Coxa Saltans: The Snapping Hip Revisited William C. Allen, MD, and Ray Cope, MD Abstract that it comes to lie anterior to the Coxa saltans, or “snapping hip,” has several causes. These can be divided into three greater trochanter. types: external, internal, and intra-articular. Snapping of the external type occurs The iliotibial tract has two major when a thickened area of the posterior iliotibial band or the leading anterior edge of musculotendinous attachments the gluteus maximus snaps forward over the greater trochanter with flexion of the proximally, the tensor fascia lata hip. The internal type has a similar mechanism except that it is the musculotendi- anteriorly and the gluteus maximus nous iliopsoas that snaps over structures deep to it (usually the femoral head and posteriorly. There is also an indirect the anterior capsule of the hip). Intra-articular snapping is due to lesions in the attachment to the gluteus medius joint itself. Diagnosis of the external and internal types is usually made clinically. through its overlying aponeurosis.7 Radiography can be useful in confirming the diagnosis, particularly when bursog- These muscles pull on the iliotibial raphy shows the iliopsoas tendon snapping with hip motion. Other radiologic tract, making it taut whether the hip modalities, such as computed tomography, magnetic resonance imaging, and is flexed or extended. The iliotibial arthrography, may also be helpful, especially when there is an intra-articular cause. tract is firmly attached on its deep Most cases of snapping hip are asymptomatic and can be treated conservatively. surface to the linea aspera and the However, if the snapping becomes symptomatic, surgery may be necessary. There posterior femur. Through this may also be a role for arthroscopy in the treatment of intra-articular lesions. broad-based attachment, the three J Am Acad Orthop Surg 1995;3:303-308 muscles gain an indirect insertion into the femur. Distally, the thick- ened posterior border of the iliotibial Coxa saltans, or “snapping hip,” is musculotendinous iliopsoas as it tract crosses the anterolateral aspect characterized by an audible snap- snaps over the structures located of the knee and inserts on the lateral ping, usually with flexion and behind it, the most common site tibia at Gerdy’s tubercle. The ante- extension of the hip during exercise being the femoral head.1,2 Intra-artic- rior portion of the tract flares out into or simply with normal activities of ular lesions may be due to a variety the lateral retinaculum, with some daily living. It is often accompanied of causes, such as synovial chondro- fibers attaching to the lateral patella. by pain. Most cases involve slip- matosis, loose bodies, fracture frag- Because the iliotibial tract ping of the gluteus maximus or the ments, and labral tears, which may remains taut throughout motion of iliotibial tract over the greater present a diagnostic problem for the the hip, not only does it act as a ten- trochanter. However, there are clinician. sion band on the lateral thigh, but other causes, and confusion can arise when symptoms are due to one External Type of these. The external type of snapping is Dr. Allen is Professor of Orthopaedic Surgery, commonly caused by the iliotibial School of Medicine, University of Missouri, tract sliding over the greater Columbia. Dr. Cope is Professor of Radiology and Orthopaedic Surgery, School of Medicine, Causes trochanter. A thickening of the pos- University of Missouri, Columbia. terior part of the iliotibial tract or the The causes of coxa saltans can be anterior border of the gluteus max- Reprint requests: Dr. Allen, University of Mis- classified as external, internal, and imus enhances the snapping.1,3-6 The souri Hospital, One Hospital Drive, M562, intra-articular. The external type of thickened band lies posterior to the Columbia, MO 65212. snapping involves the greater trochanter when the hip is in exten- trochanter and its overlying soft tis- sion and snaps forward over the Copyright 1995 by the American Academy of Orthopaedic Surgeons. sues. The internal type involves the greater trochanter with flexion, so Vol 3, No 5, September/October 1995 303 Coxa Saltans any small anatomic change or iliopectineal eminence and the ante- Other areas behind the iliopsoas swelling may precipitate snapping rior inferior iliac spine.4 The musculo- that are known to cause snapping over the greater trochanter. The tendinous junction consistently occurs are a prominence of the iliopectineal greater trochanteric bursa lies at the level of this osseous groove, ridge and exostoses of the lesser between the iliotibial tract and the with the bulk of the tendon being infer- trochanter. In some patients, a dis- greater trochanter, and it may ior to the bony pelvis. From its most crete tendinous slip arises from a become inflamed and cause pain lateral location, when the hip is in full position superior to the bony pelvis,4 when snapping occurs. flexion, abduction, and external rota- and this slip may snap on the tion, to its most medial position, when iliopectineal ridge. Internal Type the hip is in extension, adduction, and Another cause of internal snap- The internal type of coxa saltans internal rotation, the major conjoined ping is attributable to the iliopsoas was first reported from Argentina in iliopsoas tendon remains in this bursa. The bursa has well-defined a brief report of three cases.6 It was groove.1,4 However, it moves from the anatomic boundaries, with the mus- postulated that the psoas tendon lateral to the medial side of the culotendinous part of the iliopsoas was slipping over the iliopectineal femoral head when the hip moves muscle lying anterior and the cap- eminence. Following iliopsoas from flexion to extension, and it sule of the hip joint and the lengthening, good results were moves from the medial to the lateral iliopectineal eminence being poste- obtained in two of the three patients. side of the femoral head when the hip rior. The bursa extends medially to Studies reported from the Univer- moves from extension to flexion (Fig. the iliopectineal line and laterally to sity of Missouri pertaining to the inter- 1). In the majority of symptomatic the anterior inferior iliac spine. nal type of snapping have shown that cases of internal-type coxa saltans, it is Proximally, it may extend up into the iliacus and psoas muscles con- this motion back and forth over the the iliac fossa; distally, to the lesser verge and fuse together as they pass femoral head that causes the snap- trochanter. It is the largest synovial through a groove between the ping. bursa in the body and can measure up to 7 cm in length and 4 cm in width.8 The bursa and the hip joint communicate in approximately 15% of hips; this communication may be secondary to attritional changes.4 Intra-articular Type If the snapping is caused by an intra-articular lesion, such as a loose body, it may occur intermittently if the loose body can lodge in the foveal area of the acetabulum or in a redun- dant synovial fold. Most of the intra- articular causes of snapping have a distinctive presentation and should not be confused with snapping of the external or internal type. Tears of the acetabular labrum are included as a possible cause of snap- ping, but such tears far more often cause pain.9-11 They are usually located in the posterosuperior por- tion of the labrum, which seems to ABbe the most vulnerable to mechani- cal stress.9 There is also an increased incidence of labral tears in dysplastic Fig. 1 A, With flexion of the hip, the iliopsoas tendon shifts laterally in relation to the cen- ter of the femoral head. B, With extension of the hip, the iliopsoas tendon shifts medially in hips, which may be due to the con- relation to the center of the femoral head. stant increased pressure on the rim of the acetabulum.10 In severe 304 Journal of the American Academy of Orthopaedic Surgeons William C. Allen, MD, and Ray Cope, MD trauma cases, such as a dislocation When the external type of coxa for anterolateral knee instability, with a large tear of the labrum, saltans is suspected, the patient is with the mechanism being related to actual locking may occur. placed on his or her side with the alterations in the mechanics of the affected leg up. The hip is then iliotibial tract in susceptible individ- flexed actively by the patient as the uals.17 History and Physical examiner palpates the area of the Other unusual causes of snapping Examination greater trochanter so that the snap- include capsular and synovial folds, ping can be felt. As in the internal synovial chondromatosis, loose In cases of coxa saltans of the inter- type of coxa saltans, the diagnosis is intra-articular bodies, exostoses,12 nal and external types, the history is corroborated if the snapping can be and stenosing tenosynovitis of the usually fairly diagnostic in itself. blocked by applying pressure at the iliopsoas tendon and sheath near its The patient will describe a snapping, level of the greater trochanter. femoral insertion.18,19 In children painful sensation and will usually Both the internal and external and teenagers, habitual hip disloca- point to the area of the greater types of snapping can sometimes be tion may occasionally present as a trochanter or the front of the hip. In best reproduced by the patient when snapping hip.20,21 Slipping of the addition, the patient will frequently he or she is standing. This is particu- iliofemoral ligaments over the volunteer to demonstrate the snap- larly true of the external type. When femoral head19 and slipping of the ping.