© 2002 by the American Institute of Ultrasound in Medicine
J Ultrasound Med 21:753-758 • 0278-4297
Dynamic Sonography of External Snapping Hip Syndrome
Yun Sun Choi, MD,
Sung Moon Lee, MD,
Baek Yong Song, MD,
Sang Hyun Paik, MD and
Yong Kyu Yoon, MD
Departments of Diagnostic Radiology (Y.S.C., S.H.P., Y.K.Y.) and Orthopedic Surgery (B.Y.S.), Eulji Hospital, Eulji University School of Medicine, Seoul, South Korea; and Department of Diagnostic Radiology, Dongsan Medical Center, School of Medicine, Keimyung University, Daegu, South Korea (S.M.L.).
Address correspondence and reprint requests to Yun Sun Choi, MD, Department of Diagnostic Radiology, Eulji Hospital, 280-1 Hagye 1 Dong, Nowon-gu, Seoul 139-711, South Korea.
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Abstract
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Objective. To evaluate the dynamic sonographic findings of external snapping hip syndrome. Methods. Five patients with 7 cases of painful external snapping hip (3 male and 2 female; age range, 14–32 years; mean, 19 years) were examined with sonography. Two patients had bilateral snapping. Dynamic sonographic examinations of hips were performed with a linear 5- to 12-MHz transducer during hip motion. Results. Dynamic sonographic studies of the affected hip revealed causes of the external snapping hip in all cases. It was elicited by an abnormal jerky movement of the iliotibial band overlying the greater trochanter in 5 of 7 cases and of the gluteus maximus muscle in 2 cases. The iliotibial band over the greater trochanter was hypoechoic in 3 of the 5 cases and thickened in 1 case. Dynamic sonography showed good correlations between the jerky movements of the iliotibial band and the gluteus maximus muscle and the painful snapping reported by the patients. Conclusions. Dynamic sonography was helpful in the diagnosis of external snapping hip syndrome; it showed real-time images of sudden abnormal displacement of the iliotibial band or the gluteus maximus muscle overlying the greater trochanter as a painful snap during hip motion.
Key Words: dynamic sonography • external • gluteus maximus muscle • iliotibial band • snapping hip Abbreviations: MRI, magnetic resonance imaging
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Introduction
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Snapping hip syndrome has been described as hip pain accompanied by an audible snapping during motion of the hip or while walking. It is typically seen in young adults and is common in athletes and dancers.1,2 The variable causes of its external, internal, and intra-articular origins have been described.1–8 The most common external snapping hip has been associated with slipping of a thickened posterior border of the iliotibial band or anterior border of the gluteus maximus muscle over the greater trochanter (Fig. 1 ).2,3,5–8 Internal snapping hip is caused by snapping of the iliopsoas tendon over the iliopectineal eminence.1,6,7 Intra-articular snapping is due to an abnormality in the joint itself, such as intra-articular loose bodies, synovial osteochondromatosis, or a labrum tear.2
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Figure 1. Diagram showing a transverse section of the left hip. Note the relationships between the iliotibial band, the gluteus maximus muscle, and the surrounding structures.
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External snapping hip has been described many times in the orthopedic literature, but we know of only 1 radiologic imaging report.7 In the radiologic literature, internal snapping hip has largely concerned abnormal movement of the iliopsoas tendon.6,7 Recently, this entity came to the attention of radiologists, because sonographic examination allows noninvasive dynamic evaluation of the snapping iliotibial band or muscle during hip motion.7 The aim of this study was to evaluate the dynamic sonographic findings of external snapping hip syndrome and to review the literature.
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Materials and Methods
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We studied 5 patients (7 cases) with external snapping hip and pain over the greater trochanter during walking or hip motion (3 male and 2 female; age range, 14–32 years; mean, 19 years). Two patients reported bilateral snapping hips. No trauma history was evident in any case. One patient was a ballet dancer, and another was a policeman with a history of running, but with the exception of these 2 patients, none had a history of sports activity. The patients had no other medical problems. The mean duration of pain among these patients was 1 year (range, 6–18 months).
Sonographic examinations of hips were performed with a phased array linear 5- to 12-MHz transducer (HDI 3000; Philips Ultrasound, Bothell, WA) by 2 experienced musculoskeletal radiologists. In the static state, transverse and longitudinal sonographic scanning of the anterior and medial aspects of both hips and the lateral aspect of the greater trochanter was performed with patients in the supine position. In 3 of 7 cases, the hip was then examined in the decubitus state with the patients turned onto the contralateral side for dynamic sonography, and in 4 cases, the patients were examined while standing on the contralateral leg. With the transducer in the transverse plane over the greater trochanter, dynamic sonographic studies were performed during flexion and extension of the hip in the adducted state in 5 of 7 cases and with the hip in the adducted and internally rotated state and then in the flexed and externally rotated state in 2 of 7 cases (Fig. 2). Plain radiography was performed in all cases, and unenhanced magnetic resonance imaging (MRI) was performed on a 1.5-T system (Signa; GE Medical Systems, Milwaukee, WI) producing 5-mm contiguous T1-weighted spin echo (repetition time, 600 milliseconds; and echo time, 10 milliseconds) and T2-weighted fast spin echo (repetition time, 4000 milliseconds; and echo time, 96 milliseconds) axial and coronal images in 4 cases.
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Figure 2. Diagram showing the pathomechanics of a snapping iliotibial band and gluteus maximus muscle. A, When the hip is extended, the posterior border of the iliotibial band and the anterior border of the gluteus maximus muscle lie posterior to the greater trochanter. The transducer may be placed either transversely over the greater trochanter (open arrow A) or obliquely transverse over the greater trochanter, according to the hip movement (open arrow B). B, During flexion of the hip, the iliotibial band is tense and creates friction over the greater trochanter. As flexion increases, at some stage the iliotibial band is released, moving abruptly anteriorly with pain.
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Results
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Dynamic sonographic studies of the affected hips revealed the cause of the external snapping hip in all cases. In 5 of 7 cases, it was shown to be due to an abnormal jerky movement of the iliotibial band overlying the greater trochanter, and in 2 it was due to a jerky movement of the gluteus maximus muscle during hip motion. The hip movements that resulted in snapping of the iliotibial band are as follows: in 3 of 5 cases, snapping resulted when the adducted and extended hip was flexed (Fig. 3); and in the other 2 cases, snapping resulted when the adducted and internally rotated hip was flexed and externally rotated with the knee bent (Fig. 4). The iliotibial band was observed as a hyperechoic (n = 2), hypoechoic (n = 2), or thickened and hypoechoic (n = 1) structure superficial to the greater trochanter. No correlation was found between the duration of symptoms and the presence of signs of tendinopathy. Abnormal movement and contraction of the gluteus maximus muscles were seen during the flexion and extension of hips in 2 of the 7 cases (Fig. 5).
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Figure 4. Transverse sonograms at the level of the left greater trochanter from a 32-year-old man with a painful click in the left hip. A, When the hip is adducted and internally rotated and the knee is in flexion, the iliotibial band (arrows) is seen as a beaklike structure, with focal hypoechogenicity over the greater trochanter (GT). B, When the hip is flexed and externally rotated, the iliotibial band (arrows) slides abruptly over the anterior margin of the greater trochanter (GT). This movement coincides with a painful snap.
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Figure 5. Transverse sonograms at the level of the left greater trochanter from a 16-year-old girl with a painful click and palpable masses in both hips. A, When the hip is adducted and extended, the gluteus maximus muscle (GM) is located in the posterior side of the greater trochanter (GT) and is partly inserted in the iliotibial band (arrow). B, During flexion of the hip, the gluteus maximus muscle (GM) abruptly jerks anterior to the greater trochanter (GT). This movement correlates with a painful snap.
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Abrupt movements of the iliotibial band or the gluteus maximus muscle correlated with the painful click reported by the patients. The click could be observed by the examiner through the ultrasonic transducer at the posterior side of the greater trochanter and was confirmed by the patient when the iliotibial band or gluteus maximus muscle clicked. An abnormality of the iliopsoas tendon or the joint was not detected in all cases. Plain radiographs showed no abnormalities in all cases, and on MRI, intra-articular abnormalities were not shown in all 4 cases. Magnetic resonance imaging showed only the asymmetric thickness of both iliotibial bands in 1 patient with bilateral external snapping hips (Fig. 3A ).
Patients received medical treatment for 5 of 7 cases, and in 2 cases that had not responded to anti-inflammatory drug and rest treatment, the iliotibial band was elongated by the Z-plasty method. Pain was relieved by treatment in all patients, but in 5 cases with conservative treatment only, the patients still had snapping.
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Discussion
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Snapping hip syndrome is a well-recognized symptom complex that often comes to the attention of a clinician because the patient has pain with motion, and it can be classified as external, internal, or intra-articular according to the causes.1–8 An understanding of the precise cause increases the potential for successful treatment.
External snapping may occur when the thickened area at the posterior border of the iliotibial band or the anterior edge of the gluteus maximus muscle snaps forward over the greater trochanter with hip flexion.2,7–10 It may also be elicited by passive movement from an adducted and internal rotation of the hip into flexion and external rotation; at some stage during this movement, the hip clicks abruptly and with pain.10 In our studies, abrupt anterior movement of the iliotibial band or gluteus maximus muscle was observed when the extended hip was flexed in 5 cases and the adducted hip was flexed and externally rotated in 2 cases. In 4 of 7 cases, dynamic examinations were performed with the patients standing on the contralateral leg, because this more effectively reproduced the snap that would occur while standing or running. This suggests that weight bearing and contraction of the gluteus maximus muscle are important for generating the external snapping hip.
This entity may be painless in some patients.5–9 Friction of the iliotibial band or the gluteus maximus muscle over the greater trochanter may cause inflammation of the bursa. The pain may be due to trochanteric bursitis or tendonitis.8,10 In all of our cases, the patients had painful snapping. Three of 7 cases with accompanying pain had signs of iliotibial band tendinopathy. No case had signs of trochanteric bursitis. No normal thickness values are available for the tendons around the hip. However, on the basis of the idea that tendons are symmetric on both sides in given patients, tendinopathy is suggested when corresponding tendons are asymmetric or when tendons have abnormal echogenicity.7 Unfortunately, color or power Doppler sonography was not used in this study to detect inflammation. Moreover, the exact cause of pain was not found on sonography in 4 cases, and we did not have pathologic proof of a change in the iliotibial band or the gluteus maximus muscle in cases that had accompanying pain.
The treatment of external snapping hip syndrome includes conservative treatments such as rest, moist heat, stretching exercises, and anti-inflammatory drugs. Local anesthetics and steroids may also be injected into the trochanteric bursa. Surgical procedures can be performed in cases refractory to conservative treatment.7–10
External snapping hip syndrome may be familiar to orthopedic surgeons, because it is more easily diagnosed clinically than a snapping iliopsoas tendon.2,3,6–10 Once the external snapping hip has been shown in the appropriate clinical setting, no additional imaging study may be required before treatment. Recently, sonography has been used as a dynamic imaging modality, in which its real-time imaging capability enables the examiner to investigate the soft tissue as the patient moves a hip joint or contracts a muscle to show a pathologic characteristic.7 In this study, dynamic sonography allowed identification of the exact causes in all cases of external snapping hip syndrome. It is also possible that an examiner can sense the click through a transducer caused by the snapping movement of the iliotibial band or gluteus maximus during sonographic examination. Magnetic resonance imaging showed no abnormalities, as was expected, except in 1 case. External snapping hip syndrome is a kinematic disorder, which can be shown better during joint motion or muscle contraction, whereas MRI is a static technique. However, sonography has some limitations in terms of evaluating joint space. Magnetic resonance imaging or computed tomography and arthrography may be performed to exclude other causes such as a labrum tear, loose bodies in the hip joint, or bursitis. In this study, MRI was performed in 4 cases, and it did not exclude other potential causes in 3.
Our studies showed how dynamic sonographic examination can also noninvasively show the abnormal jerky movement of the iliotibial band or gluteus maximus muscle and can correlate this with the painful snap. We think that sonography should be performed when the diagnosis of external snapping hip syndrome is clinically uncertain or when it is associated with accompanying pain and shows no response to conservative treatment. In the future, additional sonographic studies may be required for full appreciation and evaluation of external snapping hip syndrome.
In conclusion, dynamic sonography is able to display real-time images of sudden abnormal jerky movement of the iliotibial band and the gluteus maximus muscle over the greater trochanter, which causes a painful snap during hip motion, and it can be used for an initial study to evaluate external snapping hip syndrome.
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Footnotes
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Received December 14, 2001, from the Departments of Diagnostic Radiology (Y.S.C., S.H.P., Y.K.Y.) and Orthopedic Surgery (B.Y.S.), Eulji Hospital, Eulji University School of Medicine, Seoul, South Korea; and Department of Diagnostic Radiology, Dongsan Medical Center, School of Medicine, Keimyung University, Daegu, South Korea (S.M.L.).
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References
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- Allen WC, Cope R. Coxa saltans: the snapping hip revisited. J Am Acad Orthop Surg 1995; 3:303–308.[Abstract]
- Jones FW. The anatomy of snapping hip. J Orthop Surg 1920; 2:1–3.
- Nunziata A, Blumenfeld I. Cadera a resorte: a proposito de una variedad. Prensa Med Argent 1951; 32:1997–2001.
- Binnie JF. Snapping hip (hanche a resort; schnellende hufte). Ann Surg 1913; 58:59–66.[Medline]
- Cardinal E, Buckwalter KA, Capello WN, Duval N. US of the snapping iliopsoas tendon. Radiology 1996; 198:521–522.[Abstract/Free Full Text]
- Pelsser V, Cardinal E, Hobden R, Aubin B, Lafortune M. Extraarticular snapping hip. AJR Am J Roentgenol 2001; 176:67–73.[Abstract/Free Full Text]
- Zoltan DJ, Clancy WG, Keene JS. A new operative approach to snapping hip and refractory trochanteric bursitis in athletes. Am J Sports Med 1986; 14:201–204.[Abstract/Free Full Text]
- Larsen E, Johansen J. Snapping hip. Acta Orthop Scand 1986; 57:168–170.[Medline]
- Faraj AA, Moulton A, Sirivastava VM. Snapping iliotibial band: report of ten cases and review the literature. Acta Orthop Belg 2001; 67:19–23.[Medline]
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Abstract
Introduction
