AC Joint Injury


What Is an AC Joint Injury?

The acromioclavicular (AC) joint is where the collarbone (clavicle) meets the highest point of the shoulder blade (acromion). An AC joint injury, often called an AC separation, occurs when the ligaments that stabilize this joint are overstretched or torn—commonly from a fall onto the shoulder or direct impact.

These injuries range from mild sprains to complete separations, and they’re common in athletes, active individuals, and anyone who falls onto an outstretched arm or the shoulder itself.

Common Causes

  • Falling directly onto the shoulder

  • Sports contact (football, hockey, cycling crashes)

  • Slips and falls

  • Direct blow during lifting or overhead activity

Symptoms You May Notice

  • Pain at the top of the shoulder

  • Tenderness over the AC joint

  • Swelling or bruising

  • Pain with reaching across your body or overhead

  • Shoulder weakness or instability

  • A visible “bump” at the top of the shoulder (with more significant separations)

Grades of AC Joint Injury (Simplified)

  • Grade I – Mild sprain, ligaments stretched but intact

  • Grade II – Partial ligament tear, mild separation

  • Grade III – Complete ligament tear, visible bump

  • Grade IV–VI – Severe displacement (less common, often surgical)

Most Grade I–III injuries are treated conservatively and recover well with proper care and rehab.

Conservative Care & Recovery Timeline

Many AC joint injuries heal without surgery. A structured plan typically includes:

  • Reducing inflammation and pain

  • Restoring shoulder motion

  • Rebuilding strength and stability

  • Gradual return to activity

Recovery time varies:

  • Mild injuries: 2–4 weeks

  • Moderate injuries: 6–12 weeks

  • More severe injuries: 3–6 months

AC Joint Rehab Protocol

Phase 1: Calm It Down (Days 1–7)

Goals: Reduce pain and inflammation, protect the joint

  • Ice 15–20 minutes, 2–3× daily

  • Avoid heavy lifting and overhead motions

  • Use a sling briefly if recommended

  • Gentle pain-free shoulder movements only

Simple Movements

  • Shoulder rolls (small, slow circles)

  • Pendulum swings (arm relaxed, small arcs)

Phase 2: Restore Motion (Weeks 1–3)

Goals: Regain range of motion without aggravation

  • Wall-assisted arm raises (pain-free range)

  • Cross-body stretch (gentle, no forcing)

  • Doorway chest stretch

Rule: Mild stretch is OK—sharp pain is not.

Phase 3: Strength & Stability (Weeks 3–6)

Goals: Build shoulder support and control

  • Resistance band rows

  • External rotations with band

  • Scapular squeezes

  • Modified push-ups (wall or incline)

Focus on slow, controlled movements and proper posture.

Phase 4: Return to Activity (Weeks 6+)

Goals: Resume normal life and sport safely

  • Progress to overhead strengthening

  • Sport-specific or work-specific movements

  • Gradual return to lifting, throwing, or contact activity

Your provider may guide this phase closely to prevent reinjury.

Seek Evaluation

You should get evaluated if:

  • Pain persists beyond expected healing time

  • Shoulder feels unstable or “slips”

  • Strength doesn’t return

  • Daily activities remain painful

  • There’s a large deformity or worsening symptoms

Early evaluation helps prevent chronic shoulder dysfunction.

Long-Term Outlook

Most people recover fully from an AC joint injury with proper care and rehab. Even when a small bump remains, function and strength can return to normal. The key is addressing shoulder mechanics, posture, and stability—not just waiting for pain to disappear.

Takeaway

An AC joint separation may look alarming, but with the right plan, most patients heal well and return to the activities they love. Consistency with rehab and smart progression matter more than rushing back too soon.