Sports Medicine
Sports Injury Prevention & Rehabilitation

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AC Joint Sprain

(Also known as an Shoulder Separation, AC Joint Injury, Sprained AC Joint, Torn AC Joint, AC Joint Subluxation, AC Joint Dislocation, Acromioclavicular Joint Injury)
What is an AC joint sprain?
An AC joint sprain is a relatively common sporting injury affecting the shoulder and is characterized by tearing of the connective tissue and ligaments of the Acromio-Clavicular joint.
The shoulder blade gives rise to a bony prominence known as the acromion. The acromion attaches to the collar bone (clavicle) via strong ligaments and connective tissue. This joint is known as the AC joint and is situated at the point of the shoulder.
The AC joint is responsible for connecting the shoulder blade with the clavicle and allows for some shoulder movement. During certain activities, stretching forces are placed on the AC joint. When these forces are excessive and beyond what the AC joint can withstand, tearing of the ligaments and connective tissue of the AC joint may occur. This condition is known as an AC joint sprain.
An AC joint sprain can range from a small sprain resulting in minimal pain and allowing ongoing activity, to a severe sprain resulting in significant pain, deformity and disability.

Causes of an AC joint sprain

An AC joint sprain typically occurs due to a specific incident such as a direct blow to the point of the shoulder. This commonly occurs in contact sports due to a collision with another player or following a fall onto the point of the shoulder.

Signs and Symptoms of an AC joint sprain
Patients with this condition typically experience a sudden onset of pain on the top of the shoulder at the time of injury. Pain may increase with activities involving lying on the affected side, moving the arm across the body, overhead activity or performing heavy lifting, pushing or pulling movements with the affected arm. In minor cases of an AC joint sprain, patients may be able to continue activity only to experience an increase in pain, swelling and stiffness in the shoulder after activity with rest (particularly first thing in the morning).
In more severe cases, pain may prevent the patient from continuing activity and cause them to cradle the arm. Patients may also experience a rapid onset of swelling and may notice a 'step' deformity or bump in their shoulder with the tip of their collar bone sticking up. This occurs due to tearing of the connective tissue holding the AC joint together and the accumulation of swelling and bleeding around the joint.

Diagnosis of an AC joint sprain

A thorough subjective and objective examination from a physician is usually sufficient to diagnose an AC joint sprain. Investigations such as an X-ray, MRI scan or CT scan may occasionally be required to confirm diagnosis and determine the extent of damage or involvement of other structures. This is often important to exclude the possibility of a fracture.

Treatment for an AC joint sprain

Most patients with this condition heal well with appropriate physical therapy. The success rate of treatment is largely dictated by patient compliance. A vital aspect of treatment is that the patient rests sufficiently from any activity that increases their pain until they are pain free (a sling may be required initially). Activities placing large amounts of stress on the AC joint should also be minimized, particularly lifting, pushing, pulling, overhead activity, lying on the affected side and movements taking the arm across the body. Resting from aggravating activities ensures the body can begin the healing process in the absence of further tissue damage. Once the patient can perform these activities pain free a gradual return to these activities is indicated provided there is no increase in symptoms.
Ignoring symptoms or adopting a 'no pain, no gain' attitude is likely to lead to the condition becoming chronic. Immediate, appropriate treatment in patients with an AC joint sprain is essential to ensure a speedy recovery. Once the condition is chronic, healing slows significantly resulting in markedly increased recovery times and an increased likelihood of future recurrence.
Patients with an AC joint sprain should follow RICE in the initial phase of injury. RICE is beneficial in the first 72 hours following injury or when inflammatory signs are present (i.e. morning pain or pain with rest). RICE involves resting from aggravating activities (this may include the use of a sling), regular icing, and keeping the arm elevated (e.g. lying on the unaffected side). Anti-inflammatory medication may also significantly hasten the healing process by reducing the pain and swelling associated with inflammation.
Patients with an AC joint sprain should also perform pain-free flexibility and strengthening exercises as part of their rehabilitation to ensure an optimal outcome. The treating physical therapist can advise which exercises are most appropriate for the patient and when they should be commenced.
Upon return to sport (especially contact sports), patients with this condition should usually tape the shoulder to protect and support the AC joint and decrease the likelihood of re-injury.

Prognosis of an AC joint sprain
With appropriate management, most patients with a minor to moderate AC joint sprain can return to sport or normal activity within 2 – 8 weeks. Patients with severe AC joint injuries will usually require a longer period of rehabilitation to gain optimum function.

Physical therapy for an AC joint sprain
Physical therapy for patients with this condition is vital to hasten the healing process, ensure an optimal outcome and reduce the likelihood of future recurrence. Treatment may comprise:
  • soft tissue massage
  • joint mobilization
  • ice or heat treatment
  • electrotherapy (e.g. ultrasound)
  • protective taping
  • the use of a sling
  • anti-inflammatory advice
  • exercises to restore flexibility and strength
  • education
  • activity modification advice
  • a gradual return to activity program

Other intervention for an AC joint sprain
Despite appropriate physical therapy management, a small percentage of patients with an AC joint sprain do not improve adequately. When this occurs the treating physical therapist or doctor can advise on the best course of management. This may involve pharmaceutical intervention, corticosteroid injection, further investigation such as an X-ray, CT scan or MRI, or a review by a specialist who can advise on any procedures that may be appropriate to improve the condition.