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The Snapping Iliopsoas Tendon: New Mechanisms Using Dynamic Sonography

¹ All sauthors: Département de Radiologie, Centre Hospitalier Universitaire de Montréal (CHUM)–Hôpital Saint-Luc, 1058, rue Saint-Denis, Montréal, QC H2X 3J4, Canada.

Received April 10, 2007; accepted after revision September 11, 2007.

 
Address correspondence to É. Cardinal (etienne.cardinal{at}videotron.ca).

Abstract

Top Abstract Introduction Materials and Methods Results Discussion References

 
OBJECTIVE. The purpose of our study was to describe new mechanisms responsible for the snapping iliopsoas tendon using dynamic sonography.

MATERIALS AND METHODS. We reviewed the video recordings obtained during dynamic sonography studies used to establish the diagnosis of 18 snapping iliopsoas tendons in 14 patients (nine females and five males; age range, 13–50 years) who presented clinically with either unilateral (n = 10) or bilateral (n = 4) snapping hips. During dynamic imaging, the transducer was positioned in a transverse oblique plane just above the hip joint parallel to the pubic bone. For all patients, the hip movement that generated the snapping consisted of bringing the hip from flexion–abduction–external rotation back to the neutral position.

RESULTS. In 14 of 18 hips, the snapping was provoked by the sudden flipping of the iliopsoas tendon around the iliac muscle, allowing abrupt contact of the tendon against the pubic bone and producing an audible snap. Other causes of snapping iliopsoas tendon were bifid tendon heads flipping over one another (n = 3) and iliopsoas tendon impinging over an anterior paralabral cyst (n = 1).

CONCLUSION. New mechanisms of snapping iliopsoas tendon have been described using dynamic sonography. Sudden iliopsoas tendon flipping over the iliac muscle was the most common cause of snapping hip.

Keywords: iliopsoas tendon • musculoskeletal imaging • snapping hip • sonography • sports medicine

Introduction

Top Abstract Introduction Materials and Methods Results Discussion References

 
Snapping hip syndrome was first described by Nunziata and Blumenfeld in 1951 and is characterized by a sudden, painful, and audible snapping of the hip [1]. Painful symptoms are reproduced during specific movements of the hip but most frequently when the hip moves from a position of flexion–abduction–external rotation (frogleg position) to the neutral position [2]. Snapping hips are typically seen in young athletic individuals such as ballet dancers [3].

The causes of snapping hip may be intraarticular (e.g., labral tear, chondral defect, loose bodies) or extraarticular. Extraarticular causes of snapping hip may involve the iliopsoas tendon or the iliofemoral ligament anteriorly and the iliotibial band or gluteus maximus laterally [4–9]. The ilio psoas tendon has been suggested as the most common cause of snapping hip [2]. Arthrography, iliopsoas bursography, and more recently sonography have been used to show the sudden abrupt movement of the iliopsoas tendon during snapping when the patient was performing hip extension from a position of flexion–abduction–external rotation [5, 6, 10, 11]. The proposed mechanism to explain the snapping was a conflict between the iliopsoas tendon and the iliopectineal eminence or the lesser trochanter [3, 5]. The conflict between the tendon or ligament and the bone structures was, however, never documented by direct observation in these studies and remained hypothetical.

With its real-time imaging capabilities, sonography is well suited for dynamic evaluation of muscles and tendons around the hip during motion and has been used to show the correlation between abnormal iliopsoas tendon motion and the painful snap [2, 11–13]. The exact mechanism by which this abnormal iliopsoas tendon motion is generated has not been shown, however. The purpose of our study was to report new mechanisms responsible for iliopsoas tendon snapping.

Materials and Methods

Top Abstract Introduction Materials and Methods Results Discussion References

 
A retrospective review of sonography studies and video recordings obtained during standardized dynamic examinations of 14 consecutive patients (nine females and five males; age range, 13–50 years) who presented clinically with painful unilateral (n = 10) or bilateral (n = 4) snapping iliopsoas tendon and eight normal hips from the asymptomatic side was performed. All patients had a diagnosis of snapping iliopsoas tendon confirmed with dynamic sonography made at the time of the study. The review was made in consensus by a radiology fellow and a musculoskeletal radiologist with 14 years' experience in musculoskeletal sonography. All studies were performed by experienced musculoskeletal sonographers. Video recordings for two asymptomatic hips were not available for review. All sonography studies were performed using a 5-12–MHz linear array transducer (ATL HDI 5000, Philips Medical Systems). All sonography examinations included an initial static study, with the patient's leg in a resting position and the patient lying supine, and a dynamic study.

The static part of the sonography study was performed with transverse and longitudinal images of the iliopsoas tendons [14]. The iliopsoas tendon was assessed for signs of tendinosis (i.e., hypoechogenicity, loss of fibrillary pattern), tears (i.e., well-defined hypoechoic or anechoic intratendinous image), and associated iliopsoas bursitis (i.e., synovial thickening or fluid in the bursa). The dynamic part of the sonography study was performed with the transducer positioned in a transverse oblique plane just above the hip joint parallel to the pubic bone. Patients were then asked to mobilize the hip to reproduce the snap by bringing the hip into flexion–abduction–external rotation (frogleg position) and then back into full extension (neutral position) [15]. The same dynamic study was also performed for the normal asymptomatic hips. The videos were reviewed for the iliopsoas tendon motion and the relationship of that tendon with its muscle and with bone landmarks.

Results

Top Abstract Introduction Materials and Methods Results Discussion References

 
When the hip is in the neutral position, the iliopsoas tendon of both symptomatic and asymptomatic patients was seen overlying the superior pubic ramus, posterior to its muscle. Two patients showed a bifid tendon bilaterally. Five snapping hips had signs of iliopsoas tendinosis. Neither a tear nor bursitis was identified.

Dynamic sonography of normal asymptomatic hips (n = 8) as patients moved from the neutral position to the frogleg position showed lateral displacement of the iliopsoas muscle in combination with a rotating movement (counterclockwise on the right side and clockwise on the left side). During this flexion–abduction–external rotation of the hip, the ilio psoas tendon was also seen to move laterally and to rotate anteriorly to part of the iliopsoas muscle. When the hip is brought back to the neutral position, the iliopsoas tendon slides smoothly and rotates back until it returns posteromedially to the muscle onto the pubic bone.

In 14 of the 18 snapping hips, the same iliopsoas tendon snapping mechanism was identified (Figs. 1A, 1B, 1C, 1D and 2A, 2B, 2C). At rest, the iliopsoas tendon is in contact with the superior pubic ramus (Fig. 1A). With flexion–abduction–external rotation of the hip, the iliopsoas tendon rolls laterally and anteriorly over part of its muscle (Fig. 1B). In normal hips, a rotation movement that is clockwise for the left hip and counterclockwise for the right side accompanies this tendon motion. When the hip reaches the frogleg position, part of the iliopsoas muscle is located between the iliopsoas tendon and the pubic bone. As the hip is brought back to the neutral position and as the iliopsoas tendon follows a reverse path (medially and posteriorly), the muscle, at one point, is suddenly released laterally, thereby allowing an abrupt return of the iliopsoas tendon against the pubic bone, producing an audible snap (Fig. 1C). This abrupt iliopsoas tendon snap occurred about midway to neutral position. One of these patients also had an iliopsoas tendon snapping when the tendon rolled over the muscle during flexion–abduction–external at the level of the anteroinferior iliac spine. Throughout dynamic sonography, the iliopectineal eminence was always located medial to the psoas tendon and was not involved in the snapping mechanism.

View larger version (150K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1A —Left hip iliopsoas tendon snapping over iliac muscle in 29-year-old man. Video recording of this case (Fig. S1E) can be seen in the AJR electronic supplement to this article, available at www.ajronline.org, and presents more detail than the images printed here. At rest, hyperechoic oval-shaped iliopsoas tendon (arrow) is located anterior to superior pubic ramus (SPR) and posterior to hypoechoic iliac muscle (m and arrowhead).

View larger version (142K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1B —Left hip iliopsoas tendon snapping over iliac muscle in 29-year-old man. Video recording of this case (Fig. S1E) can be seen in the AJR electronic supplement to this article, available at www.ajronline.org, and presents more detail than the images printed here. With flexion–abduction–external rotation of hip, iliopsoas tendon (arrow) rolls laterally and anteriorly over muscle (arrowhead), trapping it between tendon and superior pubic ramus (SPR).

View larger version (146K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1C —Left hip iliopsoas tendon snapping over iliac muscle in 29-year-old man. Video recording of this case (Fig. S1E) can be seen in the AJR electronic supplement to this article, available at www.ajronline.org, and presents more detail than the images printed here. As hip is progressively brought back to neutral position, iliopsoas tendon (arrow) and trapped component of muscle (arrowhead) follow progressively reverse path (medially and posteriorly for tendon and laterally for muscle).

View larger version (148K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1D —Left hip iliopsoas tendon snapping over iliac muscle in 29-year-old man. Video recording of this case (Fig. S1E) can be seen in the AJR electronic supplement to this article, available at www.ajronline.org, and presents more detail than the images printed here. At one point, muscle (arrowhead) is suddenly released laterally, allowing abrupt return of iliopsoas tendon (arrow) against superior pubic ramus (SPR), producing audible snap.

View larger version (8K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2A —Diagrams illustrate snapping iliopsoas tendon from transverse oblique view above level of hip joint. As hip is flexed, abducted, and externally rotated, iliopsoas tendon (T) rolls laterally over part of iliac muscle (m) that becomes interposed between tendon and superior pubic ramus (SPR).

View larger version (8K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2B —Diagrams illustrate snapping iliopsoas tendon from transverse oblique view above level of hip joint. As hip is brought back to neutral position, tendon (T) follows reverse path (medially and posteriorly) and part of its muscle (m) is trapped between its tendon and superior pubic ramus.

View larger version (7K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2C —Diagrams illustrate snapping iliopsoas tendon from transverse oblique view above level of hip joint. At one point, muscle (m) is suddenly released laterally, allowing abrupt return of tendon (T) against pubic bone, producing audible snap.

View larger version (75K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3A —Right hip bifid iliopsoas tendon with medial and lateral heads snapping over one another in 13-year-old girl. Video recording of this case (Fig. S3E) can be seen in the AJR electronic supplement to this article, available at www.ajronline.org, and presents more detail than the images printed here. At rest, two heads of bifid iliopsoas tendon are located anterior to superior pubic ramus (SPR) and posterior to muscle (m). Hyperechoic medial head of one iliopsoas tendon (arrow) neighbors lateral head of second iliopsoas tendon (arrowhead), which shows less hyperechoic pattern than medial head due to anisotropy.

View larger version (68K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3B —Right hip bifid iliopsoas tendon with medial and lateral heads snapping over one another in 13-year-old girl. Video recording of this case (Fig. S3E) can be seen in the AJR electronic supplement to this article, available at www.ajronline.org, and presents more detail than the images printed here. With flexion–abduction–external rotation of hip, medial head (arrow) of bifid iliopsoas tendon is flipping laterally over lateral head (arrowhead), producing first audible snap. SPR = superior pubic ramus.

View larger version (72K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3C —Right hip bifid iliopsoas tendon with medial and lateral heads snapping over one another in 13-year-old girl. Video recording of this case (Fig. S3E) can be seen in the AJR electronic supplement to this article, available at www.ajronline.org, and presents more detail than the images printed here. As hip is progressively brought back to neutral position, medial head (arrow) of iliopsoas tendon (now located laterally) follows reverse path medially, overlying lateral head (arrowhead) that maintained more medial position. SPR = superior pubic ramus.

View larger version (69K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3D —Right hip bifid iliopsoas tendon with medial and lateral heads snapping over one another in 13-year-old girl. Video recording of this case (Fig. S3E) can be seen in the AJR electronic supplement to this article, available at www.ajronline.org, and presents more detail than the images printed here. At one point, close to neutral position of hip, true medial head (arrow) is suddenly released over lateral head (arrowhead) against superior pubic ramus (SPR), producing second audible snap.

View larger version (9K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4A —Diagrams illustrate bifid iliopsoas tendon snapping from transverse oblique view above level of right hip joint. m = iliac muscle, lh = lateral head of bifid iliopsoas tendon, mh = medial head of bifid iliopsoas tendon. In neutral position, medial head and lateral head of double iliopsoas tendons are overlying superior pubic ramus (SPR).

View larger version (8K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4B —Diagrams illustrate bifid iliopsoas tendon snapping from transverse oblique view above level of right hip joint. m = iliac muscle, lh = lateral head of bifid iliopsoas tendon, mh = medial head of bifid iliopsoas tendon. As hip is flexed, abducted, and externally rotated, medial head of double tendon moves anteriorly and laterally to stable lateral head with rotation motion.

View larger version (9K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4C —Diagrams illustrate bifid iliopsoas tendon snapping from transverse oblique view above level of right hip joint. m = iliac muscle, lh = lateral head of bifid iliopsoas tendon, mh = medial head of bifid iliopsoas tendon. Then medial head of double psoas tendon abruptly flips over lateral head during hip motion, provoking snapping.

View larger version (9K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4D —Diagrams illustrate bifid iliopsoas tendon snapping from transverse oblique view above level of right hip joint. m = iliac muscle, lh = lateral head of bifid iliopsoas tendon, mh = medial head of bifid iliopsoas tendon. As hip is brought back to neutral position, medial head of iliopsoas tendon (now located laterally) follows reverse path.

View larger version (9K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4E —Diagrams illustrate bifid iliopsoas tendon snapping from transverse oblique view above level of right hip joint. m = iliac muscle, lh = lateral head of bifid iliopsoas tendon, mh = medial head of bifid iliopsoas tendon. Medial head of iliopsoas tendon flips abruptly over its lateral head and produces second snapping against pubic bone.

View larger version (103K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5A —Right hip iliopsoas tendon snapping over paralabral cyst in 50-year-old woman ballet teacher. Video recording of this case (Fig. S5E) can be seen in the AJR electronic supplement to this article, available at www.ajronline.org, and presents more detail than the images printed here. At rest, hyperechoic iliopsoas tendon (arrow) is located anterior to superior pubic ramus (SPR) and medial to hypoechoic and heterogeneous paralabral cyst (arrowhead).

View larger version (101K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5B —Right hip iliopsoas tendon snapping over paralabral cyst in 50-year-old woman ballet teacher. Video recording of this case (Fig. S5E) can be seen in the AJR electronic supplement to this article, available at www.ajronline.org, and presents more detail than the images printed here. With full flexion–abduction–external rotation of hip, iliopsoas tendon (arrow) rolls laterally and anteriorly over cyst (arrowhead), snapping first time as it flips over cyst and contacts abruptly superior pubic ramus (SPR).

View larger version (106K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5C —Right hip iliopsoas tendon snapping over paralabral cyst in 50-year-old woman ballet teacher. Video recording of this case (Fig. S5E) can be seen in the AJR electronic supplement to this article, available at www.ajronline.org, and presents more detail than the images printed here. As hip is progressively brought back to neutral position, iliopsoas tendon (arrows) follows reverse path medially (C) until it flips again over cyst (D) and produces another snap on superior pubic ramus (SPR). Arrowheads point to cyst.

View larger version (106K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5D —Right hip iliopsoas tendon snapping over paralabral cyst in 50-year-old woman ballet teacher. Video recording of this case (Fig. S5E) can be seen in the AJR electronic supplement to this article, available at www.ajronline.org, and presents more detail than the images printed here. As hip is progressively brought back to neutral position, iliopsoas tendon (arrows) follows reverse path medially (C) until it flips again over cyst (D) and produces another snap on superior pubic ramus (SPR). Arrowheads point to cyst.

View larger version (45K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6A —Diagrams illustrate iliopsoas tendon snapping over paralabral cyst. As hip is moved from neutral position to frogleg position, tendon moves laterally and flips abruptly over paralabral cyst, snapping against pubic bone.

View larger version (49K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6B —Diagrams illustrate iliopsoas tendon snapping over paralabral cyst. As hip is brought back from frogleg position to neutral extended position, tendon moves medially, suddenly flipping over paralabral cyst for second time.

Top Abstract Introduction Materials and Methods Results Discussion References

At the inguinal level, where we evaluated the iliopsoas musculotendinous junction, the iliac muscle over which the snapping occurs is located more laterally than the psoas tendon and muscle [17, 18]. The iliac muscle will merge more distally with its tendon on the psoas tendon to make up the iliopsoas tendon [17, 18]. Therefore, the tendon identified to be involved in the snapping mechanism at the inguinal level does correspond to the psoas tendon of the iliopsoas muscle complex. However, the terms "iliopsoas tendon" and "psoas tendon" have been used interchangeably in the medical literature.

Our study of patients with snapping iliopsoas tendon provides new insights about the underlying mechanism by showing how the iliopsoas tendon is rolling over the medial part of the iliac muscle onto the superior pubic ramus to produce the snap. This mechanism was present in the majority of our patients (14 of 18 snapping hips). Interestingly, the iliopectineal eminence always remained medial to the iliopsoas tendon and was not involved in the tendon snapping in any of our patients. Moreover, since Lyons and Peterson [5] proposed the hypothesis that iliopsoas tendon snapping could involve the iliopectineal eminence, there has been no direct objective observation of this mechanism [2, 6, 10, 11, 13, 19]. Previous dynamic sonography studies on iliopsoas tendon snapping refer to this mechanism when identifying the abrupt iliopsoas tendon motion, but they have not shown evidence of the tendon impinging on the iliopectineal eminence [2, 11, 19, 20]. The findings in our study suggest that this dynamic interaction between the ilio psoas tendon and its muscle represents the most common cause of psoas tendon snapping rather than impingement with the iliopectineal eminence.

The snapping iliopsoas tendon seems to occur in a young, physically active population. This may be due to young athletic individuals being able to generate the wide range of hip movement that may be needed to cause the snapping hip, as may be seen in karate and ballet [3]. Snapping hip has a special importance for professional dancers and certain sports that demand repeated elevations of the leg over the horizontal line in abduction [19].

During our dynamic sonography evaluations, the medial part of the iliac muscle is trapped between the iliopsoas tendon and the pubic bone during the abduction–flexion–external rotation movement. As the hip is brought back to the neutral position, the iliopsoas tendon abruptly rolls over the iliac muscle to snap on the pubic bone instead of gliding back smoothly medially over the muscle to end its course on the pubic bone without a snap in the normal hip [2]. Winston et al. [19] described a mechanism in a small subgroup of their patients in which the iliopsoas tendon becomes imbedded in the muscle, snapping back and forth during hip motion. We did not see this type of snapping process in our study, although it shares similarities with our findings and may represent a variant. This suggests that the snapping iliopsoas tendon may consist of a spectrum of clinical situations in which the tendon may become imbedded within or roll more completely over the iliac muscle during lateral hip motion. We postulate that a bulky poorly compressible muscle confined in a tight fascia is needed for the psoas tendon to roll over. Interestingly, fasciotomy has been used as an efficient surgical treatment instead of iliopsoas tendon lengthening [21]. Documentation of this new iliopsoas tendon snapping mechanism may help orient appropriate therapy [6, 20].

Five patients had signs of tendinosis. Repetitive snapping of the tendon onto the bone may predispose to tendinopathy. Two patients had an anatomic variant with bifid iliopsoas tendons and snapping due to flipping of these two tendons on one another. To our knowledge, this cause of snapping hip has not been reported previously. Although the exact prevalence of this variant is unknown, in an anatomic study of 24 hips, Tatu et al. [18] found two split and two partially split iliopsoas tendons. This variant was identified in four of the 28 hips examined in our study.

In one patient, snapping was provoked by the iliopsoas tendon impinging on a paralabral cyst. This type of snapping mechanism of the iliopsoas tendon—that is, snapping associated with paralabral cysts—has been previously reported [12, 22].

A limitation of our study is the small number of patients. Evaluation of a larger cohort may include documented cases of bone impingement, as has been reported in the literature. However, our study suggests that bone structures are usually not involved in most snapping hips.

In conclusion, we describe new snapping iliopsoas tendon mechanisms using dynamic sonography. An unusual dynamic relationship between the psoas tendon and its muscle was the more common cause.

References

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This Article Abstract Figures Only Full Text (PDF) MOVIES Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Deslandes, M. Articles by Bureau, N. J. Search for Related Content PubMed PubMed Citation Articles by Deslandes, M. Articles by Bureau, N. J. Social Bookmarking                      What's this? Hotlight (NEW!) What's Hotlight?