AC Joint Pain (Sprain & Osteoarthritis)

Overview

The acromioclavicular (AC) joint is the small joint on the very top of your shoulder, where the outer end of the collarbone meets the bony tip of the shoulder blade. You can feel it as a slight bump. It allows the shoulder blade to move with the collarbone when you lift your arm, and it takes a lot of load when you press weights or land on your shoulder.

AC joint pain comes in two main forms. An AC joint sprain (sometimes called a separated shoulder) happens when the ligaments holding the joint together are stretched or torn, usually by falling directly onto the point of the shoulder — common in cycling, rugby, football and skiing. Sprains are graded from mild (ligaments stretched) to severe (joint visibly displaced).

AC joint osteoarthritis is wear of the joint cartilage over time, often seen in people over 40 who have done years of weight training, manual work or overhead sport. The joint becomes stiff and sore, and a small bony bump may develop on top of the shoulder.

Both types cause pain that is very localised to the top of the shoulder and is aggravated by reaching across the body, bench press and lying on that side.

Causes and risk factors

• A fall onto the point of the shoulder (cycling, contact sports, skiing)
• Heavy bench press, dips and overhead pressing
• Years of manual work or weight training
• Age over 40 (osteoarthritis)
• A previous AC joint sprain, which can lead to later arthritis
• Carrying heavy backpacks or loads on one shoulder

How we may be able to help

We assess the joint with specific tests that reproduce AC joint pain and distinguish it from rotator cuff problems, which often sit nearby. After a fall, if we suspect a higher-grade sprain or a fracture of the collarbone, we can arrange an online GP consultation for an X-ray and, if needed, a specialist referral.

For mild to moderate sprains, physiotherapy guides the joint through its recovery: initial protection and taping to support the joint, then progressive strengthening of the muscles that stabilise the shoulder blade and collarbone, and a gradual return to pressing and sport. Kinesiology taping can be particularly useful in the early weeks to reduce the drag on the healing ligaments.

For AC joint osteoarthritis, the aim is management rather than reversal. Joint mobilisation and soft tissue techniques such as IASTM or cupping for the surrounding muscles may reduce pain, and a tailored strength programme helps the shoulder share load more evenly. Therapeutic ultrasound and interferential therapy can provide pain relief during flares. Our chiropractor can address stiffness in the neck and upper back that often accompanies a sore AC joint. Where pain is persistent, we can arrange a specialist opinion.

What you can do at home

• After a fall, ice the top of the shoulder for 10–15 minutes several times a day for the first couple of days
• Avoid bench press, dips and heavy overhead work until the joint is assessed
• Avoid reaching across your body to the opposite shoulder, which compresses the joint
• Sleep on your back or the unaffected side
• Carry bags on the other shoulder, or use a rucksack with both straps
• For arthritis, keep the shoulder moving gently every day rather than resting it