Clinical History: A 30-year-old female distance runner presents with lateral knee pain. (1a) T1-weighted and (1b) STIR coronal images are provided. What are the findings? What is your diagnosis?
1a
1b
Figure 1:
(1a) T1-weighted and (1b) STIR coronal images
Findings
2a
2b
Figure 2:
(2a) The T1-weighted coronal image demonstrates intermediate signal intensity (arrows) replacing normal fat signal intensity deep to the iliotibial band (arrowhead). (2b) The STIR coronal image demonstrates ill defined increased signal intensity (arrows) deep to the iliotibial band (arrowhead). Subtle increased signal intensity (short arrows) is also present superficial to the iliotibial band.
Diagnosis
Iliotibial band friction syndrome.
Discussion
Iliotibial band friction syndrome (ITBFS) is a frequently encountered overuse injury caused by repetitive friction between the iliotibial band and the lateral femoral epicondyle during active flexion and extension at the knee.
The iliotibial band (ITB) is a thickened fascia that forms from the fascial investments of the tensor fasciae latae, gluteus maximus, and the gluteus medius muscles. Proximal to the knee, the ITB inserts on the supracondylar tubercle of the lateral femoral condyle and blends with the intermuscular septum. Distally its main attachment is the Gerdy tubercle (3a).1 The ITB is located anterior to or adjacent to the lateral femoral epicondyle with the knee extended (4a). The width of the ITB varies among individuals and may be a contributing factor to the development of ITBFS in athletes.2
3a
Figure 3:
(3a) In this 3-D graphic representation of the lateral knee in extension the iliotibial band (ITB) is seen to slightly overlie the lateral epicondyle (asterisk), just anterior to the fibular collateral ligament (FCL) proximal insertion. The popliteus tendon (PT) and distal biceps femoris tendon (BF) are indicated.
4a
Figure 4:
(4a) An axial proton-density weighted image demonstrates the ITB (arrowhead) located anterior to the lateral femoral epicondyle (asterisk). The arrow indicates the posterior extent of the lateral synovial recess. Note its location anterior to the lateral epicondyle. The signal changes of ITBFS commonly extend over or posterior to the lateral femoral epicondyle.
With repetitive flexion and extension while weight bearing, the taut ITB repeatedly passes over and compresses the lateral femoral epicondyle and the proximal inserting fibers of the fibular collateral ligament. With further flexion the ITB crosses the fibular collateral ligament and the popliteus tendon, which further increases compression (5a). This repetitive friction causes irritation and creates an inflammatory response in the soft tissues between the ITB and the lateral femoral condyle (6a). The propensity to develop ITBFS is further increased by underlying biomechanical abnormalities including genu varum, excessive pronation of the foot, or an abnormally prominent lateral femoral epicondyle.
5a
Figure 5:
(5a) Contact between the Iliotibial band (ITB) and the lateral femoral epicondyle (asterisk) begins at just under 30 degrees of flexion at the knee. The ITB also contacts the proximal fibers of the fibular collateral ligament (FCL) and crosses the popliteus tendon (PT) with further flexion. The distal biceps femoris tendon (BF) is indicated.
6a
Figure 6:
(6a) The red-hatched area in this T1-weighted coronal image demonstrates the space between the Iliotibial band (arrowhead) and lateral epicondyle (asterisk) that is affected by Iliotibial band friction syndrome.
ITBFS is most commonly seen in runners or cyclists, often following a significant increase in training. ITBFS is increasingly recognized in other sports including soccer, weightlifting, and skiing. The patient presents with tenderness over the lateral femoral epicondyle and a reproducible pain examination with flexion and extension. Although typically a straightforward diagnosis based on physical exam and clinical history, the clinical presentation of ITBFS may be confused with lateral meniscal tear, popliteus strain, fibular collateral ligament sprain, or lateral hamstring strain.
The characteristic MRI appearance of ITBFS is that of ill-defined increased T2 signal intensity within the fatty soft tissues between the ITB and the lateral femoral epicondyle (2a, 2b, 6a).3 Cystic areas representing primary or secondary (adventitious) bursae may be identified (7a).4,5 In chronic ITBFS, thickening of the ITB and increased T2 signal intensity superficial to the ITB are occasionally seen. Care must be taken to identify the lateral synovial recess as a separate structure and not confuse its joint fluid with soft tissue inflammatory changes. This is made easier by understanding that the anterior lateral synovial recess is located anterior to the lateral femoral epicondyle (4a), in contrast to the inflammatory changes of ITBFS, which frequently overlie and extend posterior to the epicondyle (8a).5
7a
Figure 7:
(7a) A fat suppressed proton-density weighted coronal image demonstrates bursae (arrows) deep to the ITB (arrowhead).
8a
Figure 8:
(8a) A fat suppressed proton-density weighted axial image demonstrates increased signal (arrows) located deep to the ITB (arrowhead). The abnormal signal extends superficial and posterior to the level of the lateral femoral epicondyle (asterisk).
Treatment programs consist of stretching of the ITB, identification and correction of any underlying structural abnormalities, rest, and anti-inflammatory medication. If symptoms fail to respond to these conservative measures, further restriction of activity and local corticosteroid injections may be necessary. Surgical release of the posterior ITB fibers is rarely indicated.
Conclusion
Iliotibial band friction syndrome is a common condition among runners and cyclists, typically encountered following a significant increase in training. The clinical presentation of ITBFS may be confused with other causes of lateral knee pain. In such cases the MRI findings of ITBFS are characteristic, enabling appropriate treatment measures.
References
1 Grana WA, Larson RL. Functional and surgical anatomy. In: Larson RL, Grana WA, eds. The knee: form, function, pathology, and treatment. Philadelphia, PA: Saunders, 1993; 11-50.
2 Orchard JW, Fricker PA, Abud AT, Mason BR. Biomechanics of iliotibial band friction syndrome in runners. The American Journal of Sports Medicine 1996: 24 (3): 375-379.
3 Murphy BJ, et al. Iliotibial Band Friction Syndrome: MR imaging findings. Radiology 1992: 185: 569-571.
4 Ekman EF, Pope T, Martin DF, Curl WW. Magnetic resonance imaging of iliotibial band syndrome. The American Journal of Sports Medicine 1994: 22 (6): 851-854.
5 Muhle C, et al. Iliotibial Band Friction Syndrome: MR Imaging Findings in 16 Patients and MR Arthrographic Study of Six Cadaveric Knees. Radiology 1999; 212: 103-110.