Shoulder Impingement: Causes, Exercises, and Treatment

Shoulder impingement

Shoulder impingement (or subacromial impingement syndrome) is one of the most common causes of shoulder pain, responsible for approximately 40-60% of all painful shoulders. It occurs when the tendons of the rotator cuff and the subacromial bursa are compressed (“impinged”) in the narrow space between the humeral head and the acromion — the bony process of the scapula that forms the “roof” of the shoulder.

The result is pain, especially during overhead arm movements, and a progressive deterioration of the tendons which, if left untreated, can lead to supraspinatus tendinitis, calcific tendinitis, and, in advanced cases, a rotator cuff tear.

The good news is that impingement responds very well to conservative treatment with physiotherapy and specific exercises, with success rates of 70-90% without the need for surgery.

Anatomy: The Subacromial Space

The shoulder is an extraordinarily mobile yet vulnerable joint. The subacromial space is the “corridor” located between:

• Superiorly: the acromion (bony process of the scapula) and the coracoacromial ligament
• Inferiorly: the humeral head

Through this space, which normally measures 10-15 mm, pass:

• The supraspinatus tendon (the most vulnerable rotator cuff tendon)
• The subacromial bursa (a cushion that reduces friction)
• The long head of the biceps tendon

When this space narrows — due to anatomical, postural, or functional reasons — the structures passing through it are compressed with each arm lift, generating the impingement.

Types of Impingement

External Impingement (most common)

Compression occurs between the acromion and the humeral head. Causes can be:

• Structural: a type III (hooked) acromion, which anatomically narrows the space
• Functional: alteration of the scapulohumeral rhythm, which causes the humeral head to “rise”

Internal Impingement

Less frequent, it occurs when the rotator cuff tendons are compressed between the humeral head and the glenoid (the articular cavity of the scapula) during abduction and external rotation movements. It is typical of overhead athletes (throwers, swimmers, volleyball players).

Causes and Risk Factors

Scapulohumeral Rhythm Alteration (Scapular Dyskinesis)

The most frequent and modifiable cause is scapular dyskinesis: an alteration in the movement of the scapula during arm elevation. Under normal conditions, the scapula rotates upward and outward to “make space” for the tendons under the acromion. If the scapula does not rotate correctly, the space narrows, and the tendons are compressed.

Causes of scapular dyskinesis include:

• Weakness of scapular stabilizing muscles (lower and middle trapezius, serratus anterior)
• Overactivity of the upper trapezius: the muscle “raises” the shoulder instead of rotating the scapula
• Tightness of the pectoralis minor: pulls the scapula forward (protraction) and limits its rotation
• Kyphotic posture: thoracic kyphosis shifts the scapula into protraction and reduces the subacromial space

Rotator Cuff Weakness

The rotator cuff has the fundamental task of “depressing” the humeral head during arm elevation, preventing it from rising against the acromion. When the cuff is weak, the humeral head migrates superiorly, and the subacromial space narrows.

Predisposing Factors

• Repetitive overhead activities: painters, construction workers, swimmers, volleyball players, tennis players
• Kyphotic posture: rounded shoulders and a curved back (thoracic pain) reduce the subacromial space
• Age: after 40-50 years, tendon degeneration and osteophyte formation narrow the space
• Acromial anatomy: a type III (hooked) acromion predisposes to impingement
• Overhead sports: swimming, volleyball, tennis, baseball, CrossFit

The kinetic chain plays a fundamental role: postural alterations of the pelvis and thoracic spine affect scapular mechanics and the shoulder.

Symptoms

Pain

• Location: anterolateral region of the shoulder, often radiating to the lateral arm down to the elbow
• Painful arc: pain typically occurs between 60° and 120° of arm abduction (the so-called “painful arc”). Below 60° and above 120°, the pain decreases
• Overhead movements: pain when lifting the arm overhead, putting on a jacket, combing hair, reaching for objects high up
• Night pain: pain when sleeping on the affected side — one of the most common complaints
• Insidious onset: the pain develops gradually, without a specific trauma

Clinical Tests

The physical therapist will evaluate the shoulder with specific tests:

• Neer’s Test: passive shoulder flexion with the scapula blocked — positive if it reproduces pain
• Hawkins-Kennedy Test: 90° flexion with forced internal rotation — the most sensitive test for impingement
• Jobe’s Test (empty can): assesses supraspinatus strength
• Painful arc: pain between 60° and 120° of active abduction

Diagnosis

Clinical Examination

Clinical examination is often sufficient for diagnosis. The tests described above, combined with the assessment of mobility, strength, and posture, allow for the identification of impingement and its causes.

Imaging Diagnostics

• Musculoskeletal ultrasound: visualizes the condition of the rotator cuff tendons, the subacromial bursa, and helps rule out tendon tears
• X-ray: highlights the shape of the acromion, acromial osteophytes, calcifications (calcific tendinitis)
• MRI: indicated if a rotator cuff tear is suspected or if symptoms do not improve with treatment

Treatment

Acute Phase (0-4 weeks)

• Relative rest: avoid overhead activities that trigger pain, but maintain shoulder movement
• Ice: 15-20 minutes after painful activities
• NSAIDs: as needed for pain and inflammation control
• DO NOT immobilize: complete rest is counterproductive as it weakens muscles and stiffens the shoulder

Physiotherapy

Physiotherapy is the first-line treatment and includes:

• Scapulohumeral rhythm re-education: the core of the treatment. Restore correct scapular movement to “open” the subacromial space
• Rotator cuff strengthening: specific exercises to strengthen the humeral head depressors
• Scapular stabilizer strengthening: lower and middle trapezius, serratus anterior
• Pectoralis minor and posterior capsule stretching: to restore correct scapular position
• Postural correction: treatment of thoracic kyphosis and shoulder protraction
• Manual therapy: mobilization of the glenohumeral joint and capsular structures

Exercises for Shoulder Impingement

The exercise program is the most effective long-term treatment. Your doctor or physical therapist will establish the progression based on individual response.

Phase 1 — Pain Control and Mobility

Pendulum exercise (Codman’s pendulum)

[IMAGE: Person slightly bent forward at the torso, one hand resting on a table for support. The painful arm hangs relaxed towards the floor and swings gently in small circles, back and forth and side to side, using gravity. Side view showing torso inclination and arm pendulum.]

Posterior capsule stretch (sleeper stretch)

[IMAGE: Person lying on the painful side with the affected arm forward at 90 degrees of shoulder flexion. The other hand gently pushes the wrist of the arm on the ground downwards, internally rotating the shoulder. Front view showing gentle forced internal rotation with assistance from the other hand.]

Phase 2 — Rotator Cuff Strengthening

External rotation with resistance band (side-lying)

[IMAGE: Person lying on the non-painful side. The arm on the painful side is resting with the elbow against the torso, flexed at 90 degrees. A rolled towel is between the elbow and the torso. The forearm rotates outwards (external rotation) against the resistance of a therapeutic band fixed in front. Front view showing the arc of rotation and the position of the resistance band.]

Standing external rotation at 0° with resistance band

[IMAGE: Person standing with the elbow of the painful arm close to the torso, flexed at 90 degrees. A therapeutic band is fixed to a stationary point laterally. The forearm rotates outwards against the resistance of the band, keeping the elbow at the torso. Front view showing the movement and the resistance of the band.]

Supraspinatus strengthening (full can)

[IMAGE: Person standing with the arm extended along the side, thumb pointing upwards (“full can” position — as if holding a can with the thumb up). The arm lifts laterally to about 45 degrees of abduction in the scapular plane (slightly forward), keeping the thumb up. Front view with detail of the angle and thumb position.]

Phase 3 — Scapular Stabilization

Prone scapular retraction (prone Y-T-W)

[IMAGE: Person lying prone on a mat or bench. The arms perform three positions: Y (arms extended overhead forming a Y), T (arms extended laterally forming a T), W (elbows flexed at the sides forming a W). In each position, the scapulae move closer to the spine and the arms lift slightly off the floor. Three positions shown from above.]

Push-up plus (serratus punch)

[IMAGE: Person in a push-up position (hands on the ground, arms extended). From the high push-up position, the scapulae protract (move away from the spine) by pushing the body further upwards, slightly rounding the upper back. This activates the serratus anterior. Side view with detail of scapular protraction.]

Wall slide

[IMAGE: Person standing with their back against the wall, feet 15 cm forward. Arms are bent with elbows at 90 degrees and the backs of the hands against the wall (candlestick position). Arms slide upwards along the wall maintaining contact of elbows and hands with the wall, then return to the starting position. Side view showing the ascent and contact with the wall.]

Phase 4 — Functional Return

Elevation with resistance band in the scapular plane

[IMAGE: Person standing with a resistance band under the foot of the painful side. The arm holds the band and lifts in the scapular plane (about 30-45 degrees in front of the frontal plane) up to 120-150 degrees of elevation, with the thumb pointing upwards. Side view with the scapular plane angle indicated.]

Recovery Times

When Is Surgery Necessary?

Surgery (arthroscopic acromioplasty) is indicated only after the failure of at least 3-6 months of adequate conservative treatment. It consists of removing the inferior portion of the acromion to increase the subacromial space. Results are generally good but not superior to physiotherapy in most cases.

Prevention

• Regular strengthening of the rotator cuff and scapular stabilizers: exercises 3 times a week
• Pectoral and posterior capsule stretching: after every overhead workout
• Correct posture: avoid kyphosis and shoulder protraction
• Correct sports technique: in swimming, volleyball, tennis — seek guidance from a qualified instructor
• Adequate warm-up: before overhead activities

For more information, consult the Complete Guide to Shoulder Pain.

Frequently Asked Questions (FAQ)

Frequently Asked Questions

What is shoulder impingement?

Shoulder impingement occurs when the rotator cuff tendons and subacromial bursa are compressed in the narrow space beneath the acromion. This compression typically results in pain, particularly during overhead arm movements.

What are the primary causes of shoulder impingement?

Key causes include altered shoulder blade movement, known as scapular dyskinesis, and imbalances or weakness in the rotator cuff muscles. These factors contribute to the narrowing of the subacromial space, leading to tendon compression.

How is shoulder impingement typically treated?

Treatment for shoulder impingement primarily involves physical therapy, focusing on specific exercises to improve rotator cuff strength and scapular stabilization. A physical therapist guides patients through phases of pain control, strengthening, and functional return. Early intervention is crucial to manage symptoms and prevent progression.

When might surgery be considered for shoulder impingement?

Surgery for shoulder impingement is generally considered when conservative treatments, such as physical therapy, do not provide sufficient relief after a dedicated period. It is typically reserved for cases where persistent symptoms significantly impact function and quality of life.

For a broader overview of related conditions, see our complete guide to shoulder pain.

Sources and Scientific References

1. Tauqeer S et al. (2024). Effects of manual therapy in addition to stretching and strengthening exercises to improve scapular range of motion, functional capacity and pain in patients with shoulder impingement syndrome: a randomized controlled trial. BMC Musculoskelet Disord. 25:192. DOI | PubMed
2. Ellenbecker TS et al. (2010). Rehabilitation of shoulder impingement syndrome and rotator cuff injuries: an evidence-based review. Br J Sports Med. 44:319-27. DOI | PubMed
3. Gebremariam L et al. (2014). Subacromial impingement syndrome–effectiveness of physiotherapy and manual therapy. Br J Sports Med. 48:1202-8. DOI | PubMed
4. Tahran Ö et al. (2020). Effects of Modified Posterior Shoulder Stretching Exercises on Shoulder Mobility, Pain, and Dysfunction in Patients With Subacromial Impingement Syndrome. Sports Health. 12:139-148. DOI | PubMed
5. Heron SR et al. (2017). Comparison of three types of exercise in the treatment of rotator cuff tendinopathy/shoulder impingement syndrome: A randomized controlled trial. Physiotherapy. 103:167-173. DOI | PubMed