March 23, 2015
May 11, 2015


Description:  The acromioclavicular joint is a diarthrodial joint with a meniscus located centrally.   The joint is stabilized by 4 surrounding ligaments and 2 additional ligamentous supports: The coracoclavicular ligament and the coraco-acromial ligament. Osteoarthritis involves narrowing of the acromioclavicular space and degeneration or disintegration of the meniscus.
1)   Joint Space Narrowing
2)   Subchondral Cysts – cystic changes in the distal aspect of the joint under the cartilage
3)   Osteosclerosis – thickening of the cortex
4)   Osteophytes – Boney outgrowths from the joint.

As the joint as part of the roof to the rotator cuff, enlargement of the joint from osteophytosis can lead to encroachment onto the supraspinatus tendon. Cocommitant rotator cuff disease and biceps tendinosis are very common. (1) Common sports that affect the AC joint through repetitive microtrauma – weight lifting, swimming, and overhead sports.

Mechanism of Injury: Osteoarthritis of the AC joint may be primary (degenerative) or secondary to trauma or sepsis. Approximately 50% of patients who suffered AC type I or II injuries ended up having long-term issues with their AC joint.(2)

Differential Diagnosis:

AC separation, 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, crepitus with AROM of shoulder.

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 (Crossover/Adduction test) – 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), Scapular Y, and axillary. (1,3)

Figure 1 – Osteoarthritis of AC joint on AP view.
US/MRI: If rotator cuff or biceps involvement is suspected.

Activity modification: Reduction of aggravating activities. Modifications of activities like swimming may involve the patient using a flutter board in the pool.   For patients active in the gym, avoiding press ups, shoulder presses, and dips may be of great assistance.
Analgesia – Icing, heat, NSAIDs, acetaminophen, topical NSAIDs
Injections – Cortisone – this can help both diagnostically and therapeutically.
Physiotherapy – May focus on manual therapy, rotator cuff strengthening, scapular stabilization and modalities to reduce pain.


Resection of distal clavicle either open or arthroscopically (1).
Dr. Neil Dilworth (March 23, 2015)


  • Mall N, Foley E, Chalmers P, Cole B, Romeo A, Bach B. Degenerative joint disease of the acromioclavicular joint: a review. Am J Sports Med. 2013 Nov;41(11):2684-92. doi: 10.1177/0363546513485359. Epub 2013 May 6.
  • 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.