Glossary

Deutsch: Schulterimpingement / Español: Pinzamiento de hombro / Português: Impacto no ombro / Français: Conflit sous-acromial / Italiano: Impingement della spalla

Shoulder impingement is a common condition in fitness and sports medicine that affects the functionality of the shoulder joint. This condition, often referred to as shoulder impingement, occurs when the tendons of the rotator cuff muscles become compressed or irritated as they pass through the subacromial space. It frequently arises in individuals who engage in repetitive overhead movements, such as weightlifters, swimmers, or athletes in throwing sports. While it may initially present as mild discomfort, untreated shoulder impingement can lead to chronic pain, reduced mobility, and long-term joint damage.

General Description

Shoulder impingement is a mechanical condition that primarily involves the compression of soft tissues within the shoulder joint. The shoulder is a ball-and-socket joint, offering a wide range of motion but also making it susceptible to instability and injury. The subacromial space, located beneath the acromion (a bony projection of the scapula), houses the rotator cuff tendons and the subacromial bursa. When this space narrows due to structural or functional abnormalities, the tendons and bursa can become pinched, leading to inflammation, pain, and impaired movement.

The rotator cuff consists of four muscles—supraspinatus, infraspinatus, teres minor, and subscapularis—that stabilize the shoulder and facilitate arm movements. The supraspinatus tendon, in particular, is most commonly affected in shoulder impingement due to its location directly beneath the acromion. Overuse, poor posture, or muscle imbalances can exacerbate the condition, as repetitive stress on the tendons leads to microtrauma and degenerative changes over time.

Shoulder impingement is often classified into two types: primary and secondary. Primary impingement is typically caused by anatomical factors, such as a hooked or curved acromion, which reduces the subacromial space. Secondary impingement, on the other hand, results from functional issues, including muscle weakness, joint instability, or poor movement patterns. Both types can coexist, particularly in individuals who engage in high-intensity training or sports that demand frequent overhead motions.

The condition is frequently associated with other shoulder pathologies, such as rotator cuff tendinitis, bursitis, or even partial-thickness tears. Early diagnosis and intervention are crucial to prevent progression, as chronic impingement can lead to irreversible damage to the rotator cuff tendons. Symptoms often include pain during overhead activities, weakness in the affected arm, and a limited range of motion, particularly when lifting the arm above shoulder height.

Causes and Risk Factors

Shoulder impingement can arise from a combination of intrinsic and extrinsic factors. Intrinsic causes are related to the individual's anatomy or physiological conditions, while extrinsic causes stem from external influences, such as training habits or environmental factors. Understanding these causes is essential for both prevention and treatment.

Anatomical variations, such as the shape of the acromion, play a significant role in primary impingement. Research has identified three types of acromion morphology: flat (Type I), curved (Type II), and hooked (Type III). Individuals with a Type III acromion are at a higher risk of developing impingement due to the reduced subacromial space (Bigliani et al., 1986). Additionally, bone spurs or calcific deposits on the underside of the acromion can further narrow the space, increasing the likelihood of tendon compression.

Extrinsic factors are often linked to repetitive stress and poor biomechanics. Athletes and fitness enthusiasts who perform overhead movements—such as swimming, tennis, baseball, or weightlifting—are particularly vulnerable. Poor technique, such as improper form during shoulder presses or pull-ups, can place excessive strain on the rotator cuff tendons. Similarly, muscle imbalances, where the larger muscles (e.g., deltoids or pectorals) overpower the smaller rotator cuff muscles, can lead to instability and impingement.

Age-related changes also contribute to the development of shoulder impingement. As individuals age, the tendons of the rotator cuff undergo degenerative changes, becoming less elastic and more prone to injury. Reduced blood flow to the tendons further impairs their ability to heal, increasing the risk of chronic inflammation. Additionally, sedentary lifestyles or prolonged desk work can lead to postural abnormalities, such as rounded shoulders or forward head posture, which alter the mechanics of the shoulder joint and predispose individuals to impingement.

Symptoms and Diagnosis

The symptoms of shoulder impingement typically develop gradually and may initially be dismissed as minor discomfort. However, as the condition progresses, the pain becomes more persistent and debilitating. The most common symptom is pain in the front or side of the shoulder, which worsens during overhead activities, such as lifting weights, throwing, or reaching. The pain may also radiate down the arm, particularly when the arm is raised above shoulder height or during movements that involve internal rotation, such as tucking in a shirt.

Individuals with shoulder impingement often experience stiffness and a reduced range of motion in the affected shoulder. Weakness in the arm may also be present, particularly when attempting to lift objects or perform resistance exercises. In some cases, a clicking or popping sensation may be felt during shoulder movements, which can indicate inflammation of the bursa or tendons. Night pain is another common complaint, as lying on the affected side can compress the inflamed tissues and exacerbate discomfort.

Diagnosis of shoulder impingement typically begins with a thorough physical examination by a healthcare professional. The examiner will assess the range of motion, strength, and pain response during specific movements. Special tests, such as the Neer test or Hawkins-Kennedy test, are commonly used to reproduce the symptoms of impingement. During the Neer test, the examiner stabilizes the scapula while passively raising the patient's arm, which compresses the rotator cuff tendons against the acromion. A positive result is indicated by pain during this movement (Neer, 1983).

Imaging studies, such as X-rays, ultrasound, or magnetic resonance imaging (MRI), may be used to confirm the diagnosis and rule out other conditions, such as rotator cuff tears or arthritis. X-rays can reveal anatomical abnormalities, such as bone spurs or acromion morphology, while ultrasound and MRI provide detailed images of the soft tissues, including the rotator cuff tendons and bursa. In some cases, a diagnostic injection of a local anesthetic into the subacromial space may be performed to determine whether the pain is originating from the impinged structures.

Application Area

• Sports and Athletics: Shoulder impingement is prevalent among athletes who engage in overhead sports, such as baseball, volleyball, swimming, and tennis. These activities involve repetitive arm movements that place stress on the rotator cuff tendons, increasing the risk of impingement. Coaches and trainers must emphasize proper technique, gradual progression in training intensity, and rotator cuff strengthening exercises to prevent injury.
• Weightlifting and Strength Training: Individuals who perform resistance training, particularly exercises that involve overhead pressing or pulling movements, are at risk of developing shoulder impingement. Poor form, excessive weight, or inadequate warm-up can exacerbate the condition. Fitness professionals should educate clients on proper shoulder mechanics and incorporate mobility and stability exercises into their training programs.
• Occupational Health: Workers in professions that require repetitive overhead movements, such as construction, painting, or assembly line work, are susceptible to shoulder impingement. Ergonomic interventions, such as adjusting workstations or incorporating rest breaks, can help reduce the risk of injury. Employers should provide training on proper lifting techniques and encourage employees to report early symptoms of shoulder discomfort.
• Rehabilitation and Physical Therapy: Shoulder impingement is a common condition treated in physical therapy clinics. Rehabilitation programs focus on reducing pain and inflammation, restoring range of motion, and strengthening the rotator cuff and scapular stabilizer muscles. Modalities such as ultrasound, ice therapy, and manual techniques may be used to alleviate symptoms and promote healing.

Well Known Examples

• Swimmer's Shoulder: Swimmer's shoulder is a term used to describe shoulder impingement in competitive swimmers. The repetitive overhead motion of freestyle, butterfly, and backstroke strokes places significant stress on the rotator cuff tendons, leading to inflammation and impingement. Swimmers often experience pain during the pull phase of the stroke, which can impair performance and require extended recovery periods.
• Baseball Pitcher's Shoulder: Baseball pitchers are highly susceptible to shoulder impingement due to the extreme range of motion and forces generated during the pitching motion. The late cocking and acceleration phases of pitching place immense stress on the rotator cuff and labrum, increasing the risk of impingement and other shoulder injuries. Pitchers with impingement may experience pain during the throwing motion, reduced velocity, and decreased accuracy.
• CrossFit Athletes: CrossFit training involves a variety of high-intensity exercises, including overhead presses, pull-ups, and snatches, which can predispose athletes to shoulder impingement. Poor technique, inadequate mobility, or rapid increases in training volume can exacerbate the condition. CrossFit coaches often incorporate shoulder mobility drills and rotator cuff strengthening exercises into their programming to mitigate the risk of injury.
• Manual Laborers: Workers in construction, painting, or manufacturing who perform repetitive overhead tasks are at risk of developing shoulder impingement. For example, electricians who frequently work with their arms raised above shoulder height may experience pain and inflammation in the shoulder joint. Ergonomic tools, such as extended handles or adjustable work platforms, can help reduce the strain on the shoulder.

Risks and Challenges

• Chronic Pain and Disability: If left untreated, shoulder impingement can progress to chronic pain and disability, significantly impacting an individual's quality of life. Persistent inflammation can lead to degenerative changes in the rotator cuff tendons, increasing the risk of partial or full-thickness tears. Chronic pain may also result in compensatory movement patterns, which can place additional stress on other joints, such as the elbow or spine.
• Rotator Cuff Tears: Shoulder impingement is a leading cause of rotator cuff tears, particularly in older adults. The repeated compression and irritation of the tendons can weaken their structure, making them more susceptible to tearing. Rotator cuff tears often require surgical intervention and extensive rehabilitation, which can result in prolonged recovery times and potential loss of function.
• Adhesive Capsulitis (Frozen Shoulder): Chronic shoulder impingement can lead to adhesive capsulitis, a condition characterized by stiffness, pain, and a significant loss of range of motion in the shoulder joint. The inflammation and reduced use of the shoulder can cause the joint capsule to thicken and contract, further restricting movement. Adhesive capsulitis often requires a lengthy rehabilitation process to restore function.
• Recurrence of Symptoms: Even after successful treatment, individuals with shoulder impingement are at risk of recurrence, particularly if they return to activities that place stress on the shoulder without addressing the underlying causes. Poor biomechanics, muscle imbalances, or inadequate rehabilitation can contribute to the re-emergence of symptoms. Ongoing maintenance exercises and proper technique are essential to prevent recurrence.
• Surgical Complications: In cases where conservative treatment fails, surgical intervention may be necessary to decompress the subacromial space. Procedures such as subacromial decompression or acromioplasty carry risks, including infection, nerve damage, or persistent pain. Additionally, surgery does not guarantee a full recovery, and some individuals may continue to experience limitations in shoulder function.

Similar Terms

• Rotator Cuff Tendinitis: Rotator cuff tendinitis refers to the inflammation of the tendons of the rotator cuff muscles, often resulting from overuse or repetitive stress. It is closely related to shoulder impingement, as the inflammation can contribute to the narrowing of the subacromial space and exacerbate impingement symptoms. Both conditions share similar causes and treatment approaches, including rest, physical therapy, and anti-inflammatory medications.
• Subacromial Bursitis: Subacromial bursitis is the inflammation of the subacromial bursa, a fluid-filled sac that cushions the rotator cuff tendons and the acromion. Bursitis often coexists with shoulder impingement, as the compression of the bursa can lead to inflammation and pain. Symptoms of bursitis include localized swelling, tenderness, and pain during overhead movements, which overlap with those of impingement.
• Labral Tear: A labral tear involves damage to the labrum, a ring of cartilage that surrounds the shoulder socket and stabilizes the joint. While labral tears are often associated with traumatic injuries, such as dislocations, they can also result from chronic impingement and repetitive stress. Symptoms of a labral tear may include deep shoulder pain, clicking or popping sensations, and instability, which can mimic or coexist with impingement.
• Shoulder Instability: Shoulder instability refers to the excessive movement of the humeral head within the shoulder socket, which can result from ligamentous laxity, muscle weakness, or traumatic injury. Instability can contribute to secondary impingement, as the abnormal movement of the joint increases the risk of tendon compression. Individuals with shoulder instability often experience pain, weakness, and a sensation of the shoulder "slipping out of place."

Summary

Shoulder impingement is a prevalent condition in fitness and sports medicine, characterized by the compression of the rotator cuff tendons and subacromial bursa within the shoulder joint. It commonly affects individuals who engage in repetitive overhead movements, such as athletes, weightlifters, and manual laborers. The condition can result from anatomical factors, such as a hooked acromion, or functional issues, including muscle imbalances and poor biomechanics. Symptoms typically include pain during overhead activities, reduced range of motion, and weakness in the affected arm.

Early diagnosis and intervention are crucial to prevent the progression of shoulder impingement and avoid complications such as rotator cuff tears or adhesive capsulitis. Treatment often involves a combination of rest, physical therapy, and anti-inflammatory measures, with surgical intervention reserved for severe cases. Prevention strategies, such as proper technique, gradual training progression, and rotator cuff strengthening exercises, are essential to reduce the risk of injury and recurrence. Understanding the causes, symptoms, and management of shoulder impingement can help individuals maintain shoulder health and continue participating in their chosen activities.

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References:

• Bigliani, L. U., Morrison, D. S., & April, E. W. (1986). The morphology of the acromion and its relationship to rotator cuff tears. Orthopedic Clinics of North America, 17(3), 419-428.
• Neer, C. S. (1983). Impingement lesions. Clinical Orthopaedics and Related Research, 173, 70-77.