The sound of a shoulder popping, clicking, or cracking is medically termed crepitus. This noise occurs when the various structures of the complex shoulder joint—bones, tendons, ligaments, and cartilage—move against one another. While the sound can be alarming, the causes range widely, from entirely benign mechanical processes to signs of underlying structural issues. Understanding the difference between a harmless pop and one that indicates damage is important for knowing when to seek professional medical advice.
Harmless Causes of Shoulder Popping
The most frequent reason for a painless pop is a natural phenomenon known as cavitation, which also causes the sound when a person cracks their knuckles. This mechanical process involves the rapid formation and collapse of tiny gas bubbles within the synovial fluid, the viscous liquid that lubricates the joint. The sudden change in pressure creates a vacuum, and the subsequent burst of gas bubbles produces the audible pop. Since this mechanism does not involve any friction or damage to the joint tissues, it is considered a non-pathological occurrence that requires no treatment.
Another common source of painless shoulder clicking is benign tendon or ligament snapping, often referred to as Snapping Shoulder Syndrome. The shoulder joint is surrounded by numerous tendons, such as those of the biceps and rotator cuff, that must glide smoothly over bony prominences. A tendon can momentarily catch or snap over a piece of bone, like the head of the humerus, as the arm moves through a specific range of motion. This snapping sound is typically due to a normal variation in the person’s anatomy or minor imbalances in the surrounding musculature. If the pop is not accompanied by any discomfort, it is generally considered a safe, physiological noise.
Popping as a Sign of Joint Damage
When the popping sound is accompanied by pain, a grating sensation, or loss of function, it often signals an underlying structural problem within the joint.
Labral Tears
One frequent cause of painful clicking is a labral tear, which involves the ring of cartilage that lines the shoulder socket, called the labrum. A tear in this specialized tissue can create a flap that catches between the ball and socket as the arm moves, resulting in a deep, painful click or catching sensation. Injuries from acute trauma or repetitive overhead movements can lead to different types of tears, such as a SLAP tear, which affects the superior aspect of the labrum.
Osteoarthritis
Deterioration of the protective joint surfaces, such as in osteoarthritis, can also be a source of crepitus. Osteoarthritis involves the gradual wearing away of the smooth articular cartilage that covers the ends of the bones. When this cartilage erodes, the rougher bone surfaces begin to rub against each other during movement, which produces a coarse, grinding sound or sensation. This type of crepitus is often described as feeling like sand or gravel moving within the joint.
Shoulder Instability and Loose Bodies
Shoulder instability is another condition that can manifest with audible popping and clicking. Instability occurs when the ball of the shoulder joint moves excessively within the socket, often as a result of a past dislocation or ligament stretching. This excessive movement allows the head of the humerus to momentarily sublux (partially dislocate) or shift, causing a distinct pop as it returns to its normal position. The presence of loose bodies—small fragments of bone or cartilage floating within the joint capsule—can also cause intermittent catching and popping noises.
Rotator Cuff Pathology
Rotator cuff pathology, including severe tendonitis or a tear, can also lead to mechanical clicking. The rotator cuff muscles and tendons are responsible for stabilizing the shoulder and controlling its complex movements. When these tendons are inflamed or torn, the impaired movement mechanics can cause the humerus head to move improperly. This leads to impingement and subsequent clicking as the tendons rub against the bone above.
Accompanying Symptoms That Require Medical Attention
The presence of specific symptoms alongside shoulder popping should prompt a visit to a healthcare provider for a professional evaluation.
A persistent or increasing level of pain that occurs simultaneously with the pop is the most immediate indicator of a potential problem. If the pain interferes with daily activities or disrupts sleep, it suggests that the joint structure may be compromised.
Any noticeable change in the shoulder’s function, such as weakness or an inability to lift the arm, warrants medical attention. This functional loss can indicate a significant tear in a muscle or tendon that requires intervention. A noticeable limitation in the shoulder’s range of motion can also be a sign of underlying joint inflammation or mechanical blockage.
If the shoulder pop feels like the joint is suddenly “giving out” or if there is a sensation of instability, this may signal a problem with the ligaments or the joint capsule. An immediate onset of popping and pain following an acute injury, such as a fall, requires prompt medical assessment to rule out fractures or severe soft tissue tears. Finally, if the sound changes from a simple click to a grinding or grating sensation, a medical consultation is advisable.