Overview
An acromioclavicular joint sprain is an injury to the AC joint, the small joint at the top of the shoulder where the collarbone (clavicle) meets the highest part of the shoulder blade (acromion). Most sprains involve stretching or partial tearing of the AC joint ligaments, which can irritate the joint and surrounding tissue. Pain and tenderness often increase when you move your arm across your body or lift it overhead. In more severe cases, the joint may feel unstable and appear more prominent at the injury site.
Symptoms
Pain is usually felt on the very top of the shoulder near the AC joint, and it may worsen with reaching, pushing, pulling, or raising the arm. Many people notice tenderness when they press over the joint, along with swelling and bruising after a fall or direct impact. Some develop pain with cross-body movements such as fastening a seatbelt. Depending on severity, strength may feel reduced because using the arm becomes uncomfortable, but true numbness is not typical for a simple sprain.
Causes
AC joint sprains commonly occur after a direct blow to the top of the shoulder, such as from a fall, sports contact, or a collision. The impact can stretch the stabilizing ligaments, leading to inflammation and pain. Less commonly, a sudden twisting force through the shoulder can overload these ligaments even without an obvious direct hit.
Risk Factors
Risk is higher in contact sports and activities with frequent falls, such as football, hockey, rugby, skiing, cycling, and martial arts. Poor balance, inadequate conditioning, and lack of shoulder strength or control can make injuries more likely during slips or collisions. Having prior AC joint injury may also increase the likelihood of reinjury because the tissues can remain vulnerable during the return to activity.
Prevention
You can reduce risk by strengthening the muscles that support the shoulder blade and shoulder, including the rotator cuff and upper back, and by improving overall balance and landing mechanics. Using proper technique and protective gear in higher-risk sports can lower the chance of a direct shoulder impact. Gradually increasing training intensity and avoiding sudden spikes in overhead or heavy-contact activity can also help protect the AC joint.
How the Diagnosis Is Evaluated
Clinicians usually start with a detailed history about how the injury happened and what movements worsen the pain. A physical exam focuses on tenderness over the AC joint, pain with cross-body adduction, and assessing shoulder motion and stability. Imaging is often used to confirm diagnosis and rule out fractures; plain X-rays can show joint alignment, and additional imaging is sometimes ordered if symptoms persist or the injury severity is unclear. Not every patient needs advanced imaging.
Nonsurgical Treatment Options
Early care typically includes relative rest, activity modification, and pain control with ice or heat and over-the-counter anti-inflammatory medication if safe for you. A short period of sling use may reduce discomfort, but prolonged immobilization is usually avoided to prevent stiffness. Physical therapy helps restore pain-free range of motion and gradually rebuild shoulder and scapular strength using controlled exercises. Supportive taping or bracing can reduce AC joint stress during daily activities and sport. If pain remains significant despite conservative care, a clinician may consider a corticosteroid injection for targeted pain relief; platelet-rich plasma (PRP) or other biologic injections are sometimes discussed for persistent symptoms, though they are not first-line for a typical sprain.
When to Seek Medical Attention
Seek prompt medical evaluation if you have significant deformity over the AC joint, rapidly worsening swelling or bruising, or you cannot lift your arm due to pain or weakness. Get urgent care if you develop numbness or tingling down the arm, severe or uncontrolled pain, or signs of infection such as fever. Contact a clinician soon if symptoms do not improve after a brief period of conservative care or if you cannot return to normal daily activities. If you had major trauma or suspect a fracture, evaluation should not be delayed.
Frequently Asked Questions
It usually causes pain and tenderness right on top of the shoulder at the AC joint, often worse with reaching across your body or lifting your arm.
Many mild sprains improve within a few weeks with conservative care, while more significant injuries can take longer and may require structured physical therapy.
Next Steps
If you have pain on the top of your shoulder after a fall or direct impact, limit painful movements and consider an in-person assessment to confirm the diagnosis and injury severity. If symptoms are not clearly improving within 1 to 2 weeks, or if you notice deformity, instability, or numbness, seek evaluation sooner. A clinician can guide a safe return to activity and help you start the right rehabilitation exercises.