December 1, 2014
March 23, 2015


Description:  An injury to the acromioclavicular (AC) joint resulting in a sprain/tear of the ligaments. The clavicle articulates distally with the acromion forming a diarthrodial joint with a meniscus centrally. The joint has 4 ligamentous attachments between the distal clavicle and acromion as well as additional support from a ligament anchoring the clavicle to the coracoid, and acromion to the coracoid (See Figure 1)

Figure 1 – Grey’s Anatomy of the AC joint and shoulder showing ligamentous attachments.
AC joint

Mechanism of Injury: May occur due to direct trauma to the anterior joint. This may result from impact with a surface/opponent/wall directly on AC joint or lateral shoulder. Rockwood Classification types IV and VI are quite rare. A type VI may occur with the arm being hyperabducted and externally rotated.

There are 6 types according to the Rockwood classification:

Injury Type Description
Type I No AC displacement, sprain of AC ligaments
Type II Disruption of AC ligaments and displacement of AC joint <100% (can be in same plane as joint or superior displacement of distal clavicular head.
Type III Disruption of AC and CC ligaments displacement <100% (can be in same plane as joint, or superior displacement of distal clavicular head.
Type IV Disruption of AC, CC ligaments and posterior dislocation of clavicular head
Type V Complete disruption of AC and CC ligaments with superior displacement of Clavicular head. >300% displacement
Type VI Complete disruption of AC and CC ligaments with anterior and inferior dislocation of distal clavicular head.

AC – acromioclavicular, CC – Coracoidclavicular


Figure 2 – Illustrations of Rockwood Classification types of AC injuries.
Differential Diagnoses: Clavicle fracture, distal osteolysis of the clavicle, acromioclavicular osteoarthritis, glenohumeral dislocation, glenohumeral sprain, rotator cuff tendinosis, pectoralis major tendinosis/tear, Biceps tenosynovitis.


Inspection – AC prominence, swelling, displacement of clavicle.
Palpation – AC joint, anterior-posterior translation of clavicle.

The AC joint can be easily localized by starting on the clavicle and working distally until an indent is felt, this is the AC joint. Often patients are able to easily demonstrate the location of AC joint by asking the patient to point. The AC joint is usually tender on examination acutely, and will have pain with anterior-posterior translation of the distal clavicular head on the acromion as well as compression tests.

AROM  – Pain may restrict range of motion in all directions soon after the injury.

PROM – may also be painful for patient early in recovery.

Rotator Cuff:  It is important to test range of motion and rotator cuff strength in all patients with suspected AC joint pathology. The patient may describe pain from 100 degrees of abduction up to 150 degrees. There may be a restriction in active range of motion secondary to the acute injury and proximity to the GH joint.  There may be some associated rotator cuff weakness either due to pain or a related rotator cuff injury.

Special Tests:

Scarf testing – consisting of having patient use affected side hand to grab posterior contralateral shoulder, and then pushing it.  It  can be further amplified by having patient elevate their elbow against resistance.


Xray: AP, Zanca views (10-15 degrees cephalic), Stress views (not that useful, uncomfortable for patient) Scapular Y, and axillary. (1,2,3)
US/MRI: If rotator cuff involvement is suspected.


Conservative management:

Stage I – Rest and Sling-Immobilization

Stage II – Range of Motion, Isometric strengthening

Stage III – increased range of motion, and more dynamic strengthening.

Return to play is based on patient’s report of function, clinical exam as well as risk of contact.

Type I injuries may return in 10-14 days.
Type II typically require lengthier rest from contact up 3-6 weeks to allow for ligamentous healing.
Of note, 50% of patients followed up long term after Type I AC injuries had recurrent issues with their AC joint (4).

Type III, if conservative will require at least 6 weeks and may require surgical intervention

Surgical Management: Required for Types IV, V and VI

There are 3 types (1):

  • AC joint fixation – Uses hardware to stabilize the joint
  • Coracoclavicular fixation –Stabilization of distal clavicle to coracoid either anatomically or through screw fixation.
  • Ligamentous Reconstruction – an anatomic reconstruction

Dr. Neil Dilworth ( March 23, 2015)


  • Stucken C, Cohen S. Management of acromioclavicular joint injuries. Orthop Clin North Am. 2015 Jan;46(1):57-66. doi: 10.1016/j.ocl.2014.09.003. Epub 2014 Oct 11.
  • Kim S, Blank A, Strauss E. Management of type 3 acromioclavicular joint dislocations–current controversies. Bull Hosp Jt Dis (2013). 2014;72(1):53-60.
  • Mikek M Long-term shoulder function after type I and II acromioclavicular joint disruption. Am J Sports Med. 2008 Nov;36(11):2147-50. doi: 10.1177/0363546508319047. Epub 2008 Jun 26.