Musculoskeletal Imaging Review Kassarjian et al. MRI of the Quadratus Femoris Musculoskeletal Imaging Review Ara Kassarjian 1 Xavier Tomas 2 Luis Cerezal 3 Ana Canga 4,5 Eva Llopis 6 Kassarjian A, Tomas X, Cerezal L, Canga A, Llopis E Keywords: anatomy, hip, impingement, MRI, muscle, quadratus femoris DOI:10.2214/AJR.10.5898 Received October 4, 2010; accepted after revision November 18, 2010. 1 Department of Musculoskeletal Radiology, Corades, S.L., (28220 Majadahonda), Madrid, Spain. Address correspondence to A. Kassarjian (akassarjian@gmail.com). 2 Musculoskeletal Unit, Department of Radiology, Hospital Clinic, Barcelona, Catalonia, Spain. 3 Diagnóstico Médico Cantabria, Santander, Cantabria, Spain. 4 Department of Radiology, Marqués de Valdecilla University Hospital, Santander, Cantabria, Spain. 5 Department of Anatomy and Cellular Biology, University of Cantabria, Santander, Cantabria, Spain. 6 Department of Radiology, Hospital de la Ribera, Alzira, Valencia, Spain. AJR 2011; 197:170 174 0361 803X/11/1971 170 American Roentgen Ray Society MRI of the Quadratus Femoris Muscle: Anatomic Considerations and Pathologic Lesions OBJECTIVE. The purpose of this review is to describe the gross anatomic and MRI appearance of the quadratus femoris muscle and the MRI appearance of common lesions of the quadratus femoris. CONCLUSION. Lesions of the quadratus femoris have been implicated as a cause of hip pain. It therefore is important to be familiar with the anatomy of the quadratus muscle and to be able to diagnose the causes of abnormal signal intensity in the quadratus femoris, which include tears and impingement. Background Because of the ever-increasing use of MRI, with or without MR arthrography, in the evaluation of hip pain, radiologists must be aware of subtle and less common abnormalities that mimic both intraarticular and extraarticular hip disease. Lesions of the quadratus femoris muscle have been implicated as a cause of hip pain [1 6]. It therefore is important to be familiar with the normal anatomy of the quadratus muscle and to be able to accurately diagnose the cause of abnormal signal intensity in the muscle. Gross Anatomy The quadratus femoris muscle is situated along the posterior aspect of the hip joint and, as the name suggests, has a quadrangular, somewhat rectangular, appearance. Its origin is at the inferolateral margin of the ischium along the anterior portion of the ischial tuberosity just anterior to the origin of the hamstring tendons. Its insertion is along the posterior medial aspect of the proximal femur along the quadrate tubercle of the posterior intertrochanteric ridge (Figs. 1 3). The muscle has a somewhat striated appearance, the fibers running along the horizontal (axial) plane. The fibers are more closely opposed along the femoral end of the muscle, are more loosely arranged, and have more interspersed fat along the ischial aspect. Along its anterior aspect, the quadratus femoris is bordered by the obturator externus muscle; along its posterior aspect it is bordered by fat and the sciatic nerve (Fig. 4 7). Along its su- perior aspect, the quadratus femoris is bordered by fat and the inferior gemellus; along its inferior aspect, it is bordered by the adductor magnus. Innervation and Function The quadratus femoris muscle acts as an adductor and external rotator of the hip. It is innervated by a small branch off the sacral plexus. Specifically, it derives its innervation from the L4, L5, and S1 spinal nerves. The nerve to the quadratus femoris muscle exits the pelvis through the greater sciatic notch, travels inferiorly along the anterior border of the gemellus and obturator internus muscles, and enters the quadratus muscle along its anterior surface. This same nerve can give rise to a small articular branch. MRI Anatomy The quadratus femoris muscle is easily identified on axial, sagittal, and, depending on slice thickness, coronal images of the hip. The muscle is often best evaluated on axial images, on which the origin, insertion, and anterior and posterior relations can be evaluated (Figs. 2 and 3). The tendinous origin along the ischium can appear broad based and fasciculated and is best located by searching along the ischial tuberosity just anterior to the hamstring tendons. The insertion of the quadratus femoris muscle onto the posteromedial femur is characterized by a convergence of muscle fibers toward a narrower attachment compared with that of the origin (Figs. 2, 3, 5, and 6). The hamstring 170 AJR:197, July 2011
MRI of the Quadratus Femoris tendons are just posterior to the quadratus femoris origin and the sciatic nerve along the posterior margin of the quadratus femoris muscle. Sagittal images can show these same relations and the inferior gemellus along the superior aspect and the sciatic nerve along the posterior aspect (Fig. 7). Injuries and MRI Signal-Intensity Abnormalities of the Quadratus Femoris Muscle Lesions of the quadratus femoris muscle have not been reported with great frequency in the English radiologic literature. According to the literature, the most common primary lesions of the quadratus femoris are myotendinous strains, or partial tears, of the quadratus femoris and impingement of the belly of the quadratus femoris [3, 4]. Certain lesions of the quadratus femoris muscle, such as impingement, appear to be more common in middle-aged and older women and typically become evident as posterior gluteal hip pain or groin pain with or without a clear inciting event. The pain can radiate along the posterior thigh, possibly because of irritation of the closely apposed sciatic nerve, which travels along the posterior aspect of the muscle. As with most muscle strains in other parts of the body, strain of the quadratus femoris muscle appears as edema centered along the myotendinous junction of the quadratus femoris muscle with or without associated fluid. This finding is most commonly seen along the distal myotendinous junction along the posteromedial aspect of the proximal femur. Strains of the quadratus femoris are best seen on axial and sagittal fat-suppressed fluid-sensitive images obtained with STIR, fat-suppressed proton density weighted, or fat-suppressed T2-weighted sequences (Fig. 8). On axial and sagittal images, tears can become evident as edema and fluid posterior to the lesser trochanter. The entity of impingement of the quadratus femoris muscle, first described by Kassarjian [4] in three patients, is visualized as crowding of the fibers of the muscle belly in the space between the ischium or hamstring tendons and the posteromedial femur. Subsequent reports described similar cases and confirmed the association between impingement of the quadratus femoris muscle and hip pain. The edema associated with impingement of the muscle is typically centered in the muscle belly at the site of maximal impingement (Figs. 9 and 10). This finding is in contradistinction to the edema in myotendinous strains, which is typically seen along the distal myotendinous junction. Impingement of the quadratus femoris muscle is best assessed on axial images, on which the location of the edema can be accurately localized. In addition, axial images facilitate assessment of the relation between the muscle belly and the surrounding structures. Although muscle fiber orientation can be seen on fatsuppressed images, the orientation is typically better seen on images without fat suppression. Torriani et al. [6] attempted to correlate a narrowed distance between the ischial tuberosity and the lesser trochanter and impingement of the quadratus femoris. However, because of small sample size and lack of control for degree of hip rotation at imaging, the validity of such measurements remains unclear. Although at first glance it may be difficult to differentiate strain and impingement, careful analysis of the location of edema and the configuration of the muscle fibers and surrounding structures can aid in differentiating the two entities. Other entities can affect the quadratus femoris. There have been case reports of tendinitis of the quadratus femoris presenting as hip pain [2]. In addition, denervation of the quadratus femoris (Fig. 11) can occur in the absence of a tear, which is presumed to be the result of an injury or lesion of the neural branch from the sacral plexus that innervates the quadratus femoris. In addition, areas of abnormal signal intensity (e.g., due to edema) can be seen after new or intense activities (Fig. 12). Although with imaging alone the findings can resemble mild acute (partial) tears, the lack of muscle fiber disruption and the clinical history often can help differentiate acute partial tear from exercise-induced edema, such as delayed-onset muscle soreness. If substantial edema or fluid is present in the region, the findings can mimic those of other entities. For instance, if bone marrow edema or proliferative change is present in the lesser trochanter or ischial tuberosity, the findings can mimic a primary osseous abnormality or osseous abnormality secondary to iliopsoas tendon or hamstring tendon abnormalities. If a substantial amount of fluid is found (rare in our experience), the findings can theoretically mimic iliopsoas bursitis if the fluid is near the lesser trochanter and mimic ischial bursitis if the fluid is near the ischial tuberosity. Careful analysis of the images and scrutiny of the actual location of fluid and edema and local muscle and tendon anatomy typically aids differentiation of these entities. Conclusion MRI can elegantly depict the normal anatomy and pathologic conditions of the quadratus femoris muscle. Strain and impingement are the two most common primary lesions of this muscle. These two entities can be differentiated at MRI by careful analysis of the location of edema and the configuration of the muscle fibers. References 1. Klinkert P Jr, Porte RJ, de Rooij TP, de Vries AC. Quadratus femoris tendinitis as a cause of groin pain. Br J Sports Med 1997; 31:348 349 2. Peltola K, Heinonen OJ, Orava S, Mattila K. Quadratus femoris muscle tear: an uncommon cause for radiating gluteal pain. Clin J Sport Med 1999; 9:228 230 3. O Brien SD, Bui-Mansfield LT. MRI of quadratus femoris muscle tear: another cause of hip pain. AJR 2007; 189:1185 1189 4. Kassarjian A. Signal abnormalities in the quadratus femoris muscle: tear or impingement? (letter). AJR 2008; 190:[web]W379 5. Patti JW, Ouellette H, Bredella MA, Torriani M. Impingement of lesser trochanter on ischium as a potential cause for hip pain. Skeletal Radiol 2008; 37:939 941 6. Torriani M, Souto SC, Thomas BJ, Ouellette H, Bredella MA. Ischiofemoral impingement syndrome: an entity with hip pain and abnormalities of the quadratus femoris muscle. AJR 2009; 193:186 190 AJR:197, July 2011 171
Kassarjian et al. Fig. 1 Cadaver of 69-year-old man with normal anatomy of quadratus femoris muscle. Photograph shows axial gross anatomic relations. Single arrow indicates origin of quadratus femoris; arrowhead, insertion; asterisk, obturator externus muscle; oval, sciatic nerve; double arrow, hamstring origin. I = ischial tuberosity, QF = quadratus femoris, F = femur. Fig. 3 13-year-old girl with left hip pain and normal hip arthrogram and normal anatomy of quadratus femoris muscle. Axial T1-weighted clinical MR image shows anatomic relations. Asterisk indicates obturator externus muscle; arrow, origin of quadratus femoris muscle; oval, sciatic nerve; double arrow, hamstring origin; arrowhead: insertion of quadratus femoris muscle. F = femur, QF = quadratus femoris, I = ischial tuberosity. Fig. 2 Cadaver of 69-year-old man with normal anatomy of quadratus femoris muscle. Axial T1-weighted MR image shows anatomic relations. Asterisk indicates obturator externus muscle; arrow, origin; oval, sciatic nerve; double arrows, hamstring origin; arrowhead, insertion. QF = quadratus femoris, I = ischial tuberosity, F = femur. Fig. 4 Cadaver of 69-year-old man with normal anatomy of quadratus femoris muscle. Photograph shows coronal gross anatomy. Arrow indicates inferior gemellus muscle. I = ischium, QF = quadratus femoris, F = femur. 172 AJR:197, July 2011
MRI of the Quadratus Femoris Fig. 5 Cadaver of 69-year-old man with normal anatomy of quadratus femoris muscle. Coronal T1-weighted MR image shows anatomic relations. Arrow indicates inferior gemellus muscle. QF = quadratus femoris, I = ischium, F = femur. Fig. 7 13-year-old girl with left hip pain and normal hip arthrogram and normal anatomy of quadratus femoris muscle. Sagittal T2-weighted clinical MR images from medial to lateral show origin (QF1), belly (QF2), and insertion (QF3) of quadratus femoris muscle. Arrow indicates inferior gemellus muscle; arrowheads, sciatic nerve. I = ischium, H = hamstring origin. Fig. 6 13-year-old girl with left hip pain and normal hip arthrogram and normal anatomy of quadratus femoris muscle. Coronal T1-weighted clinical MR image shows anatomic relations. Arrow indicates inferior gemellus muscle. I = ischium, F= femur, QF = quadratus femoris. Fig. 8 13-year-old girl with right hip pain. Axial fat-suppressed T2-weighted MR image shows tear (grade 2 strain) (arrow). Tears appear to be more frequent near femoral end of muscle. F = femur, I = ischium. AJR:197, July 2011 173
Kassarjian et al. Fig. 9 73-year-old woman with right posterior hip and buttock pain and impingement of quadratus femoris. Axial T1-weighted (left) and fat-suppressed T2-weighted (right) MR images show crowding of fibers and edema in fibers (arrow) of quadratus femoris. These are typical findings of impingement of quadratus femoris. Oval indicates sciatic nerve. F = femur, I = ischium. Fig. 11 26-year-old woman with asymptomatic atrophy of quadratus femoris (QF) muscle. Axial T1-weighted MR image shows complete atrophy of quadratus femoris. Asterisk indicates obturator externus muscle; oval, sciatic nerve; arrowhead, intact quadratus femoris tendon insertion; double arrow, hamstring origin. F = femur, I = ischium. Fig. 10 20-year-old man with right hip pain and impingement of quadratus femoris muscle. Axial T1-weighted (left) and fat-suppressed T2-weighted (right) images show crowding of fibers and edema in fibers (arrows) of quadratus femoris muscle. These findings are typical in impingement of quadratus femoris. Oval indicates sciatic nerve. F = femur, I = ischium. Fig. 12 25-year-old woman with exercise-induced edema of quadratus femoris muscle. Progressive buttock pain and sciatica occurred after patient began new exercise regimen consisting of intensive spinning (stationary cycling) classes. A C, Coronal (A) and sagittal (B and C) fat-suppressed proton density weighted MR images show area of increased signal intensity (arrows) in both quadratus femoris muscles, right greater than left. 174 AJR:197, July 2011