Snapping Hip Syndrome, known clinically as Coxa Saltans, is a condition characterized by a palpable or audible clicking sensation that occurs during movement of the hip joint. This sensation is typically a “snap” or “pop” that occurs as a tendon or muscle moves across a bony structure in the hip. For many individuals, the condition is benign and painless, often presenting as only a minor annoyance. However, when the snapping leads to pain, inflammation, or limited mobility, it indicates a mechanical issue that warrants investigation to determine the precise underlying cause. Understanding the specific mechanism behind the sound is the first step toward effective management and treatment.
Classification of Snapping Hip Syndrome
The causes of the snapping sensation are categorized based on the anatomical location where the movement originates. This classification system provides a framework for diagnosis, dividing the syndrome into three distinct types: External, Internal, and Intra-Articular. The External type occurs on the side of the hip and is the most common presentation. The Internal type is felt deeper, anteriorly toward the groin area, involving structures close to the front of the hip joint. The Intra-Articular type is the least common and involves mechanical issues originating from within the hip joint’s socket and ball structure.
The External Mechanism
The External mechanism is the most frequently encountered cause of Snapping Hip Syndrome, involving soft tissues on the lateral (outer) side of the thigh. The snapping occurs as the Iliotibial (IT) Band passes back and forth across the greater trochanter of the femur, the large, bony bump felt on the side of the hip. If the band becomes tight or thickened, it can catch momentarily on the posterior aspect of the trochanter before abruptly snapping forward over the bone as the hip extends. This abrupt movement generates the audible or palpable snap. The tendon of the Gluteus Maximus muscle can also contribute to this external snapping mechanism.
This condition is frequently associated with activities that involve repetitive hip motion, such as running, cycling, and dancing. The friction created by the repetitive snapping can sometimes irritate the underlying trochanteric bursa, leading to painful inflammation known as trochanteric bursitis.
The Internal Mechanism
The Internal mechanism involves structures located deep in the anterior hip or groin region. This type is typically caused by the Iliopsoas tendon—a powerful hip flexor muscle group—catching or flicking over bony prominences as the hip moves. The bony structures commonly involved are the anterior aspect of the femoral head, the lesser trochanter, or the iliopectineal eminence on the pelvis. If the Iliopsoas tendon is excessively tight or enlarged, it can momentarily compress against these bony ridges. As the hip moves from a flexed position to an extended position, the tendon is forced to shift its course across the bone.
This rapid transition creates the deep, anterior popping sensation. Internal snapping is often provoked by specific movements, such as bringing the leg from an externally rotated and abducted position into a straight position. Inflammation of the iliopectineal bursa can also occur due to the repeated friction, leading to pain felt deep in the groin.
The Intra-Articular Mechanism
The Intra-Articular mechanism represents a distinctly different and potentially more serious category of Snapping Hip Syndrome because the cause originates from within the ball-and-socket joint itself. Unlike the External and Internal types, the intra-articular snap is a mechanical derangement within the joint space. This type is usually associated with pain and a feeling of instability or locking in the hip. A frequent cause is a Labral tear, which is damage to the ring of cartilage that lines the hip socket. A tear in this structure can cause a flap of cartilage to catch or click during movement.
Another cause involves loose bodies, which are small fragments of bone or cartilage that float freely within the joint. These fragments can become momentarily trapped between the joint surfaces, causing a sudden snap, catch, or lock.