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AC Joint Injury: Symptoms, Causes & Treatment

A sudden impact to the shoulder can leave you with significant discomfort. One common source is an AC joint injury. Understanding what happens during this type of injury is the first step toward recovery.

What Is an AC Joint Injury?

The acromioclavicular (AC) joint sits at the top of your shoulder. It connects your collarbone (clavicle) to the highest point of your shoulder blade (acromion). Strong ligaments hold these bones together, providing stability when you lift your arms or carry heavy objects.

An AC joint injury occurs when these ligaments stretch or tear — often referred to as a shoulder separation. Depending on the force of the impact, the injury can range from a mild sprain to a complete tear in which the collarbone separates from the shoulder blade.

Symptoms

The severity of your symptoms generally reflects the extent of ligament damage.

  • —Shoulder pain — A sharp, immediate pain at the top of the shoulder.
  • —Swelling and bruising — The injured area may swell quickly and develop bruising over the following days.
  • —Limited arm movement — Lifting your arm overhead or reaching across your body often triggers intense pain.
  • —Visible bump — In severe cases, the collarbone may shift upward, creating a distinct bump at the top of the shoulder.
  • —Weakness — The shoulder may feel unstable or weak, making it difficult to lift everyday objects.

Common Causes

An AC joint injury typically results from a direct blow to the top of the shoulder. The force drives the shoulder blade downward while the collarbone remains in place, tearing the connecting ligaments.

  • —Falls — Landing directly on the point of the shoulder is the most frequent cause.
  • —Sports injuries — Contact sports such as football, rugby, and hockey carry a high risk. Cyclists are also commonly affected after falls.
  • —Car accidents — The blunt force of a vehicle collision can easily separate the shoulder joint.
  • —Direct trauma — Any heavy impact to the top of the shoulder can stretch or tear the AC ligaments.

How It Is Diagnosed

An orthopaedic specialist will begin with a thorough physical examination — checking for tenderness, swelling, and deformity, and asking you to move your arm to assess range of motion.

  • —X-rays — Reveal the position of the collarbone and indicate whether the bones have separated. Your doctor may ask you to hold a weight to make a subtle separation more visible.
  • —MRI — Used when additional damage to soft tissues, cartilage, or the rotator cuff is suspected.

Treatment Options

Treatment depends on the severity of the separation, graded from mild (Grade 1) to severe (Grades 4–6). Most mild to moderate injuries respond well to non-surgical treatment.

  • —Rest — Avoid heavy lifting and overhead reaching until pain settles.
  • —Ice — Apply ice packs for 20 minutes several times a day to reduce swelling and ease pain.
  • —Medications — Over-the-counter anti-inflammatory pain relievers such as ibuprofen help manage discomfort.
  • —Injections — A corticosteroid injection may be recommended for persistent or severe inflammation.
  • —Surgery — Reserved for serious injuries causing significant deformity or where the collarbone pierces surrounding muscle tissue.

Physiotherapy

Rehabilitation is a critical part of recovery. A physical therapist will guide you through exercises to restore full shoulder function without placing excessive strain on the healing ligaments.

  • —Restore motion — Gentle pendulum exercises and stretches prevent the joint from stiffening during healing.
  • —Strengthen muscles — As pain subsides, resistance exercises rebuild the muscles supporting the shoulder blade and collarbone.
  • —Reduce stiffness — Manual therapy and targeted stretching relieve tension in the neck and upper back.

Using a Sling

A sling supports the weight of your arm and relieves pressure on the healing ligaments. Your doctor will advise how long to wear it — from a few days for mild sprains to several weeks for more severe separations. Remove the sling periodically to perform gentle elbow and wrist movements to prevent stiffness from developing.

Recovery Time

Mild Injury Return to most activities within 2 to 6 weeks.
Moderate to Severe Recovery can take several months, particularly for those whose work involves heavy or overhead activity.
After Surgery Structured rehabilitation lasting 4 to 6 months before clearance for high-impact activity.

When to See a Specialist

Schedule an appointment if you experience any of the following.

  • —A visible bump or deformity at the top of the shoulder
  • —Severe pain that does not improve with ice and over-the-counter medication
  • —Inability to lift your arm or carry light objects
  • —Numbness or tingling travelling down the arm
  • —A feeling of looseness or instability in the shoulder

Frequently Asked Questions

1How long does an AC joint injury take to heal?
Mild injuries often resolve within two to six weeks. Severe injuries may require several months of recovery and rehabilitation.
2Can it heal without surgery?
Yes. Most mild to moderate injuries improve with rest, ice, a sling, and physical therapy. Surgery is only considered for severe grades of injury.
3Is physical therapy necessary?
Strongly recommended. It improves shoulder strength, restores mobility, and helps prevent long-term stiffness and complications.
4Should I wear a sling?
A sling reduces pain and protects the joint during early healing. Your doctor will advise the appropriate duration based on injury severity.
5What does an AC joint injury feel like?
Sharp pain at the top of the shoulder, swelling, and discomfort when lifting the arm or reaching across the chest. A visible bump may be present in severe cases.

Get Expert Shoulder Care

An accurate diagnosis and an individualised treatment plan are essential for a smooth recovery. Schedule an evaluation with an experienced orthopaedic specialist today.

Dr. Hasan Syed, MD — Orthopaedic Specialist