The AC joint, short for acromioclavicular joint, sits at the top of the shoulder where the collarbone meets a part of the shoulder blade called the acromion. It is held together by a capsule and several ligaments, and it helps position the shoulder and control its motion and strength. When those ligaments are sprained or torn, the joint becomes unstable and painful, and shoulder function suffers.

AC joint problems are among the most common reasons people seek care after a shoulder injury, yet they are frequently overlooked because attention tends to focus on other shoulder structures (J Clin Med, 2024; PMID 38592250). Knowing how these injuries happen and what helps them recover can save weeks of frustration.

What Causes AC Joint Pain

There are two main routes to AC joint pain. The first is sudden trauma, most often a fall directly onto the shoulder or the outside of the upper arm, which is common in contact sports and cycling. The second is gradual overload from repeated overhead lifting or pressing with poor mechanics, which can also lead to arthritis in the joint over time.

A fall onto the point of the shoulder
Direct impact during contact sports
Repeated heavy lifting or overhead work with poor form
Long-term wear that leads to AC joint arthritis

Grading and Classification

Ligament injuries are generally graded by how much tissue is damaged: a grade 1 is a mild sprain with no torn fibers, grade 2 involves partial tearing, and grade 3 is a complete rupture. Clinicians also use the Rockwood classification, which ranges from a minor sprain with the joint still aligned, through partial and complete ligament disruption, to more severe displacements. The grade guides whether conservative care or, in higher grades, a surgical opinion is appropriate.

Common Symptoms

Pain and swelling localized to the top of the shoulder
Tenderness directly over the AC joint
Pain with bench pressing, dips, or reaching across the body
Discomfort when lying on the affected side at night
Painful or limited range of motion, especially raising the arm out to the side

What the Evidence Says About Treatment

Most low-grade AC joint injuries (types 1 and 2) recover well with conservative care, while the management of higher grades is more individualized and may involve a surgical opinion. Current clinical practice guidelines for shoulder disorders emphasize accurate diagnosis followed by structured rehabilitation for the majority of cases (Arch Phys Med Rehabil, 2024; PMID 37832814; J Clin Med, 2024; PMID 38592250).

Early management focuses on settling pain and protecting the joint, followed by a graded return of motion and strength. Recovery timelines vary widely, from about one to ten weeks depending on severity and demands, with higher-grade injuries taking longer.

Rehabilitation Exercises

Rehabilitation usually progresses from gentle assisted motion to active movement and then loading. A typical early-stage routine includes:

Pendulum swings: lean forward, let the arm hang, and make small relaxed circles to ease tension without forcing the joint
Assisted flexion: use the opposite hand or a light dowel to gently guide the arm forward through a comfortable range
Seated table slides: rest the hand on a towel and slide it forward while leaning the trunk, gradually increasing reach
Scapular and rotator cuff strengthening once pain allows, to restore shoulder control

Progress should be guided by symptoms. Movements should stay within a comfortable range early on, with load added gradually as the joint settles.

When to Seek Care

See a professional if you had a significant fall or impact, if the joint looks deformed or noticeably stepped up, or if pain and weakness are not improving with sensible self-management. A hands-on assessment can confirm the grade of injury, rule out other shoulder problems, and build a rehabilitation plan suited to your goals. At Family Health Chiropractic in Austin, care focuses on restoring pain-free motion and rebuilding strength so you can return to your activities with confidence.