AC Joint Sprains: The Rockwood Classification and Conservative Management
In short
Rockwood Types I and II AC joint sprains heal reliably with sling protection; Type III separations manage conservatively without long-term functional deficits.
In this guide (4 sections)
Anatomy and Mechanism of AC Joint Disruptions
Acromioclavicular (AC) joint separations (commonly termed shoulder separations) represent roughly 40% of all athletic shoulder injuries, highly prevalent in rugby, hockey, football, and cycling. The injury almost universally results from a direct fall onto the lateral tip of the shoulder with the arm adducted.
The impact forces the acromion downward and medially, while the clavicle remains held in place. The primary static restraints - the Acromioclavicular (AC) ligaments (which resist horizontal anteroposterior translation) and the Coracoclavicular (CC) ligaments (trapezoid and conoid ligaments, which resist vertical displacement) - fail progressively depending on impact velocity.
The Rockwood Classification System
| Rockwood Type | Ligamentous Disruption | Clavicular Displacement (X-ray) | Management and Return-to-Play Timeline | |
|---|---|---|---|---|
| Type I (Mild Sprain) | AC ligament sprained/partially torn; CC ligaments completely intact | Normal alignment; zero vertical displacement | Conservative; sling 2 to 5 days; return to play 1 to 2 weeks | |
| Type II (Partial Separation) | AC ligament completely torn; CC ligaments sprained but intact | Mild vertical displacement (< 25% clavicle height) | Conservative; sling 1 to 2 weeks; return to play 3 to 4 weeks | |
| Type III (Complete Separation) | Both AC and CC ligaments completely torn; deltotrapezial fascia torn | Clavicle elevated 25% to 100% above acromion ('piano key' sign) | Controversial: Conservative physiotherapy yields equal outcomes to surgery in athletes | |
| Type IV (Posterior Displacement) | Complete tear of AC and CC; clavicle displaced posteriorly into trapezius | Clavicle buttonholed through trapezius muscle belly | Surgical reduction and CC ligament reconstruction mandatory | |
| Type V (Severe Superior) | Complete disruption with extreme elevation (100% to 300% above acromion) | Dramatic step-off; clavicle tenting skin dangerously | Surgical reconstruction mandatory | |
| Type VI (Inferior Displacement) | Clavicle displaced inferiorly beneath coracoid process (rare, high trauma) | Subcoracoid entrapment; neurovascular compromise | Urgent surgical reduction mandatory |
Rehabilitation Protocol for Type I, II, and III Separations
- The Kenny-Howard Sling Controversy: Avoid rigid upward-pushing Kenny-Howard slings; modern evidence proves they do not reduce the clavicle and cause skin ulcerations. Use a simple comfort sling for 5 to 10 days.
- Cross-Body Horizontal Adduction Avoidance: Avoid reaching across the body (cross-body adduction) for the first 3 weeks; this movement shears the healing AC joint capsule.
- Deltoid and Trapezius Dynamic Compensation: Strengthen the anterior and lateral deltoid alongside the upper and middle trapezius; these muscles cross the AC joint and provide dynamic muscular stability to compensate for torn ligaments.
Frequently Asked Questions
What is the 'piano key' sign in a separated shoulder?
The piano key sign occurs when your clavicle sticks up high after tearing its ligaments. If you press down on the bone, it springs down like a piano key and then pops right back up when you let go.
Will having a permanent bump on my shoulder affect my athletic performance?
For Type 2 and 3 injuries, a cosmetic bump remains permanently, but research shows that athletes regain full strength, throwing velocity, and range of motion without surgery.
When can I play contact sports again after an AC joint sprain?
Type 1 sprains return in 10 to 14 days. Type 2 and 3 sprains take 4 to 8 weeks. You can return once you can do a full push-up, take a direct bump to the shoulder, and reach across your chest without pain.
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