The constant clicking, popping, or grinding sensation, known medically as crepitus, that comes from the shoulder joint is a common phenomenon. While this noise often causes immediate concern, it can result from simple, harmless events or indicate mechanical damage to the shoulder’s structures. Understanding the source of the noise helps differentiate between a benign occurrence and a symptom requiring professional attention.
Why Popping Can Be Normal
The most frequent and least concerning source of a popping sound is joint cavitation. This occurs when the pressure within the synovial fluid, the natural lubricant that fills the joint capsule, rapidly changes. The quick drop in pressure causes dissolved gases, primarily nitrogen, to form bubbles that suddenly collapse, releasing a small pop or crack. This painless popping is not a sign of damage or future arthritis.
Another non-pathological cause involves the brief friction of soft tissues moving over bony contours. Tendons or ligaments may momentarily catch on a slight prominence during certain movements, creating a quiet, non-painful click. If the sound is not accompanied by discomfort or loss of function, this noise is generally considered a normal function of a highly mobile joint.
Soft Tissue Causes of Shoulder Noise
When shoulder noise is accompanied by pain, it often points to irritation or inflammation of the surrounding soft tissues. One common cause is tendinitis, the inflammation of a tendon, frequently affecting the rotator cuff tendons. As a swollen or frayed tendon moves through the subacromial space, it can catch or rub against the bone, causing an audible click or snap.
Bursitis is the inflammation of the bursa, a fluid-filled cushion that normally reduces friction between tissues. When the bursa becomes inflamed, its smooth gliding function is compromised, leading to a painful popping or grating sensation, particularly with arm elevation. A less common cause is Snapping Scapula Syndrome (scapulothoracic bursitis). This occurs when the muscles or bursa between the shoulder blade and the rib cage are inflamed or unbalanced, causing a grinding or thumping sound as the scapula moves.
Structural Problems Inside the Joint
Persistent, painful popping or a feeling of the shoulder catching often suggests mechanical damage to the joint’s internal structures. The labrum, a ring of cartilage that deepens the shoulder socket, is a frequent source of these symptoms. A labral tear, resulting from trauma or repetitive overhead motion, allows torn tissue to get caught between the ball and socket, leading to a noticeable clunk, click, or grinding sensation.
Another significant structural problem is joint instability, where the head of the humerus shifts excessively within the socket. This instability can manifest as a partial dislocation, or subluxation, causing a distinct, often painful clunk as the joint momentarily slips and then relocates. This contributes to the ongoing feeling of the shoulder “giving way.” The chronic wear and tear of osteoarthritis can also generate joint noise. As the smooth articular cartilage degrades, the resulting bone-on-bone friction creates a coarse, grinding sound that often accompanies stiffness and reduced range of motion.
When to See a Doctor
While many shoulder noises are harmless, certain accompanying symptoms signal the need for professional medical evaluation. A doctor should be consulted if the popping sound is consistently accompanied by pain, instability, or the sensation that the joint is locking or catching. Prompt medical attention is required for any sudden onset of popping following an injury, such as a fall, especially if paired with immediate weakness or an inability to lift the arm.
A physician will typically begin by taking a detailed medical history and performing a physical examination to assess the shoulder’s range of motion and stability. Based on these findings, diagnostic imaging may be ordered, such as X-rays to view the bones or a magnetic resonance imaging (MRI) scan to visualize the soft tissues, including the labrum and rotator cuff tendons. Seeking an evaluation is important if symptoms persist for more than a few weeks or if the pain limits daily activities.