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Iliotibial Band Friction Syndrome: MR Imaging Findings in 16 Patients and MR Arthrographic Study of Six Cadaveric Knees¹

¹ From the Depts of Radiology (C.M., J.M.A., L.R.Y., D.J.T., D.R.) and Pathology (P.H.), Veterans Affairs Medical Center, 3350 La Jolla Village Dr, San Diego, CA 92161; Dept of Diagnostic Radiology, University of Kiel, Germany (C.M.); Dept of Radiology, Stanford University, Calif (G.A.B.); Dept of Radiology, Beth Israel Deaconess Medical Center, Boston, Mass (R.D.B.); Dept of Radiology, Thomas Jefferson Hospital, Philadelphia, Pa (M.S.); and Dept of Diagnostic Radiology, Henry Ford Hospital, Detroit, Mich (J.A.J.). Received May 1, 1998; revision requested Jul 6; final revision received Jan 22, 1999; accepted Jan 27. Supported in part by the Deutsche Forschungsgemeinschaft and Veterans Administration grant SA360. Address reprint requests to D.R.

	Abstract

TOP Abstract Introduction MATERIALS AND METHODS RESULTS DISCUSSION References

 
PURPOSE: To define magnetic resonance (MR) imaging findings in patients with the iliotibial band friction syndrome (ITBFS) and to correlate these findings with anatomic features defined at magnetic resonance (MR) arthrography in cadavers.

MATERIALS AND METHODS: The anatomic relationship of the iliotibial tract (ITT) to the lateral recesses of the knee joint and the lateral femoral epicondyle was investigated with MR arthrography at full extension and at 30° and 60° of knee flexion in six cadaveric knees. Seventeen MR imaging studies in 16 patients with ITBFS were evaluated.

RESULTS: In the cadaveric study, no interference of the lateral synovial recess with the lateral femoral epicondyle at full extension and at 30° and 60° of knee flexion was observed. In all specimens, correlation of MR images with macroscopic and microscopic sections revealed no primary bursa between the lateral femoral epicondyle and the ITT. In clinical studies, MR imaging findings of poorly defined signal intensity abnormalities or circumscribed fluid collections were located in a compartmentlike space confined laterally by the ITT and medially by the meniscocapsular junction, the lateral collateral ligament, and the lateral femoral epicondyle.

CONCLUSION: MR imaging accurately depicts the compartmentlike distribution of signal intensity abnormalities in patients with ITBFS.

Index terms: Athletic injuries, 452.485 • Iliotibial tract, 452.92 • Joints, MR, 452.121411, 452.121412, 452.121415 • Knee, injuries, 452.485 • Knee, ligaments, menisci, and cartilage, 452.485, 452.92 • Knee, MR, 452.121411, 452.121412, 452.121415 • Magnetic resonance (MR), arthrography, 452.122

	Introduction

TOP Abstract Introduction MATERIALS AND METHODS RESULTS DISCUSSION References

 
Iliotibial band friction syndrome (ITBFS) is a common cause of lateral knee pain that is often related to intense physical activity, as occurs in long-distance runners, cyclists, and American football players (1–6). The diagnosis of ITBFS is based on clinical examination, with tenderness over the lateral femoral epicondyle and reproducible pain during flexion and extension of the knee while the examiner exerts pressure over the lateral femoral epicondyle (7). In some patients, however, ITBFS can be misdiagnosed as some other derangement of the knee, such as a lateral meniscal tear, lateral collateral ligament sprain, popliteal tendon strain, or lateral hamstring strain (3). Although repetitive friction of the iliotibial tract (ITT) over the lateral femoral epicondyle at 30° of knee flexion is described as the main cause of ITBFS, no study, to our knowledge, has yet evaluated the relation of the ITT and the lateral femoral epicondyle during the critical range of knee motion between full extension and 60° of flexion.

The ITT is formed proximally at the level of the greater trochanter by the coalescence of the fascial investments of the tensor fasciae latae, the gluteus maximus muscle, and the gluteus medius muscle (Fig 1). Proximal to the knee joint, the ITT is attached to the supracondylar tubercle of the femoral condyle and the intermuscular septum, and it continues distally to attach to the Gerdy tubercle at the anterolateral aspect of the tibia (8,9). Proximal to the lateral femoral epicondyle, the ITT is separated from the femur by a wide layer of fatty tissue that extends to the vastus lateralis muscle.

View larger version (38K): [in this window] [in a new window]   Figure 1. Drawing of the normal anatomy of the ITT as seen from the lateral aspect of the thigh.

View larger version (24K): [in this window] [in a new window]   Figure 2. Drawing of the relationship of the ITT to the lateral epicondyle, the lateral collateral ligament, and the lateral recess of the knee joint in the axial plane.

The purpose of our study was to describe the characteristic MR imaging findings in patients with ITBFS and to investigate the anatomic relationship of the ITT and the lateral femoral epicondyle during knee flexion by using MR arthrography in cadavers.

	MATERIALS AND METHODS

TOP Abstract Introduction MATERIALS AND METHODS RESULTS DISCUSSION References

 
Six human legs with preserved hemipelves were obtained from nonembalmed fresh cadavers (four men, two women; age range, 72–86 years at the time of death; mean age, 75 years) and were immediately deep-frozen at -40°C (Forma Bio-Freezer; Forma Scientific, Marietta, Ohio). The specimens were allowed to thaw for 24 hours at room temperature prior to imaging. All specimens were examined with routine radiography to exclude those with previous injuries.

MR images were obtained with a 1.5-T superconducting MR imager (Signa; GE Medical Systems, Milwaukee, Wis). The specimens were positioned supine inside a receive-only knee coil at full extension and at 30° and 60° of knee flexion by using precisely angled wooden bars. These angle positions were chosen because prior clinical studies (9,10) described the occurrence of ITBFS in knee positions that ranged from full extension to 60° of flexion. To determine the relation of the lateral synovial recess to the lateral femoral epicondyle during knee flexion, 60 mL of a 2 mmol/L gadopentetate dimeglumine solution (Magnevist [1 mL in 250 mL saline solution]; Schering, Berlin, Germany) was injected intraarticularly to simulate a joint effusion, following the protocol described by Engel (14). Gadolinium-enhanced MR arthrography was performed with T1-weighted spin-echo imaging in the axial and coronal planes. Images were acquired in both planes because of prior documentation that both are useful in the assessment of the ITT (6,7). The imaging parameters are listed in Table 1.

In addition, MR imaging studies of 16 patients (six male patients, 10 female patients; age range, 17–54 years; mean age, 35 years) with ITBFS were obtained from five institutions and were analyzed. In each patient, available history and results of physical examination performed by one or more orthopedic surgeons provided evidence consistent with ITBFS. All patients were treated conservatively without surgical intervention.

All MR images were obtained with the knee placed supine and in extension inside a receive-only knee coil. The MR examinations were performed by using 1.0- or 1.5-T magnets (Signa, GE Medical Systems; Magnetom Expert, Siemens Medical Systems, Iselin, NJ) with the following sequences: fat-saturated T2-weighted fast spin-echo sequence, T1-weighted spin-echo sequence, T2*-weighted two-dimensional multiplanar gradient-recalled-echo sequence, and three-dimensional double-echo steady state sequence. The MR imaging protocol is summarized in Table 1.

The MR images were evaluated by consensus by two radiologists (C.M., J.M.A.) experienced in musculoskeletal imaging who used the following criteria (7,12,13): (a) poorly defined signal intensity abnormalities lateral, distal, or proximal to the lateral epicondyle; (b) signal intensity abnormalities superficial or deep to the ITT; (c) localized fluid collection lateral, distal, or proximal to the lateral epicondyle; (d) width of the ITT at the level of the lateral epicondyle; (e) joint effusion; and (f) additional findings (eg, meniscal tears).

To compare the width of the ITT in patients with that in a control group, 20 healthy subjects (10 male subjects, 10 female subjects; age range, 15–63 years; mean age, 37 years) were examined with the knee placed supine and in extension inside a receive-only knee coil by using a coronal T1-weighted spin-echo sequence (550/18 [repetition time msec/echo time msec]) with a 4-mm section thickness. The Student t test was used to evaluate statistically significant differences with regard to the width of the ITT between patients and healthy subjects. Significant results were assumed on the 5% level (P < .05).

	RESULTS

TOP Abstract Introduction MATERIALS AND METHODS RESULTS DISCUSSION References

 
Cadaveric Study
The ITT, the lateral collateral ligament, the popliteus tendon, and the insertion of the tendon of the biceps femoris muscle demonstrated complex anatomic interrelationships. The relationships among the ITT, the lateral synovial recess, and the lateral femoral epicondyle were visualized best on axial MR images. At extension, in this imaging plane, contact of the posterior fibers of the ITT with the lateral femoral epicondyle and the inserting fibers of the lateral collateral ligament was observed in four (66%) of six specimens. In two (33%) of six specimens, however, the ITT was located anterior to the femoral insertions of the popliteus tendon and the lateral collateral ligament. With further flexion, in all specimens the ITT moved posteriorly and came in contact with the lateral femoral epicondyle and the inserting fibers of the lateral collateral ligament below this epicondyle (Fig 3).

View larger version (153K): [in this window] [in a new window]   Figure 3a. Axial images of a specimen obtained at extension and at 30° and 60° of knee flexion after intraarticular injection of contrast material. For a–c, arrowheads = ITT, black arrow = lateral femoral epicondyle, curved white arrow = lateral collateral ligament, straight white arrow = lateral recess. (a) T1-weighted spin-echo MR image (600/20) obtained after the intraarticular administration of gadopentetate dimeglumine shows the close relationship of the posterior fibers of the ITT to the lateral femoral epicondyle and the fibers of the lateral collateral ligament at full extension. (b) T1-weighted spin-echo MR image (600/20) shows 30° of knee flexion. (c) T1-weighted spin-echo MR image (600/20) shows that at 60° of knee flexion the ITT moves posteriorly and comes in contact with the lateral femoral epicondyle and the inserting fibers of the lateral collateral ligament. At extension and at 30° and 60° of knee flexion, the lateral recess extends anterior to the lateral femoral epicondyle. (d) Photograph of the corresponding macroscopic section reveals prominent inserting fibers of the lateral collateral ligament (curved white arrow) distal to the lateral femoral epicondyle (black arrow) in close proximity to the ITT (arrowheads). Straight white arrow = lateral recess, open arrow = popliteus tendon. (e) Photomicrograph shows layers of fatty tissue and vessels between the lateral femoral epicondyle (curved arrow) and the ITT (arrowheads). No bursa is identified. The lateral recess (straight arrow) extends anterior to the lateral femoral epicondyle (curved arrow). (Hematoxylin-eosin stain; original magnification, x4.)

View larger version (156K): [in this window] [in a new window]   Figure 3b. Axial images of a specimen obtained at extension and at 30° and 60° of knee flexion after intraarticular injection of contrast material. For a–c, arrowheads = ITT, black arrow = lateral femoral epicondyle, curved white arrow = lateral collateral ligament, straight white arrow = lateral recess. (a) T1-weighted spin-echo MR image (600/20) obtained after the intraarticular administration of gadopentetate dimeglumine shows the close relationship of the posterior fibers of the ITT to the lateral femoral epicondyle and the fibers of the lateral collateral ligament at full extension. (b) T1-weighted spin-echo MR image (600/20) shows 30° of knee flexion. (c) T1-weighted spin-echo MR image (600/20) shows that at 60° of knee flexion the ITT moves posteriorly and comes in contact with the lateral femoral epicondyle and the inserting fibers of the lateral collateral ligament. At extension and at 30° and 60° of knee flexion, the lateral recess extends anterior to the lateral femoral epicondyle. (d) Photograph of the corresponding macroscopic section reveals prominent inserting fibers of the lateral collateral ligament (curved white arrow) distal to the lateral femoral epicondyle (black arrow) in close proximity to the ITT (arrowheads). Straight white arrow = lateral recess, open arrow = popliteus tendon. (e) Photomicrograph shows layers of fatty tissue and vessels between the lateral femoral epicondyle (curved arrow) and the ITT (arrowheads). No bursa is identified. The lateral recess (straight arrow) extends anterior to the lateral femoral epicondyle (curved arrow). (Hematoxylin-eosin stain; original magnification, x4.)

View larger version (144K): [in this window] [in a new window]   Figure 3c. Axial images of a specimen obtained at extension and at 30° and 60° of knee flexion after intraarticular injection of contrast material. For a–c, arrowheads = ITT, black arrow = lateral femoral epicondyle, curved white arrow = lateral collateral ligament, straight white arrow = lateral recess. (a) T1-weighted spin-echo MR image (600/20) obtained after the intraarticular administration of gadopentetate dimeglumine shows the close relationship of the posterior fibers of the ITT to the lateral femoral epicondyle and the fibers of the lateral collateral ligament at full extension. (b) T1-weighted spin-echo MR image (600/20) shows 30° of knee flexion. (c) T1-weighted spin-echo MR image (600/20) shows that at 60° of knee flexion the ITT moves posteriorly and comes in contact with the lateral femoral epicondyle and the inserting fibers of the lateral collateral ligament. At extension and at 30° and 60° of knee flexion, the lateral recess extends anterior to the lateral femoral epicondyle. (d) Photograph of the corresponding macroscopic section reveals prominent inserting fibers of the lateral collateral ligament (curved white arrow) distal to the lateral femoral epicondyle (black arrow) in close proximity to the ITT (arrowheads). Straight white arrow = lateral recess, open arrow = popliteus tendon. (e) Photomicrograph shows layers of fatty tissue and vessels between the lateral femoral epicondyle (curved arrow) and the ITT (arrowheads). No bursa is identified. The lateral recess (straight arrow) extends anterior to the lateral femoral epicondyle (curved arrow). (Hematoxylin-eosin stain; original magnification, x4.)

View larger version (181K): [in this window] [in a new window]   Figure 3d. Axial images of a specimen obtained at extension and at 30° and 60° of knee flexion after intraarticular injection of contrast material. For a–c, arrowheads = ITT, black arrow = lateral femoral epicondyle, curved white arrow = lateral collateral ligament, straight white arrow = lateral recess. (a) T1-weighted spin-echo MR image (600/20) obtained after the intraarticular administration of gadopentetate dimeglumine shows the close relationship of the posterior fibers of the ITT to the lateral femoral epicondyle and the fibers of the lateral collateral ligament at full extension. (b) T1-weighted spin-echo MR image (600/20) shows 30° of knee flexion. (c) T1-weighted spin-echo MR image (600/20) shows that at 60° of knee flexion the ITT moves posteriorly and comes in contact with the lateral femoral epicondyle and the inserting fibers of the lateral collateral ligament. At extension and at 30° and 60° of knee flexion, the lateral recess extends anterior to the lateral femoral epicondyle. (d) Photograph of the corresponding macroscopic section reveals prominent inserting fibers of the lateral collateral ligament (curved white arrow) distal to the lateral femoral epicondyle (black arrow) in close proximity to the ITT (arrowheads). Straight white arrow = lateral recess, open arrow = popliteus tendon. (e) Photomicrograph shows layers of fatty tissue and vessels between the lateral femoral epicondyle (curved arrow) and the ITT (arrowheads). No bursa is identified. The lateral recess (straight arrow) extends anterior to the lateral femoral epicondyle (curved arrow). (Hematoxylin-eosin stain; original magnification, x4.)

View larger version (196K): [in this window] [in a new window]   Figure 3e. Axial images of a specimen obtained at extension and at 30° and 60° of knee flexion after intraarticular injection of contrast material. For a–c, arrowheads = ITT, black arrow = lateral femoral epicondyle, curved white arrow = lateral collateral ligament, straight white arrow = lateral recess. (a) T1-weighted spin-echo MR image (600/20) obtained after the intraarticular administration of gadopentetate dimeglumine shows the close relationship of the posterior fibers of the ITT to the lateral femoral epicondyle and the fibers of the lateral collateral ligament at full extension. (b) T1-weighted spin-echo MR image (600/20) shows 30° of knee flexion. (c) T1-weighted spin-echo MR image (600/20) shows that at 60° of knee flexion the ITT moves posteriorly and comes in contact with the lateral femoral epicondyle and the inserting fibers of the lateral collateral ligament. At extension and at 30° and 60° of knee flexion, the lateral recess extends anterior to the lateral femoral epicondyle. (d) Photograph of the corresponding macroscopic section reveals prominent inserting fibers of the lateral collateral ligament (curved white arrow) distal to the lateral femoral epicondyle (black arrow) in close proximity to the ITT (arrowheads). Straight white arrow = lateral recess, open arrow = popliteus tendon. (e) Photomicrograph shows layers of fatty tissue and vessels between the lateral femoral epicondyle (curved arrow) and the ITT (arrowheads). No bursa is identified. The lateral recess (straight arrow) extends anterior to the lateral femoral epicondyle (curved arrow). (Hematoxylin-eosin stain; original magnification, x4.)

At microscopic inspection, the layer of high signal intensity between the ITT and lateral femoral epicondyle represented fatty and vascular tissue with no evidence of a bursa (Fig 3e). The synovial lining of the lateral recess was found in all specimens to extend anterior and proximal to the lateral femoral epicondyle, without any contact with the lateral femoral epicondyle.

Clinical Study
The clinical findings in 16 patients with ITBFS are summarized in Table 2. Poorly defined MR signal intensity abnormalities lateral, proximal, or distal to the lateral femoral epicondyle were found in 12 (75%) of 16 patients (Table 3). On coronal images, signal intensity changes were observed deep to the ITT proximal to the lateral femoral epicondyle in the fatty layer extending distal to the vastus lateralis muscle (Figs 4–6). On axial images, in four (23%) of 17 knees signal intensity abnormalities were located in the posterolateral aspect of the knee joint, in an area confined by the biceps femoris muscle and the femoral shaft. In six (35%) of 17 knees, signal intensity alterations were found distal to the lateral femoral epicondyle, bounded medially by the lateral collateral ligament and the meniscocapsular junction and laterally by the ITT. The ITT demonstrated normal signal intensity on all MR images. Signal intensity abnormalities were accompanied by a joint effusion in five (29%) of 17 knees and by meniscal tears in three (18%) of 17 knees. In the patient group, the mean width of the ITT at the level of the lateral femoral epicondyle was 2.3 mm ± 0.54 (1 SD). In comparison, the width of the ITT in healthy subjects was 2.0 mm ± 0.46 (1 SD). The difference in measurements between the two groups was not significant (P = .8).

View larger version (64K): [in this window] [in a new window]   Figure 4. Drawing of the compartmentlike space in which signal intensity changes can be observed on coronal MR images in patients with ITBFS. The signal intensity abnormalities are located in the confines of a space demarcated laterally by the ITT and distally and medially by the meniscocapsular ligaments, the lateral meniscus, and the lateral femoral epicondyle. Proximal to the lateral femoral epicondyle, the signal intensity alterations extend into the fatty tissue distal to the vastus lateralis muscle.

View larger version (187K): [in this window] [in a new window]   Figure 5a. Patient 10. Images obtained in a 17-year-old soccer player with lateral knee pain for 6 weeks. (a) Coronal T2-weighted fat-saturated fast spin-echo MR image (4,400/108, 4-mm section thickness) reveals poorly defined high-signal-intensity alterations (straight arrows) medial to the ITT (arrowheads) that extend into the fatty layer distal to the vastus lateralis muscle (curved arrow). (b) Corresponding axial T2-weighted fat-saturated fast spin-echo MR image (4,400/108, 4-mm section thickness) demonstrates soft-tissue edema (arrows) between the ITT (arrowheads) and the femur.

View larger version (183K): [in this window] [in a new window]   Figure 5b. Patient 10. Images obtained in a 17-year-old soccer player with lateral knee pain for 6 weeks. (a) Coronal T2-weighted fat-saturated fast spin-echo MR image (4,400/108, 4-mm section thickness) reveals poorly defined high-signal-intensity alterations (straight arrows) medial to the ITT (arrowheads) that extend into the fatty layer distal to the vastus lateralis muscle (curved arrow). (b) Corresponding axial T2-weighted fat-saturated fast spin-echo MR image (4,400/108, 4-mm section thickness) demonstrates soft-tissue edema (arrows) between the ITT (arrowheads) and the femur.

View larger version (156K): [in this window] [in a new window]   Figure 6a. Patient 9. Images obtained in a 20-year-old freehand rock climber with tenderness and pain over the lateral femoral epicondyle. (a) Coronal T1-weighted spin-echo MR image (550/18, 4-mm section thickness) shows poorly defined low-signal-intensity changes (straight arrows) medial to the ITT (arrowheads) and distal to the vastus lateralis muscle (curved arrow). (b) Corresponding coronal two-dimensional multiplanar gradient-recalled-echo image (600/15, 4-mm section thickness, 30° flip angle) shows high-signal-intensity alterations (arrows) that correspond to the low-signal-intensity changes in a. Arrowheads = ITT. (c) Axial T2-weighted fat-saturated fast spin-echo MR image (4,400/108, 4-mm section thickness) shows abnormal signal intensity alterations (white arrow) lateral to the lateral femoral epicondyle (black arrow). Arrowhead = ITT. (d) Axial T2-weighted fat-saturated fast spin-echo MR image (4,400/108, 4-mm section thickness) shows abnormal signal intensity alterations (solid arrows) medial to the ITT (arrowhead), adjacent to the biceps femoris muscle (open arrow) and femur.

View larger version (179K): [in this window] [in a new window]   Figure 6c. Patient 9. Images obtained in a 20-year-old freehand rock climber with tenderness and pain over the lateral femoral epicondyle. (a) Coronal T1-weighted spin-echo MR image (550/18, 4-mm section thickness) shows poorly defined low-signal-intensity changes (straight arrows) medial to the ITT (arrowheads) and distal to the vastus lateralis muscle (curved arrow). (b) Corresponding coronal two-dimensional multiplanar gradient-recalled-echo image (600/15, 4-mm section thickness, 30° flip angle) shows high-signal-intensity alterations (arrows) that correspond to the low-signal-intensity changes in a. Arrowheads = ITT. (c) Axial T2-weighted fat-saturated fast spin-echo MR image (4,400/108, 4-mm section thickness) shows abnormal signal intensity alterations (white arrow) lateral to the lateral femoral epicondyle (black arrow). Arrowhead = ITT. (d) Axial T2-weighted fat-saturated fast spin-echo MR image (4,400/108, 4-mm section thickness) shows abnormal signal intensity alterations (solid arrows) medial to the ITT (arrowhead), adjacent to the biceps femoris muscle (open arrow) and femur.

View larger version (194K): [in this window] [in a new window]   Figure 6b. Patient 9. Images obtained in a 20-year-old freehand rock climber with tenderness and pain over the lateral femoral epicondyle. (a) Coronal T1-weighted spin-echo MR image (550/18, 4-mm section thickness) shows poorly defined low-signal-intensity changes (straight arrows) medial to the ITT (arrowheads) and distal to the vastus lateralis muscle (curved arrow). (b) Corresponding coronal two-dimensional multiplanar gradient-recalled-echo image (600/15, 4-mm section thickness, 30° flip angle) shows high-signal-intensity alterations (arrows) that correspond to the low-signal-intensity changes in a. Arrowheads = ITT. (c) Axial T2-weighted fat-saturated fast spin-echo MR image (4,400/108, 4-mm section thickness) shows abnormal signal intensity alterations (white arrow) lateral to the lateral femoral epicondyle (black arrow). Arrowhead = ITT. (d) Axial T2-weighted fat-saturated fast spin-echo MR image (4,400/108, 4-mm section thickness) shows abnormal signal intensity alterations (solid arrows) medial to the ITT (arrowhead), adjacent to the biceps femoris muscle (open arrow) and femur.

View larger version (190K): [in this window] [in a new window]   Figure 6d. Patient 9. Images obtained in a 20-year-old freehand rock climber with tenderness and pain over the lateral femoral epicondyle. (a) Coronal T1-weighted spin-echo MR image (550/18, 4-mm section thickness) shows poorly defined low-signal-intensity changes (straight arrows) medial to the ITT (arrowheads) and distal to the vastus lateralis muscle (curved arrow). (b) Corresponding coronal two-dimensional multiplanar gradient-recalled-echo image (600/15, 4-mm section thickness, 30° flip angle) shows high-signal-intensity alterations (arrows) that correspond to the low-signal-intensity changes in a. Arrowheads = ITT. (c) Axial T2-weighted fat-saturated fast spin-echo MR image (4,400/108, 4-mm section thickness) shows abnormal signal intensity alterations (white arrow) lateral to the lateral femoral epicondyle (black arrow). Arrowhead = ITT. (d) Axial T2-weighted fat-saturated fast spin-echo MR image (4,400/108, 4-mm section thickness) shows abnormal signal intensity alterations (solid arrows) medial to the ITT (arrowhead), adjacent to the biceps femoris muscle (open arrow) and femur.

View larger version (156K): [in this window] [in a new window]   Figure 7a. Patient 13. Images obtained in a 40-year-old jogger with anterolateral knee pain, swelling, and tenderness. (a) Coronal T2-weighted fat-saturated fast spin-echo MR image (4,400/108, 4-mm section thickness) demonstrates a high-signal-intensity large cystic fluid collection (straight arrows) medial to the ITT and extending to the tibial plateau. The lesion extends proximal to the lateral femoral epicondyle with soft-tissue edema (open arrow) adjacent to the vastus lateralis muscle (curved arrow). (b) Axial three-dimensional double-echo steady state MR image (27/9, 1.6-mm section thickness, 40° flip angle) shows a well-circumscribed fluid collection (arrow) medial to the ITT.

View larger version (147K): [in this window] [in a new window]   Figure 7b. Patient 13. Images obtained in a 40-year-old jogger with anterolateral knee pain, swelling, and tenderness. (a) Coronal T2-weighted fat-saturated fast spin-echo MR image (4,400/108, 4-mm section thickness) demonstrates a high-signal-intensity large cystic fluid collection (straight arrows) medial to the ITT and extending to the tibial plateau. The lesion extends proximal to the lateral femoral epicondyle with soft-tissue edema (open arrow) adjacent to the vastus lateralis muscle (curved arrow). (b) Axial three-dimensional double-echo steady state MR image (27/9, 1.6-mm section thickness, 40° flip angle) shows a well-circumscribed fluid collection (arrow) medial to the ITT.

View larger version (174K): [in this window] [in a new window]   Figure 8a. Patient 15. Images obtained in a 40-year-old marathon runner with persistent bilateral knee pain and tenderness. (a) Coronal T2-weighted fat-saturated fast spin-echo MR image (4,400/108, 4-mm section thickness) demonstrates small cystic fluid collections (arrow), which are 1.5 x 1.0 cm, on the right side medial to the ITT (arrowheads) adjacent to the lateral femoral epicondyle. (b) Coronal T2-weighted fat-saturated fast spin-echo MR image (4,400/108, 4-mm section thickness) shows a similar cystic lesion (arrow), which is 1.0 x 0.5 cm, on the left side. The ITT (arrowheads) shows no signal intensity alterations or thickening.

View larger version (169K): [in this window] [in a new window]   Figure 8b. Patient 15. Images obtained in a 40-year-old marathon runner with persistent bilateral knee pain and tenderness. (a) Coronal T2-weighted fat-saturated fast spin-echo MR image (4,400/108, 4-mm section thickness) demonstrates small cystic fluid collections (arrow), which are 1.5 x 1.0 cm, on the right side medial to the ITT (arrowheads) adjacent to the lateral femoral epicondyle. (b) Coronal T2-weighted fat-saturated fast spin-echo MR image (4,400/108, 4-mm section thickness) shows a similar cystic lesion (arrow), which is 1.0 x 0.5 cm, on the left side. The ITT (arrowheads) shows no signal intensity alterations or thickening.

	DISCUSSION

TOP Abstract Introduction MATERIALS AND METHODS RESULTS DISCUSSION References

These observations are in contrast to the findings of Nemeth and Sanders (15), who suggested that synovial tissue from the lateral recess insinuates itself under the ITT to become an interface between the ITT and the lateral femoral epicondyle and acts like a bursa and allows the ITT to move over the lateral femoral epicondyle with minimal shearing forces. This latter study (15), however, was performed only at full extension of the knee. Therefore, the relationships of the lateral recess to the lateral femoral epicondyle at different degrees of knee flexion were not evaluated.

While the ITBFS was previously thought to be related to either an invagination of the lateral recess of the knee joint under the ITT or inflammation of a primary bursa, the results of our cadaveric studies demonstrated additional information concerning the dynamic changes in the lateral aspect of the knee during knee flexion. The ITT, the lateral collateral ligament, the popliteus tendon, and the insertion of the tendon of the biceps femoris muscle form a complex of tissues. In extension, the ITT is normally located anterior to the femoral insertion of the popliteus tendon and the lateral collateral ligament.

In some patients, however, posterior fibers of the ITT may remain in contact with the lateral femoral epicondyle in extension. When the knee flexes, the ITT begins to move posteriorly and comes in contact with the lateral femoral epicondyle and the inserting fibers of the lateral collateral ligament below this epicondyle (Fig 3). With further flexion, however, the ITT, the lateral collateral ligament, and the popliteus tendon cross each other at one point and result in further friction of the ITT during joint motion (10).

The MR imaging characteristics in the patients with ITBFS in our study were consistent with those found by Murphy et al (12) and Nishimura et al (13). Poorly defined signal intensity alterations were observed in the fatty tissue deep to the ITT in the majority of patients, except in one patient with additional signal intensity changes superficial to the ITT. In addition, in our study the signal intensity abnormalities (high signal intensity on T2-weighted and gradient-echo sequences and low signal intensity on T1-weighted sequences) were located within a compartmentlike space demarcated laterally by the ITT and distally and medially by the meniscocapsular junction of the lateral meniscus, the lateral collateral ligament, and the lateral femoral epicondyle. Proximal to this epicondyle, the signal intensity alterations extended into the fatty tissue distal to the vastus lateralis muscle. Posterolateral signal intensity alterations were seen in an area bounded by the ITT and the biceps femoris muscle.

In common with the findings of previous studies (7,12,13), circumscribed fluid collections at MR imaging were found in a minority of patients with ITBFS in our study. In addition, these well-defined fluid collections had the same compartmentlike distribution as the poorly defined soft-tissue edema described previously. The signal intensity characteristics were similar to those observed in patients with bursitis of the pes anserinus or the tibial collateral ligament (17–19). Our results support the findings of other anatomic investigations (5,8,16–22) that suggest the well-defined fluid collections are more likely to arise from chronic inflammation beneath the ITT with formation of a secondary, or adventitious, bursa, rather than from inflammation of a primary bursa. However, further studies are necessary to verify this hypothesis.

Our observations seem to be similar to findings in patients with amputations below the knee, in whom adventitious bursae develop over the head of the fibula and the tibial tubercle because of chronic friction and pressure caused by an unsatisfactory fit or malalignment or suspension of the prosthesis (20–22). However, solely on the basis of microscopic examination as performed in patients with ITBFS treated surgically, differentiation between a true bursa and bursalike reactive tissue is sometimes difficult (2,13,15).

In addition, our results indicate a normal width of the ITT in patients with early stages of ITBFS when compared with that in a healthy control group. Our findings are in contrast to those of Ekman and co-workers (7), who noted a thickened ITT in patients with ITBFS. However, thickening of the ITT may represent a chronic stage of ITBFS rather than an acute or subacute stage of this syndrome as seen in recreational athletes or even nonathletic persons with sudden onset of clinical symptoms.

Our study has several limitations. First, due to the inability to compare MR findings with clinical data such as the duration and the severity of symptoms, no predisposing factors for the development of an adventitious bursa could be established. Second, the relationships of the ITT to the lateral femoral epicondyle at full extension and at 30° and 60° of flexion were determined in cadavers rather than in living subjects, a situation that is not entirely analogous to the examination of patients. Third, artifacts produced by anatomic sectioning or freezing may have influenced the observations, although this appeared to be a minor problem. Fourth, as only a small number of specimens derived from elderly cadavers were included in this study, it is difficult to determine the relationship of the lateral recess to the lateral femoral epicondyle during knee motion and the prevalence of a primary bursa beneath the ITT in the general population.

In summary, with MR imaging, poorly defined signal intensity abnormalities or a circumscribed fluid collection located in a compartmentlike space medial to the ITT with obliteration of the fatty layer distal to the vastus lateralis muscle may allow the diagnosis of ITBFS in patients with corresponding clinical symptoms. Our results derived from cadaveric studies demonstrate a close relationship of the ITT to the lateral femoral condyle during knee flexion. Our results also suggest that localized fluid collections in patients with the ITBFS are more likely due to inflammation of a secondary, or adventitious, bursa rather than to inflammation of synovial tissue arising from the lateral recess of the knee joint or from a primary bursa.

	Acknowledgments

 
The authors specially thank Gerd Baumer for the preparation of the positioning devices.

	Footnotes

 
Abbreviations: ITBFS = iliotibial band friction syndrome ITT = iliotibial tract

Author contributions: Guarantors of integrity of entire study, C.M., D.R.; study concepts, C.M., D.R.; study design, J.M.A., L.R.Y.; definition of intellectual content, C.M., J.M.A., D.R.; literature research, L.R.Y., C.M.; clinical studies, G.A.B., R.D.B.; experimental studies, C.M.; data acquisition, J.A.J., G.A.B., R.D.B., M.S.; data analysis, C.M., P.H., D.J.T.; statistical analysis, C.M.; manuscript preparation, D.J.T., C.M.; manuscript editing, C.M., D.R.; manuscript review, D.R.

	References

TOP Abstract Introduction MATERIALS AND METHODS RESULTS DISCUSSION References

 

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