapular stabilization, rotator cuff strengthening, and AC joint protection - Return to sport typically within 2–6 weeks for Grade I–II; 6–12 weeks for Grade III managed conservatively

Surgical Procedure

AC Joint Reconstruction

Surgical reconstruction of the acromioclavicular joint for high-grade separations (grade III–V), restoring the normal relationship between the clavicle and acromion using ligament transfer, allograft, or synthetic augmentation.

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Recovery & rehabilitation

Grade I–II: Return to contact sport 2–4 weeks with protective padding; full return 4–6 weeks
Grade III (non-operative): Return to full activity 6–12 weeks; most patients achieve excellent outcomes
Operative (Grades IV–VI or failed Grade III): Sling 4–6 weeks; full ROM by 3 months; return to contact sport 4–6 months

Frequently Asked Questions

Do I need surgery for a Grade III separation?

Not necessarily. The majority of Grade III patients do well with conservative treatment. Surgery is considered after 3–6 months of failed non-operative care or in high-demand athletes with persistent functional limitation.

Why does my shoulder still have a bump after treatment?

A residual cosmetic prominence is common with Grade II and III injuries even after full functional recovery. This does not indicate treatment failure and rarely requires intervention.

Can I play sports with an AC separation?

Grade I–II injuries can often return to sport with padding when pain-free. Higher-grade injuries require more structured rehabilitation and medical clearance before contact activities.

How long does it take to recover from an AC joint separation?

Recovery from a Grade I or II AC joint separation typically takes two to six weeks of relative rest, ice, and gentle range-of-motion exercises, followed by a gradual return to full activity. Grade III injuries treated non-surgically may require six to twelve weeks before return to sport, particularly contact sports. Surgically treated high-grade separations generally require three to four months of rehabilitation before full return to throwing or overhead activities. At MOS we use functional milestones, not just time, to clear patients for return to sport.

What are the long-term risks if a Grade III AC separation is not treated surgically?

The majority of patients with Grade III AC separations do well with non-surgical treatment and can return to full activity. A small proportion experience persistent pain, weakness with overhead lifting, or late development of AC joint arthritis from the residual malalignment. The visible bump at the top of the shoulder (due to the displaced clavicle) is permanent in patients treated without surgery. Your MOS surgeon will discuss the likelihood of each outcome based on your activity demands, shoulder dominance, and the specific characteristics of your injury.

Meet the specialists

Christopher S. Raffo, MD

Orthopedic Surgery · Sports Medicine · Knee & Shoulder Arthroscopy · Joint Replacement

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John J. Christoforetti, MD

Orthopedic Surgery · Sports Medicine · Hip, Knee & Shoulder Arthroscopy · Shoulder Replacement

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James S. Gardiner, MD

Orthopedic Surgery · Sports Medicine · Knee & Shoulder Arthroscopy · Knee Replacement

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Related conditions

AC Joint Arthritis Clavicle Fracture

Medically reviewed by Christopher S. Raffo, MD

Last reviewed May 1, 2026

References

Rockwood CA Jr, Williams GR, Young DC. Disorders of the acromioclavicular joint. In: Rockwood CA Jr, Matsen FA, eds. The Shoulder. 2nd ed. Philadelphia, PA: Saunders; 1998:483–553.
Mazzocca AD, Arciero RA, Bicos J. Evaluation and treatment of acromioclavicular joint injuries. Am J Sports Med. 2007;35(2):316–329. doi: 10.1177/0363546506298022.
Lädermann A, Gueorguiev B, Stimec B, Fasel J, Rothstock S, Hoffmeyer P. Acromioclavicular joint reconstruction: a comparative biomechanical study of three techniques. J Shoulder Elbow Surg. 2013;22(2):171–178. doi: 10.1016/j.jse.2012.06.004.
Mouhsine E, Garofalo R, Crevoisier X, Farron A. Grade I and II acromioclavicular dislocations: results of conservative treatment. J Shoulder Elbow Surg. 2003;12(6):599–602. doi: 10.1016/S1058-2746(03)00195-3.
Nissen CW, Chatterjee A. Type III acromioclavicular separation: results of a recent survey on its management. Am J Orthop. 2007;36(2):89–93. PMID: 17393010.
American Academy of Orthopaedic Surgeons. Acromioclavicular Joint Injuries (Shoulder Separation). OrthoInfo. https://orthoinfo.aaos.org/en/diseases--conditions/acromioclavicular-joint-injuries-shoulder-separation/