AC Joint Sprain
(Acromioclavicular Joint Sprain)
An acromioclavicular (AC) joint injury is commonly referred to as “shoulder separation” and should not be confused with a shoulder dislocation.
Your acromioclavicular joint (or AC Joint) is the joint at the top of your shoulder between your clavicle (collarbone) and your scapula (shoulder blade). The AC joint is essential. It allows overhead and across your body shoulder movements, as well as transmitting forces from the arm to your body. There are several ligaments which help to stabilise this joint.
An acromioclavicular joint sprain is a ligament overstretching injury. The degree of AC joint ligament damage can vary from a mild strain of one or more of the surrounding ligaments to complete ligament tears and deformity.
What is the AC Joint?
The shoulder joint forms at the junction of three bones. The collarbone (clavicle), the shoulder blade (scapula), and the arm bone (humerus). The scapula forms the socket of the joint, and the humerus has a round head that articulates upon the glenoid fossa (socket). The end of the scapula is called the acromion. The joint between this part of the scapula and clavicle is called the acromioclavicular joint (AC joint).
When the acromioclavicular joint overstretches, it is called a shoulder separation and can form a “step” if displaced. Another name for this injury is an acromioclavicular joint separation, or AC separation or an AC joint sprain.
The ligaments include the acromioclavicular, coracoacromial and coracoclavicular (trapezoid and conoid) ligaments.
What Causes an AC Joint Injury?
Direct forces can injure your AC joint when a person collides with a solid object or surface such as a fall from a bicycle or during a football tackle where the shoulder hits the ground.
You acromioclavicular joint may also be injured indirectly when a person falls on an outstretched arm. The contact force transmitted up through the arm forces a separation of the acromion and clavicle. The ligaments are overstretched and damaged in the process.
AC Joint Injury Symptoms
Your physiotherapist will suspect an acromioclavicular ligament sprain when you report:
- Pain on the top of the shoulder aggravated by heavy lifting, overhead and across body movements.
- Swelling +/- bruising.
- Loss of shoulder movement.
- Sometimes a hard, visible lump may also be present on the top of the shoulder, indicating the displacement of the clavicle (collar bone).
AC joint injury is graded by severity from Grade I (minimal joint disruption) to Grade III (severe damage). If the injury is the more severe, Grade III, a bump caused by the separated AC joint may be seen or felt at the tip of the shoulder bones. The diagnosis of shoulder separation is often quite apparent from hearing a story that is typical of this injury, and a simple physical examination.
X-rays ensure there is no fracture of these bones. Clavicle fractures from falls are particularly common.
If the diagnosis is unclear, X-rays while holding a weight in your hand may be helpful. With this X-ray, the force of the gravity will accentuate any AC joint instability and better show the effects of the separated shoulder.
AC Joint Injury Treatment
Most patients with acromioclavicular joint injury start to feel better within a few days or a week of the damage. However, full ligament healing will take at least six weeks. During this time, it is crucial to protect your AC joint ligaments from overstretching the immature scar tissue. It can be helpful to use a sling, taping or a shoulder brace that de-loads your AC joint.
Your physiotherapist’s treatment will aim to:
- Reduce pain and inflammation.
- Normalise joint range of motion.
- Strengthen your shoulder.
- Improve your shoulder blade and shoulder alignment.
- Normalise your muscle lengths.
- Improve your upper limb proprioception.
- Improve your technique and function, e.g. lifting, overhead activities.
- Minimise your chance of re-injury as you return to sport or work.
In severe cases, some patients choose to undergo AC joint surgery to pin the AC joint or repair the damaged ligaments surrounding the AC joint.
Post-operative rehabilitation is one of the most important, yet too often neglected, aspects of surgery. The quickest and most successful outcomes result from the guidance and supervision of an experienced shoulder physiotherapist.
Your rehabilitation following shoulder surgery focuses on restoring full shoulder motion, strength, power and endurance. You will also require proprioception and individualised functional-based retraining towards your specific needs.
Risks of surgery include infection, persistent instability and pain, stiffness, and difficulty returning to your previous level of activity.
Return to Sports with an AC Joint Injury
When returning to your sport, you must undergo a graduated transition to avoid the risk of injury recurrence. This rehabilitation includes the completion of a full individually designed rehabilitation program aimed at improving strengthening, flexibility and proprioception in your upper limbs.
For more information, please ask the advice of your physiotherapist.
Common Shoulder Pain & Injury Conditions
- Rotator Cuff Syndrome
- Shoulder Tendinopathy
- Rotator Cuff Calcific Tendinopathy
- Rotator Cuff Tear
- Bicep Tendinopathy
- Shoulder Impingement
- Swimmer's Shoulder
- Shoulder Dislocation (Instability)
- Subacromial Decompression
- Shoulder Arthroscopy
- Rotator Cuff Repair
- SLAP Repair
- Biceps Tenodesis
- Biceps Tenotomy
- Total Shoulder Replacement
Researchers have discovered that managing your shoulder injury with physiotherapy is usually successful. Typically, you have two options: non-operative or a surgical approach. Your condition will dictate which option is best for you at this time. Non-operative care is conservative rehabilitation.
If shoulder surgery is required, then your physiotherapist may undertake:
- Pre-operative rehabilitation - to either try a non-operative treatment approach or to condition and prepare your body for a surgical procedure.
- Post-operative physiotherapy - to safely and methodically regain your normal range of movement, strength, speed and function.
PhysioWorks physiotherapists have a special interest and an excellent working relationship with leading shoulder surgeons. Our physiotherapy team provide you with both conservative and post-operative shoulder rehabilitation options. We aim for you attaining the best possible outcome for your shoulder injury.