Acromioclavicular (AC) Joint injury is an injury occurring to the top (point) of the shoulder (where the front of the shoulder blade, called the acromion, meets the collarbone, or clavicle). It can be caused by repetitive overuse, especially with overhead motions, or by a traumatic event, such as a fall directly on the outside of the shoulder. AC Joint injuries most commonly occur in individuals younger than 35 years of age, with males 5 times more likely to sustain a more traumatic AC Joint injury than females. This age population is more prevalent due to the participation in high risk and collision activities, such as football, biking, snow sports, rugby, and ice hockey. The great news is that AC Joint injuries can be identified and effectively treated by a Physical Therapist, often avoiding the need for surgery.
WHAT EXACTLY ARE ACROMIOCLAVICULAR (AC) JOINT INJURIES?
There are 4 ligaments (ligaments go from bone to bone and provide stability) holding the 2 bones of the AC joint together (acromion and clavicle). When there is an injury to the AC Joint the ligaments are stressed, resulting in tears or partial tears that lead to some degree of joint separation. There are 2 types of injuries that can occur at the AC Joint: TRAUMATIC and OVERUSE injuries.
A TRAUMATIC AC Joint injury happens when there is a disruption of the joint because of damaged ligaments holding the 2 bones of the joint together. This type of injury is also known as a SHOULDER SEPARATION (as opposed to a SHOULDER DISLOCATION, which involves the ball and socket joint of the shoulder). Traumatic AC Joint injuries are most common in people who experience a fall on the outside of the shoulder or a fall on an outstretched hand, such as a football player who is tackled or who dives for a pass, a bicyclist who crashes, or a construction worker or homeowner who falls off of a ladder. Traumatic AC Joint injuries are graded from mild to severe based on the amount of separation of the joint. Treatment of mild to moderate cases would most likely be addressed by a Physical Therapist. More severe cases may first require surgery followed by Physical Therapy.
OVERUSE AC Joint injuries occur over time as repetitive stress is placed on the joint. Over time, cartilage that lines and protects the ends of the bones begins to deteriorate, leading to arthritis. OVERUSE AC Joint injuries are most common with sports or occupations that require repetitive overhead motions (swimmers, tennis players, painters, drywallers), or individuals who perform tasks such as heavy weightlifting (most notably military presses).
WHAT SYMPTOMS WOULD I NORMALLY FEEL WITH AN AC JOINT INJURY?
Typical symptoms include:
- General shoulder pain and swelling
- Tenderness over the AC Joint
- A visible bump above the shoulder
- pain with lying on the involved side
- Loss of shoulder motion
- Loss of shoulder strength
- “Popping,” “clicking,” or “catching” sensation with movement of the shoulder
- Discomfort with normal daily activities that stress the AC Joint, such as lifting objects overhead, reaching across your body, or carrying heavy objects at your side
HOW IS AN AC JOINT INJURY DIAGNOSED?
Diagnosis of an AC Joint injury starts with a thorough review of the client’s medical history, including specifics such as onset of symptoms, aggravating factors, and any remedies that provide relief. Your Physical Therapist should examine your shoulder and assess various areas such as range of motion, strength, joint mobility, tenderness, sensation, and swelling. Other nearby areas such as the neck and upper back should also be screened to determine whether or not they are also contributing to your AC Joint condition. In more severe cases an X-ray or MRI may be indicated to determine the severity of the injury.
HOW CAN PHYSICAL THERAPY HELP TREAT AN AC JOINT INJURY?
Once an AC Joint injury has been diagnosed, your Physical Therapist should work with you to develop an individualized plan tailored to your specific shoulder condition and goals. Some of the more effective treatments may include:
MANUAL THERAPY–Your Physical Therapist will gently move and mobilize your shoulder joint and surrounding soft tissue to improve mobility, flexibility, and strength. These techniques are especially helpful to target areas that one is having difficulty with trying to treat on their own.
RANGE OF MOTION–Whether from trauma or overuse, an injury to the AC Joint can cause the joint to be irritated, often resulting in pain, swelling, and stiffness, leading to loss of normal motion. Motions most painful with this type of injury includes reaching overhead or across your body. One important factor in the healing process is to avoid excess stress on the healing joint. Your Physical Therapist should establish a plan that will balance joint protection and motion restoration.
STRENGTH TRAINING–After an injury, muscles surrounding the AC Joint tend to get weak from lack of normal use. These include muscles not only of the shoulder but of the shoulder blade, upper back, and elbow as well. Therefore, addressing the strength of all aforementioned muscle groups is crucial to making sure the AC Joint is protected and moving efficiently. Your Physical Therapist should design an individualized exercise program tailored specifically to you to strengthen the muscles at and around the AC Joint.
FUNCTIONAL TRAINING–The AC Joint is often asked to bear a significant load for such a relatively small joint. In order to meet this demand successfully, you may need to retrain your entire shoulder to work optimally in different positions. As experts in assessing movement quality, your Physical Therapist should be able to point out and correct your movements to help you maintain a pain free shoulder.
EDUCATION–The first step to addressing your shoulder pain is generally rest. However, the amount of rest varies with the degree of your injury. Your Physical Therapist should create a personalized plan for your rehabilitation so you can safely return to your necessary daily activities and desired recreational activities.
CAN AN AC JOINT INJURY BE PREVENTED?
While it may obviously be difficult to prevent many TRAUMATIC AC Joint injuries like bicycle crashes and falls to the ground, since accidents do happen, still much can be done to prevent certain events that lead to OVERUSE injuries of the AC Joint, including:
- Avoiding repetitive overhead lifting when possible
- Monitoring work and weightlifting activities, particularly repetitive overhead lifting
- Learning about the risks of pushing through pain
- Maintaining adequate general overall shoulder strength and mobility to safely and efficiently perform desired tasks
- Consulting with a Physical Therapist if symptoms are persistent or worsening despite rest