An AC joint sprain is an injury that usually results from a fall onto your shoulder or onto an arm restraining your fall. It is a sprain of the acromioclavicular (AC) joint ligaments that connect the clavicle (collar bone) to the shoulder blade.
The impact of the fall can damage the shoulder ligaments holding the shoulder blade close to the collar bone. When this happens, the space between the two bones widens. Another name for this injury is “shoulder separation”.
The injury occurs frequently in contact sports in which athletes frequently fall or collide with each other. Sports like football, rugby, cycling or snowboarding are often involved.
AC joint sprains typically cause shoulder pain and swelling (among other symptoms) near the the injured ligaments. The shape of the shoulder may also change. More details are provided below.
The good news is that AC joint injuries are usually treatable by non invasive methods such as resting and icing the injured shoulder. Again, this is explained in more detail below.
A knowledge of the various parts of the shoulder joint is helpful in understanding the symptoms of this injury and how they are treated.
The shoulder actually has three bones and two joints. The three bones are the upper arm bone (humerus), the collarbone (clavicle) and the shoulder blade itself (the scapula).
The upper arm connects to the shoulder blade in a ball and joint arrangement. This is called the glenohumeral joint. This is the location of the rotator cuff tendons.
The shoulder blade and the collar bone meet at the highest point of the latter (called the acromion). This is the acromioclavicular joint and the two bones are held together by several strong ligaments. These are the ligaments that are damaged when an AC joint sprain occurs.
The ac ligaments (acromioclavicular ligaments) hold the two bones together in the horizontal plane). At the same time, the coracoclavicular (cc) ligaments hold them together in the vertical place. Both the ac and cc ligaments may be injured when you experience an AC joint sprain.
Causes Of An AC Joint Sprain
As mentioned above, typical causes of this injury are a fall directly onto your shoulder or onto an outstretched arm you are using to try and break a fall.
It can also occur if you suffer a direct flow to the shoulder as a result of colliding with someone or something.
Diagnosis usually takes the form of physical inspection of the injured shoulder. AC joint sprains usually result in a noticeable bump on the shoulder due to the raising of the collar bone. The shoulder bone itself may have a characteristic “drooping” appearance.
These deformities make diagnosis a relatively simple matter. If the doctor has any doubt, asking the patient to hold a small weight increases the deformity to the point that it becomes clear on an X ray image.
Symptoms & Treatment
The symptoms of an AC joint sprain can vary widely depending on the injury’s severity.
Grade 1 Sprain
This involves only stretching of the capsule covering the joint but no damage to the ligaments holding the joint together. You may experience swelling at the point of the injury together with mild pain.
The appropriate treatment for any AC joint sprain is rest for your shoulder. Avoid lifting or other actions that might stress the joint. Using a shoulder brace or arm sling can help reduce stress on the shoulder and speed the healing process.
To control the pain, you may use an over the counter pain killer like Tylenol. Icing or a cold compress may also help to control the swelling.
The symptoms may last for 2-4 weeks but usually then disappear with no need for surgery or more aggressive treatment.
Grade 2 Sprain
A grade 2 sprain usually involves tearing of the capsule covering the joint. In addition, the ligaments holding the shoulder blade and collarbone may be stretched (but not torn). The symptoms will usually include joint pain, swelling and possibly some bruising at the location of the joint. A small but permanent bump may appear on your shoulder over the point where the shoulder blade meets your collarbone.
As with a grade 1 sprain, resting your shoulder, together with use of a shoulder support or arm sling, will help to resolve the injury. Icing your shoulder for 20 minutes at a time and at intervals of 2-3 hours will also help ease the pain. Pain killers can also be used to control the pain and swelling.
The pain will typically last for 4-6 weeks but then disappear, leaving only the bump. Again, surgery is usually not required.
Grade 3-5 Sprains
These involve tearing of both the capsule covering the joint and the ligaments connecting the shoulder and collar bones. The most serious injury (Grade 5) involves the collar bone tearing through the sheath of muscle (fascia) that normally covers it.
These injuries normally cause pain for 4-8 weeks. At the end of this period a small permanent bump may appear at the shoulder point where the AC joint is located.
AC joints with severity corresponding to grades 3 or 4 are usually treatable as described for 1 and 2. Resting the shoulder, together with application of ice and possibly pain killing medication, should be adequate. A non steroidal anti inflammatory medication may also be considered for control of swelling in addition to pain.
If these steps do not resolve the pain, approach your doctors for further medical advice. Surgery may be required to correct the problem. Doctors may also suggest surgery right away if the injury is a grade 5 one.
Physical therapy is normally part of the treatment once the pain has started to recede. A physical therapist can design an exercise program to strengthen your shoulder ligaments and improve their suppleness. This will help you regain normal shoulder function and reduce the chances of another AC sprain in your future.