AC Joint Inflammation
The shoulder is a complex, ball-and-socket joint made up of three bones: the upper arm bone (humerus), shoulder blade (scapula), and collarbone (clavicle). The ball, or head, of the upper arm bone fits into a rounded socket (glenoid) in the shoulder blade. The arm bone is kept centered in the shoulder socket by a combination of muscles and tendons (rotator cuff). The rotator cuff covers the head of the upper arm bone and attaches it to the shoulder blade.
The AC (acromioclavicular) joint is formed where a portion of the scapula (acromion) and the clavicle meet and are held together by tough tissues (ligaments) that act like tethers to keep the bones in place.
Inflammation is the body's natural response to injury, disease, overuse or degeneration and it often causes swelling, pain or irritation. Inflammation of the AC joint is a frequent cause of pain in the top portion of the shoulder.
- Osteoarthritis—Also known as "wear-and-tear" arthritis, osteoarthritis destroys the articular cartilage (smooth outer covering of bone), resulting in inflammation. As the cartilage wears away and becomes frayed and rough, the protective space between the bones decreases. During movement, the bones of the joint rub against each other and cause pain. Osteoarthritis usually affects people over 50 years of age. Posttraumatic arthritis is a form of osteoarthritis that develops after an injury, such as a fracture or dislocation of the shoulder.
- Overuse—Pain in the AC joint is often caused by heavy, overhead use of the shoulder. In weight lifters, this is a very common source of pain because frequent bench pressing and other lifting activities can lead to inflammation and dissolving of the end of the collar bone (distal clavicle) where it meets the shoulder blade (acromion) at the AC joint.
AC joint inflammation causes pain on the top of the shoulder, at the point where the collarbone (clavicle) meets the highest point of the shoulder blade (acromion). Pain may radiate to the lower part of the side of the neck or ear. Sleeping on the involved shoulder can cause pain, as can overhead use of the arm or reaching across the body.
After discussing your symptoms and medical history, your physician will conduct an examination to assess pain, instability or other problems in your shoulder. Additional imaging tests, such as X-rays or an MRI are frequently helpful in confirming the diagnosis.
- X-rays—Although X-rays do not show soft tissues, these images may be used to reveal any injuries to the bones in the shoulder.
- Magnetic resonance imaging (MRI)—By providing detailed images of soft tissues, an MRI may reveal inflammation in the AC joint and may also help your doctor identify any injuries to the ligaments and tendons surrounding your shoulder joint.
One or more nonsurgical options may be prescribed to provide relief from inflammation and resulting pain.
- Activity modification—Your doctor may first recommend simply modifying your daily routine and avoiding activities that cause or aggravate symptoms.
- Nonsteroidal anti-inflammatory medication (NSAIDs)—Drugs such as ibuprofen or naproxen may help relieve pain, inflammation and swelling. Most people are familiar with nonprescription NSAIDs such as aspirin and ibuprofen, however, whether using over-the-counter or prescription strength, they must be taken carefully. Using these medications for more than one month should be reviewed with your primary care physician. If you develop acid reflux or stomach pains while taking an anti-inflammatory, be sure to talk to your doctor.
- Steroid-based injections—Steroids are powerful anti-inflammatories that can help decrease pain and inflammation in the joint. Many patients experience short-term relief from these injections, however they typically do not provide a cure and the discomfort often returns with time. On average, cortisone injections last for 2-3 months. Ultrasound guidance may be used to ensure that successful placement of the steroid into the small space of the AC joint. Although less invasive than surgery, steroid-based injections are usually prescribed only after a medical evaluation. Discuss the risks and benefits with your physician.
- Arthroscopy—This minimally invasive procedure requires only small incisions and is often done on an outpatient basis. Your orthopaedic surgeon will view the inside of the shoulder with a tiny camera and perform the arthroscopic surgery using special, pencil-thin instruments. For AC joint pain, a small bur is used for removal of bone spurs and diseased bone in the joint to prevent the ends of the bone from grinding together.
- Risks and complications—With any surgery, there are some risks, and these vary from person to person. Complications are typically minor, treatable and unlikely to affect your final outcome. Your orthopaedic surgeon will speak to you prior to surgery to explain any potential risks and complications that may be associated with your procedure.
- Rehabilitation—Immediately following surgery, a sling may be used to temporarily immobilize the shoulder. Once the sling has been removed, an exercise program will be prescribed to facilitate range of motion in the shoulder and prevent scarring as the ligaments heal. As rehabilitation progresses, exercises to strengthen the shoulder will be gradually added. Rehabilitation and your commitment to following your prescribed plan of treatment will play a very important role in helping you resume everyday activities. Your surgeon will tell you when you can return to work, driving and normal daily functions.