AC Joint Injury

AC Joint Sprain

Article by John Miller

AC Joint Sprain

(Acromioclavicular Joint Sprain)

Acromioclavicular Joint

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 and transmits forces from the arm to your body. Several ligaments 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 joint’s socket, and the humerus has a round head that articulates upon the glenoid fossa (socket). The end of the scapula is called the acromion. This part of the scapula and clavicle joint 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. Other names for this injury is acromioclavicular joint separation, 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.

Your 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 your mechanism of injury and a simple physical examination.

X-rays ensure there is no fracture of these bones. Clavicle fractures from falls are prevalent.

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.

For a specific diagnosis regarding your shoulder injury, please consult your shoulder physiotherapist or doctor.

AC Joint Injury Treatment

Physiotherapy

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. It is crucial to protect your AC joint ligaments from overstretching the immature scar tissue during this time. 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.

Surgery

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 completing 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

Adhesive Capsulitis

Shoulder Bursitis

Shoulder Instability

Acromioclavicular Joint

Bone Injuries

Post-Operative Physiotherapy

Muscle Conditions

Systemic Conditions

Referred Pain

Shoulder Treatment

Researchers have discovered that managing your shoulder injury with physiotherapy is usually successful. Typically, you have two options: a 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  - either trial a non-operative/conservative treatment approach or condition and prepare your shoulder and body for a surgical procedure.

Post-operative physiotherapy will safely regain your normal range of movement, strength and function.

PhysioWorks physiotherapists have a particular 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 to attain the best possible outcome for your shoulder injury.

For specific information regarding your shoulder, please consult your trusted shoulder physiotherapist.

Acute Injury Signs

Acute Injury Management.

Here are some warning signs that you have an injury. While some injuries are immediately evident, others can creep up slowly and progressively get worse. If you don't pay attention to both types of injuries, chronic problems can develop.

For detailed information on specific injuries, check out the injury by body part section.

Don't Ignore these Injury Warning Signs

Joint Pain

Joint pain, particularly in the knee, ankle, elbow, and wrist joints, should never be ignored. Because these joints are not covered by muscle, pain here is rarely of muscular origin. Joint pain that lasts more than 48 hours requires a professional diagnosis.

Tenderness

If you can elicit pain at a specific point in a bone, muscle, or joint, you may have a significant injury by pressing your finger into it. If the same spot on the other side of the body does not produce the same pain, you should probably see your health professional.  

Swelling

Nearly all sports or musculoskeletal injuries cause swelling. Swelling is usually quite obvious and can be seen, but occasionally you may feel as though something is swollen or "full" even though it looks normal. Swelling usually goes along with pain, redness and heat.

Reduced Range of Motion

If the swelling isn't obvious, you can usually find it by checking for a reduced range of motion in a joint. If there is significant swelling within a joint, you will lose range of motion. Compare one side of the body with the other to identify major differences. If there are any, you probably have an injury that needs attention.

Weakness

Compare sides for weakness by performing the same task. One way to tell is to lift the same weight with the right and left sides and look at the result. Or try to place body weight on one leg and then the other. A difference in your ability to support your weight is another suggestion of an injury that requires attention.

Immediate Injury Treatment: Step-by-Step Guidelines

  • Stop the activity immediately.
  • Wrap the injured part in a compression bandage.
  • Apply ice to the injured part (use a bag of crushed ice or a bag of frozen vegetables).
  • Elevate the injured part to reduce swelling.
  • Consult your health practitioner for a proper diagnosis of any serious injury.
  • Rehabilitate your injury under professional guidance.
  • Seek a second opinion if you are not improving.