Physical Therapist's Guide to
Acromioclavicular Joint (AC Joint) Injuries
Acromioclavicular (AC) joint injury is a term used to describe an injury to the top of the shoulder, where the front of the shoulder blade (acromion) attaches to the collarbone (clavicle). It can be caused by a traumatic event, such as a fall directly on the outside of the shoulder, or by repetitive overuse. AC joint injuries are most common in individuals younger than 35 years of age, with males sustaining 5 times more traumatic AC joint injuries than females. Because younger athletes are most likely to participate in high-risk and collision activities, such as football, biking, snow sports, hockey, and rugby traumatic AC joint injuries occur most often in this population. AC joint injuries can be identified and effectively treated by a physical therapist, often avoiding the need for surgery.
What Are Acromicioclavicular (AC) Joint Injuries?
There are 4 ligaments holding the 2 bones of the AC joint (the acromion and the clavicle) together. When an AC joint injury occurs, these ligaments are stressed, resulting in 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 occurs when there is a disruption of the joint due to damaged ligaments holding the 2 bones of the joint together. This injury is called a shoulder separation (in contrast to a shoulder dislocation, it involves the ball-and-socket joint of the shoulder).
Traumatic AC joint injuries are most common in individuals who sustain a fall and land on the outside of the shoulder or onto a hand (eg, a football player who is tackled, a bicyclist who crashes, or a manual laborer who falls off a ladder.
Traumatic AC joint injuries are graded from mild to severe based on the amount of separation of the joint. Treatment of mild cases likely will be provided by a physical therapist; more severe cases may require surgery followed by physical therapy.
An overuse AC joint injury occurs over time as repeated, excessive stress is placed on the joint. Cartilage at the ends of the acromion and clavicle bones protects the joint from daily wear and tear. Over time, the demand placed on this cartilage may be more than it is capable of enduring, resulting in an overuse injury. Significant wearing of the cartilage is known as arthritis. Overuse AC joint injury is most common in individuals who perform tasks, such as heavy weight lifting (bench and military presses), or jobs that require physical labor with the arms stretched over the head.
How Does it Feel?
With an AC joint injury, you may experience:
- General shoulder pain and swelling
- Swelling and tenderness over the AC joint
- Loss of shoulder strength
- A visible bump above the shoulder
- Pain when lying on the involved side
- Loss of shoulder motion
- A popping sound or catching sensation with movement of the shoulder
- Discomfort with daily activities that stress the AC joint, like lifting objects overhead, reaching across your body, or carrying heavy objects at your side
How Is It Diagnosed?
Diagnosis of an AC joint injury starts with a thorough review of the patient’s medical history, including specific questions regarding when the pain began, and what aggravates and relieves the pain.
Your physical therapist will examine your shoulder and assess different measures, such as sensation, motion, strength, flexibility, tenderness, and swelling. Your physical therapist will perform several tests specific to the shoulder joint to examine the structures located there. The therapist may also ask you to briefly demonstrate the activities or positions that cause your pain. Other nearby areas, such as your neck and upper back will also be examined to determine whether they, too, might be contributing to your shoulder condition.
While an AC joint injury can usually be identified through a shoulder examination, diagnostic imaging, such as ultrasound, x-ray, or MRI is often used to confirm the diagnosis and determine the severity of the injury.
How Can a Physical Therapist Help?
Once other conditions have been ruled out and an injury to the AC joint is diagnosed, your physical therapist will work with you to develop an individualized plan tailored to your specific shoulder condition and your goals. There are many physical therapy treatments that have been shown to be effective in treating this condition. Your physical therapist may focus on:
Range of Motion. An injury to the AC joint, whether traumatic or overuse, causes the joint to be irritated, often resulting in swelling and stiffness, causing loss of normal motion. Motions that are usually most difficult after an AC joint injury are reaching across your body and lifting your arm directly overhead. While it is important to regain your normal shoulder motion, it is also important to allow your injury to heal without placing excessive stress on the healing joint. Your physical therapist will assess your motion and the degree of your injury, and establish a plan that will balance joint protection and motion restoration.
Strength Training. After an injury, the surrounding muscles demonstrate weakness. All of the muscles near the shoulder and elbow as well as those of the upper back, work together to allow for normal, coordinated upper-body motion. Therefore, balancing the strength of all the upper-body muscles is crucial to making sure the shoulder joint is protected and moves efficiently. Your physical therapist will design an individualized exercise program to strengthen the muscles at and around the shoulder, so that each muscle is able to properly perform its job.
Manual Therapy.Physical therapists are trained in manual (hands-on) therapy. If needed, your physical therapist will gently move and mobilize your shoulder joint and surrounding muscles as needed to improve their motion, flexibility, and strength. These techniques can target areas that are difficult to treat on your own.
Pain Management.Your physical therapist may recommend therapeutic modalities, such as ice and heat to aid in pain management.
Functional Training. The AC joint is a relatively small joint that is often asked to bear a significant load. In order to successfully meet this demand, there is a need for functional training, teaching your entire shoulder to work best in different positions. For example, when lifting overhead, poor coordination places undue stress on the shoulder. Physical therapists are experts in assessing movement quality. Your physical therapist will 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 rest. The amount of rest required varies, and largely depends on the degree of your injury. Your physical therapist will create a personalized plan for your rehabilitation, so you can safely return to your desired daily and recreational activities.
Can this Injury or Condition be Prevented?
It may be difficult to prevent many traumatic AC joint injuries, such as bicycle crashes, falls to the ground, etc. Accidents do happen. Fortunately, however, much can be done to prevent the cascade of events that lead to overuse injuries to the AC joint, including:
- Learning about the risks of pushing through pain.
- Monitoring work and weight-lifting activities, particularly repetitive overhead lifting.
- Avoiding repetitive overhead lifting when possible.
- Maintaining adequate general shoulder strength and motion to safely perform desired tasks.
- Consulting with a physical therapist if symptoms are persistent or worsening despite rest.
Real Life Experiences
Noah is a 17-year-old varsity starting quarterback. In his first regular season game, he injured his left, nonthrowing shoulder when he was tackled and landed directly on it. Noah was unable to continue to play during that game. He was immediately evaluated by the team athletic trainer and physician on the sideline, who placed Noah in a sling and ordered an x-ray. Fortunately, Noah's x-rays revealed no fracture had occurred, and Noah was referred to physical therapy.
Noah's physical therapist took his health history and performed a thorough examination. He asked Noah about his goals and specific sport and position demands. The physical examination revealed that Noah’s AC joint was very tender and swollen, and that he had lost significant motion and strength in his shoulder.
Together, Noah, his physical therapist, parents, and coach developed a treatment plan to help get him back on the field in 4 to 6 weeks. Noah's first treatment was to keep wearing the sling to give his damaged shoulder ligaments a chance to heal. During this initial phase, Noah could not participate in any football activities, but did work regularly with his physical therapist on selective, gentle, stretching and strengthening exercises.
After about 2 weeks when his shoulder was less tender and he had met some of the goals set in physical therapy, Noah began some higher-intensity strengthening exercises with his physical therapist, and was allowed to resume conditioning with his team under his coach's watchful eye. The following week, Noah continued to achieve his physical therapy goals and was allowed to participate in noncontact football activities, while continuing to work with his physical therapist on advanced strengthening drills.
After 5 weeks of physical therapy, Noah achieved all of the return-to-sport goals that his physical therapist had established, and was cleared to return to play by his physical therapist, team physician, and athletic trainer. Noah was thrilled that all of his hard work had paid off, and he returned to the field, pain-free, for the all-important homecoming game!
What Kind of Physical Therapist Do I Need?
All physical therapists are prepared through education and clinical experience to treat a variety of conditions or injuries. You may want to consider:
- A physical therapist who is experienced in treating people with orthopedic or musculoskeletal injuries.
- A physical therapist who is a board-certified specialist or who has completed a residency in orthopedic or sports physical therapy, as they will have advanced knowledge, experience, and skills that apply to an active population.
You can find physical therapists who have these and other credentials by using Find a PT, the online tool built by the American Physical Therapy Association to help you search for physical therapists with specific clinical expertise in your geographic area.
General tips when you're looking for a physical therapist (or any other health care provider):
- Get recommendations from family and friends or from other health care providers.
- When you contact a physical therapy clinic for an appointment, ask about the physical therapists' experience in helping patients with shoulder pain.
- During your first visit with the physical therapist, be prepared to describe your symptoms in as much detail as possible, and report activities and movements that make your symptoms worse.
The American Physical Therapy Association (APTA) believes that consumers should have access to information that could help them make health care decisions, and also prepare them for their visit with their health care provider.
The following articles provide some of the best scientific evidence related to physical therapy treatment of acromioclavicular joint injuries. The articles report recent research and give an overview of the standards of practice both in the United States and internationally. The article titles are linked either to a PubMed* abstract of the article or to free full text, so that you can read it or print out a copy to bring with you to your health care provider.
Mall NA, Foley E, Chalmers PN, Cole BJ, Romeo AA, Bach BR Jr. Degenerative joint disease of the acromioclavicular joint: a review. Am J Sports Med. 2013;41(22):2684-2692. Article Summary in PubMed.
Pallis M, Cameron KL, Svoboda SJ, Owens BD. Epidemiology of acromioclavicular joint injury in young athletes. Am J Sports Med. 2012;40(9):2072-2077. Article Summary in PubMed.
Cote MP, Wojcik KE, Gomlinski G, Mazzocca AD. Rehabilitation of acromioclavicular joint separations: operative and nonoperative considerations. Clin Sports Med. 2010;29(2):213-228. Article Summary in PubMed.
*PubMed is a free online resource developed by the National Center for Biotechnology Information (NCBI). PubMed contains millions of citations to biomedical literature, including citations in the National Library of Medicine's MEDLINE database.
Authored by Allison Mumbleau, PT, DPT, board-certified clinical specialist in sports physical therapy. Reviewed by the editorial board.