Acromioclavicular (AC) Joint Separation: A Common Injury from Falling and Impacting the Shoulder

Introduction

The acromioclavicular joint (AC joint) is located between the lateral end of the clavicle and the acromion. When a basketball player falls, gets pushed, or battles for position with a shoulder bump, this joint is highly susceptible to sprains or even dislocations.

This article summarizes the Rockwood classification and treatment strategies to help basketball players understand when conservative management is appropriate and when surgery is needed.

Anatomy

The AC joint is stabilized by three groups of ligaments:

• AC ligaments (superior and inferior bundles)
• Coracoclavicular ligament (CC ligament, consisting of the conoid and trapezoid)
• Extensions of the deltoid and trapezius muscles

Mechanism of Injury

• Direct fall with impact to the lateral shoulder (most common)
• Fall on an outstretched arm, with force transmitted upward
• Shoulder compressed and twisted

Rockwood Classification

Grade	Ligaments	Imaging Findings	Management
Type I	AC sprain, CC intact	Normal X-ray	Conservative 1–2 weeks
Type II	AC torn, CC sprain	Mild superior clavicle displacement	Conservative 4–6 weeks
Type III	AC + CC torn	Clavicle displaced 25–100%	Conservative vs. surgery
Type IV	Clavicle displaced posteriorly	Enters the trapezius	Surgery
Type V	Clavicle displaced 100–300%	Severe deformity	Surgery
Type VI	Clavicle displaced inferiorly	Rare	Surgery

Management of Type III remains controversial; current trends suggest surgery may be considered for young patients with high activity demands.

Evaluation

• O’Brien test
• Cross-body adduction test
• Palpation for a step-off deformity at the AC joint
• X-ray (bilateral comparison with weighted views)

Treatment Strategies

Conservative treatment:

• Sling immobilization for 1–2 weeks
• Early ROM
• Progressive strengthening
• Physical therapy: infrared, ultrasound as adjuncts

Surgical treatment:

• Indicated for Type IV–VI and Type III with high activity demands
• Clavicle reduction + ligament reconstruction
• Immobilization for 6 weeks postoperatively

Rehabilitation Timeline

Phase	Conservative	Surgical
Acute	1–2 weeks immobilization	4 weeks immobilization
Early ROM	2–4 weeks	4–8 weeks
Strengthening	4–8 weeks	8–12 weeks
Advanced	8–12 weeks	12–16 weeks
Return to play	8–12 weeks	4–6 months

Practical Recommendations

• Seek medical attention if the shoulder appears “bumped” or deformed after a fall
• A step-off deformity at the AC joint is key to diagnosis
• Type I–II mostly recover fully
• Whether Type III requires surgery should be discussed with an orthopedic sports medicine specialist
• Rehabilitation focus: trapezius, rhomboids, posterior deltoid
• Basketball players may consider a specialized shoulder brace upon return
• National Taiwan University of Sport and Chang Gung Sports Medicine Center offer comprehensive AC joint evaluations

Prevention Strategies

• Strengthen scapular stabilizer muscles
• Learn proper falling techniques
• Core stability for body contact against opponents
• Consider wearing a shoulder brace during games

Conclusion

The defining feature of AC joint sprains is that “grade determines prognosis.” Be sure to obtain imaging-based classification before deciding on the treatment path. The high activity demands and aesthetic considerations of young basketball players should both be taken into account.

Related Reading

• Ankle Sprain Grade I/II/III: A Complete Guide to Courtside Management for Basketball Players
• ACL Tear in Basketball Players: Mechanism, Diagnosis, and Reconstruction Decisions
• Cycling Fracture First Aid: On-Site Management of Clavicle Fractures and When to Return to Riding
• Meniscus Tear Classification and Surgery: Should Basketball Players Get It Sutured?