Shoulder impingement occurs when the rotator cuff, a group of four muscles connecting your shoulder blade to your upper arm bone, gets pinched or rubbed by the top outer edge of the shoulder blade, known as the acromion. This often happens due to swelling that reduces the already small space for the rotator cuff. The condition, also called impingement syndrome, primarily causes pain, especially during movement, as the rotator cuff is essential for lifting your arm overhead and rotating it.

Types of Shoulder Impingement

• Rotator cuff tendinitis involves inflammation or irritation of the tendons supporting the rotator cuff, causing them to swell and lead to impingement.
• Shoulder bursitis is the inflammation of a bursa, a fluid-filled sac that cushions the space between the rotator cuff tendons and the acromion; its swelling can also cause impingement symptoms.
• Acromion deformity, where the acromion is naturally curved or hooked, or develops bone spurs with age, can directly rub against the rotator cuff.

Symptoms and Prevalence

Shoulder pain, typically felt at the front of the shoulder and sometimes radiating to the side of the arm, is the hallmark symptom. This pain often worsens at night or with movements like reaching overhead, lifting the arm, or reaching behind the back. The shoulder might also feel tender. Specifically, rotator cuff tendinitis can also cause stiffness, swelling, skin discoloration, and a cracking or popping sensation during movement.

Causes and Risk Factors

Most often, shoulder impingement is an overuse injury developing over time due to repetitive overhead rotational motions that stress the shoulder joint. Activities common in sports like swimming, baseball, volleyball, and tennis, or jobs such as construction, painting, and window washing, are frequent culprits. While usually gradual, trauma from a fall or accident can also cause it suddenly. Some cases develop without a clear reason (idiopathically).

Diagnosis and Management

A healthcare provider typically diagnoses shoulder impingement through a physical examination, assessing your shoulder’s range of motion and discussing your symptoms and activities. Imaging tests like X-rays, MRI, or ultrasound may be used to visualize the joint, identify specific causes like acromion shape, and rule out other conditions such as rotator cuff tears or arthritis.

Initial treatment focuses on rest from aggravating activities, physical therapy to strengthen the shoulder and improve mobility, and icing. Over-the-counter NSAIDs can help manage pain and swelling, while corticosteroid injections may be used for more significant inflammation. If these conservative measures don’t provide relief, arthroscopic shoulder decompression surgery, which involves removing part of the acromion to create more space, might be recommended.