Managing Subacromial Impingement in the Shoulder

Subacromial impingement, a common source of shoulder pain, has been recognized since the 19th century, with significant contributions to its understanding from orthopedic surgeon Charles Neer in the 1970s. Neer described it as a mechanical compression of structures in the subacromial space, leading to pain and dysfunction. This condition occurs when the space between the acromion (part of the shoulder blade) and the humeral head narrows, pinching structures like the rotator cuff tendons, subacromial bursa, or biceps tendon. This blog post explores the causes, triggers, and mechanisms behind subacromial impingement, alongside a comprehensive guide to its management, including identifying affected structures, when to seek imaging or injections, recommended exercises, activities to avoid, and tips for comfortable sleeping positions.

Causes and Triggers of Subacromial Impingement

What Causes It?

Subacromial impingement can result from a combination of anatomical, biomechanical, and lifestyle factors:

• Anatomical Factors:

  • Acromial Shape: A hooked or curved acromion (Type II or III) reduces subacromial space, increasing compression risk.

  • Bone Spurs: Osteophytes from aging or arthritis can narrow the subacromial space.

  • Joint Instability: Lax ligaments or labral tears can cause abnormal shoulder movement, leading to impingement.

• Biomechanical Factors:

  • Rotator Cuff Weakness: Weak rotator cuff muscles fail to stabilize the humeral head, allowing it to migrate upward and compress structures.

  • Poor Posture: Forward head posture or rounded shoulders reduces subacromial space.

  • Scapular Dyskinesis: Abnormal shoulder blade movement disrupts shoulder mechanics.

• Lifestyle and Occupational Factors:

  • Repetitive Overhead Activities: Sports (e.g., swimming, tennis) or jobs (e.g., painting, construction) stress the shoulder.

  • Trauma: Falls or direct shoulder injuries can damage tissues, initiating impingement.

What Can Bring It On?

Certain activities or conditions can trigger or exacerbate symptoms:

• Sudden Overuse: A weekend of intense activity (e.g., painting a room or playing sports) can irritate the bursa or tendons.

• Poor Technique: Incorrect form during weightlifting or sports increases stress on shoulder structures.

• Inactivity: Prolonged immobility can lead to muscle weakness and tightness, contributing to impingement.

• Inflammation: Pre-existing bursitis or tendinitis can reduce subacromial space, worsening compression.

• Aging: Age-related tissue degeneration (e.g., tendon wear or bursa thickening) increases susceptibility.

Why It Happens?

Subacromial impingement occurs due to a mismatch between the subacromial space and the demands placed on it. The rotator cuff tendons and bursa require adequate clearance to glide smoothly during arm movements. When this space is compromised—whether by anatomical narrowing, muscle imbalance, or repetitive stress—these structures become compressed, leading to inflammation, pain, and potential tissue damage. Over time, untreated impingement can progress to rotator cuff tears or chronic bursitis.

Identifying Affected

Determining which structures are involved is key to effective management. Here’s how to assess potential culprits like the subacromial bursa or rotator cuff:

• Symptom Analysis:

  • Pain Location: Pain on the outer shoulder that worsens with overhead movements often points to the subacromial bursa or rotator cuff tendons. Pain radiating down the arm may suggest nerve involvement or biceps tendon issues.

  • Night Pain: Difficulty sleeping on the affected side is common with bursitis or rotator cuff inflammation.

  • Weakness: Weakness during arm elevation or rotation may indicate rotator cuff tendon involvement.

• Physical Tests (Consult a healthcare provider for accurate assessment):

  • Neer’s Test: Pain when the arm is raised forward suggests impingement of the bursa or rotator cuff.

  • Hawkins-Kennedy Test: Pain during internal rotation with the arm at 90 degrees indicates possible bursa or tendon irritation.

  • Empty Can Test: Weakness or pain when resisting downward pressure with the arm in a thumbs-down position may point to supraspinatus (rotator cuff) involvement.

  • Yergason’s Test: Pain during resisted supination of the forearm can indicate biceps tendon involvement.

• Professional Evaluation:

  • A physiotherapist or doctor may use these tests to narrow down the affected structures. If symptoms persist, diagnostic imaging may be needed (see below).

When to Get an X-Ray or Injection

X-Ray

An X-ray is not always necessary but may be recommended in specific cases, your GP can guide this.

• Persistent Pain: If pain lasts more than 6–8 weeks despite conservative treatment.

• Suspected Structural Issues: To rule out bone-related causes like acromial spurs, arthritis, or calcific tendinitis.

• Trauma History: If there’s a history of shoulder injury that might involve fractures.

Note: X-rays don’t show soft tissues like the bursa or tendons well. Ultrasound or MRI may be used for these structures if needed.

Corticosteroid Injection

A corticosteroid injection into the subacromial space may be considered:

• When: If pain significantly limits daily activities or sleep and doesn’t improve after 4–6 weeks of conservative measures (e.g., rest, physiotherapy).

• Purpose: Reduces inflammation in the bursa or tendons, providing temporary relief to facilitate rehabilitation.

• Considerations: Injections are not a cure and should be paired with exercises. Repeated injections (more than 2–3 per year) may weaken tendons, so discuss risks with your doctor.

Always consult a healthcare provider to determine if imaging or injections are appropriate.

Exercises to Manage Subacromial Impingement

Exercise is a cornerstone of recovery, focusing on improving shoulder mobility, strength, and posture. Perform these under guidance from a physiotherapist to ensure proper form.

1. Pendulum Exercise (Mobility)

• Purpose: Gently mobilizes the shoulder to reduce stiffness.

• How:

  1. Lean forward, supporting yourself with your unaffected arm on a table.

  2. Let the affected arm hang relaxed.

  3. Gently swing the arm in small circles (clockwise and counterclockwise) for 1–2 minutes.

• Reps: 2–3 times daily.

2. Scapular Retraction (Posture)

• Purpose: Strengthens muscles that stabilize the shoulder blade, reducing impingement.

• How:

  1. Sit or stand with arms relaxed.

  2. Squeeze shoulder blades together without shrugging shoulders.

  3. Hold for 5 seconds, then relax.

• Reps: 10–15 reps, 2–3 sets daily.

3. External Rotation with Band (Rotator Cuff Strength)

• Purpose: Strengthens rotator cuff muscles (infraspinatus, teres minor) to improve shoulder stability.

• How:

  1. Secure a resistance band at waist height.

  2. Hold the band with the affected arm, elbow bent at 90 degrees, tucked by your side.

  3. Rotate your forearm outward, keeping the elbow pinned to your side.

  4. Slowly return to the starting position.

• Reps: 10–12 reps, 2–3 sets, 2–3 times per week.

4. Wall Angels (Mobility and Posture)

• Purpose: Improves shoulder flexibility and thoracic spine mobility.

• How:

  1. Stand with your back against a wall, feet 6 inches away, knees slightly bent.

  2. Press your lower back, shoulders, and head against the wall.

  3. Raise arms to a “W” shape, then slowly slide them up to a “Y” shape, keeping elbows and wrists in contact with the wall.

  4. Return to the “W” position.

• Reps: 8–10 reps, 2 sets daily.

Notes:

• Stop if any exercise causes sharp pain.

• Progress gradually, increasing resistance or reps as tolerated.

Activities to Avoid

To prevent worsening impingement, avoid:

• Overhead Movements: Activities like overhead lifting, throwing, or swimming strokes (e.g., freestyle) that compress the subacromial space.

• Heavy Lifting: Avoid lifting heavy weights, especially with poor form.

• Repetitive Motions: Tasks like painting or cleaning windows that involve repeated arm elevation.

• Poor Posture: Slouching or forward head posture narrows the subacromial space.

Modify activities where possible (e.g., use a step ladder to reduce overhead reaching).

Sleeping Position for Comfort

Sleeping with subacromial impingement can be challenging due to night pain. Try these strategies:

• Avoid Sleeping on the Affected Side: This compresses the bursa and tendons.

• Sleep on Your Back:

  • Place a pillow under the affected arm to keep it slightly elevated and supported.

  • This reduces pressure on the subacromial space.

• Sleep on the Unaffected Side:

  • Hug a pillow with the affected arm to keep it in a neutral position.

  • Ensure the shoulder isn’t rolled forward.

• Use Extra Pillows: Prop yourself up slightly with pillows to reduce strain on the shoulder.

• Firm Mattress: A supportive mattress helps maintain spinal alignment, reducing shoulder stress.

Additional Tips

• Ice or Heat: Apply ice for 15–20 minutes to reduce inflammation after activity. Use heat to relax muscles before exercises.

• Pain Relief: Over-the-counter medications like ibuprofen may help manage pain and inflammation (consult a doctor first).

• Physiotherapy: A tailored program from a physiotherapist can address specific weaknesses or movement issues.

• Patience: Recovery can take weeks to months. Consistent exercise and activity modification are key.

When to Seek Further Help

Consult a healthcare provider if:

• Pain worsens or persists beyond 6–8 weeks.

• You experience significant weakness or loss of motion.

• Symptoms include numbness, tingling, or radiating pain, suggesting nerve involvement.

Conclusion

Subacromial impingement, caused by anatomical, biomechanical, or lifestyle factors, can be triggered by overuse, poor posture, or injury. Understanding its mechanisms allows for targeted management through exercises, activity modification, and optimized sleep positions. With consistent effort and professional guidance, most people can reduce pain and regain shoulder function. Always consult a healthcare provider for personalized advice, especially before pursuing imaging or injections.