Shoulder popping, or crepitus, describes audible sounds from the shoulder joint, ranging from clicks, pops, and snaps to grinding sensations. While a common experience, these sounds can sometimes indicate an underlying issue.
Understanding Shoulder Anatomy
The shoulder is a complex ball-and-socket joint formed by three main bones: the humerus (upper arm bone), the scapula (shoulder blade), and the clavicle (collarbone). The humerus head fits into the glenoid, a shallow socket on the scapula. Soft tissues stabilize this bony architecture.
A fibrous joint capsule encloses the joint, holding the bones together. Inside, synovial fluid lubricates the joint. Ligaments are strong, fibrous bands that connect bones. Tendons, such as those of the rotator cuff, connect muscles to bones.
Harmless Reasons for Popping
One common cause of benign shoulder popping is joint cavitation, involving the formation and collapse of gas bubbles within the synovial fluid. This fluid contains dissolved gases. When the joint capsule stretches, pressure changes cause these gases to form bubbles.
As the joint moves, these bubbles rapidly collapse, creating the audible sound. This phenomenon is similar to cracking knuckles and is generally painless.
Another reason for popping sounds is the normal movement of tendons or ligaments. These structures can briefly catch or snap over bony prominences as the shoulder moves. For example, a tendon might momentarily glide over a bone and then snap back into place. These sounds occur without pain or instability.
More Serious Causes of Shoulder Popping
When shoulder popping is accompanied by pain, weakness, or a feeling of instability, it may signal a more significant underlying issue. One such condition is shoulder instability, where the humerus head partially or fully slips out of the glenoid socket. This can happen if the ligaments supporting the joint are stretched or torn, or if the glenoid socket itself is too shallow. A subluxation, a partial dislocation, often results in a distinct pop as the bone shifts and then returns to its proper position.
Labral tears are another potential cause of symptomatic shoulder popping. The labrum is a ring of cartilage that deepens the glenoid socket. A tear in this cartilage can lead to clicking, catching, or popping sensations. The torn piece of cartilage can interfere with the smooth movement of the humerus within the socket, creating mechanical symptoms.
Osteoarthritis, a degenerative joint disease, can also cause grinding or popping sounds in the shoulder. This condition involves the wearing down of the articular cartilage that covers the ends of the bones. As this protective cartilage erodes, bone can rub directly against bone, producing a creaking or grinding sensation that may include popping. The sounds are often accompanied by stiffness and pain, particularly with movement.
Rotator cuff issues, including tendinopathy or tears, can sometimes contribute to shoulder popping or clicking. The rotator cuff is a group of four muscles and their tendons that stabilize the shoulder and enable a wide range of motion. When these tendons become inflamed or torn, the normal mechanics of the shoulder can be altered. This disruption in smooth movement can occasionally lead to clicking or popping sounds, although grinding or a dull ache is more commonly associated with these conditions.
When to Consult a Doctor
While many instances of shoulder popping are benign, certain accompanying symptoms warrant a medical evaluation. It is advisable to consult a doctor if the popping is consistently associated with pain. Persistent pain suggests that the sound may be indicative of an underlying injury or condition rather than just harmless joint cavitation.
Seek medical attention if you experience weakness or difficulty moving your arm, especially when trying to lift it overhead or perform daily tasks. A feeling of instability, such as the shoulder “giving out” or feeling like it might dislocate, is another significant warning sign. Reduced range of motion, where you cannot move your arm as freely as before, also indicates a potential problem.
Other concerning symptoms include swelling, bruising, or a noticeable deformity around the shoulder joint. If the popping sound is new, significantly louder than before, or has changed in character, it is also prudent to get it checked by a healthcare professional. A medical expert can accurately diagnose the cause of the shoulder popping and recommend appropriate treatment to address any underlying issues.