Hip popping or clicking (crepitus or snapping) is a common sensation. This sound or feeling can originate from several structures both within and surrounding the complex ball-and-socket joint. The distinct sound is caused by soft tissues moving over bony parts, a change in joint fluid pressure, or damage to the cartilage inside the joint.
Mechanical Causes Outside the Joint (Snapping Hip Syndrome)
The most frequent cause of hip popping involves the movement of muscles and tendons sliding over bony prominences, a condition known as snapping hip syndrome, or coxa saltans. This snapping is typically categorized into two types based on its location outside the joint capsule (extra-articular).
External snapping occurs on the side of the hip when the iliotibial (IT) band or the tendon of the gluteus maximus muscle snaps across the greater trochanter. The greater trochanter is the large, bony knob on the outer thigh bone. When the hip moves, the taut band stretches and then rapidly recoils over the bone, creating the audible pop. While often painless, the repetitive friction can lead to inflammation of the underlying fluid-filled sac, known as bursitis.
Internal snapping is felt deeper in the front of the hip, near the groin. This type is caused by the iliopsoas tendon, a hip flexor, catching on a bony ridge at the front of the pelvis called the iliopectineal eminence. The tendon temporarily stretches and then quickly slips back into place as the leg moves from a flexed position to an extended one.
Benign Popping from Joint Fluid Changes
Another source of hip popping involves the fluid within the hip joint itself. This phenomenon, known as joint cavitation, occurs when the joint is stretched or moved rapidly, similar to what happens when cracking knuckles.
The hip joint is lubricated by synovial fluid, which contains dissolved gases such as nitrogen and carbon dioxide. When the joint surfaces are quickly separated, the pressure within the joint drops suddenly. This drop in pressure causes the dissolved gases to rapidly form a bubble or cavity, which then collapses, producing the characteristic popping sound. This sound is completely harmless and does not indicate any damage or wear to the joint. The sensation is painless and is simply a byproduct of the pressure change within the joint capsule.
Internal Joint Damage Requiring Intervention
Popping that originates from inside the hip joint (intra-articular) is a more serious concern, as it suggests mechanical damage to the joint’s internal structures. The pop in these cases is frequently described as a deep click, catch, or locking sensation.
One common cause is a tear in the labrum, which is a ring of fibrocartilage that lines the rim of the hip socket and helps maintain joint stability. A labral tear can result from trauma, repetitive motions, or underlying hip abnormalities. The torn piece of cartilage can catch in the joint during movement, and this type of internal popping is generally accompanied by sharp or dull pain deep in the groin.
Internal popping can also be caused by loose bodies, which are small fragments of bone or cartilage floating within the joint space. These fragments break off due to injury or advanced wear and tear from osteoarthritis. When a loose body gets caught between the ball and socket, it can cause a sudden, painful catching or locking sensation that results in an audible click. Osteoarthritis, where the protective cartilage wears away, can also create a grinding or popping noise due to irregular joint surfaces rubbing together.
Warning Signs and When to Consult a Doctor
A popping hip that is occasional and consistently painless is usually a benign mechanical issue or a result of joint fluid changes that do not require medical intervention. However, the presence of specific symptoms indicates that the popping warrants a professional evaluation.
You should consult a doctor if the popping is consistently accompanied by pain, particularly a sharp or stabbing sensation in the groin or deep in the hip. Other warning signs include a feeling of instability or weakness in the leg, or a noticeable decrease in the hip’s range of motion. If the joint feels like it is truly “locking up” or “catching,” or if the snapping is causing inflammation or swelling, medical assessment is necessary. You should also seek help if the symptoms interfere with normal daily activities like walking or sleeping.