 Biomechanics of iliotibial band friction syndrome in runnersJohn W. Orchard; Peter A. Fricker; Anna T. Abud; Bruce R. Mason. The American Journal of Sports Medicine, May-June 1996 v24 n3 p375(5) Author's Abstract: COPYRIGHT 1996 American Orthopaedic Society for Sports Medicine We propose a biomechanical model to explain the pathogenesis of iliotibial band friction syndrome in distance runners. The model is based on a kinematic study of nine runners with iliotibial band friction syndrome, a cadaveric study of 11 normal knees, and a literature review. Friction (or impingement) occurs near footstrike, predominantly in the foot contact phase, between the posterior edge of the iliotibial band and the underlying lateral femoral epicondyle. The study subjects had an average knee flexion angle of 21.4[degrees] [+ or -] 4.3[degrees] at footstrike, with friction occurring at, or slightly below, the 30[degrees] of flexion traditionally described in the literature. In the cadavers we examined, there was substantial variation in the width of the iliotibial bands. This variation may effect individual predisposition to iliotibial band friction syndrome. Downhill running predisposes the runner to iliotibial band friction syndrome because the knee flexion angle at footstrike is reduced. Sprinting and faster running on level ground are less likely to cause or aggravate iliotibial band friction syndrome because, at footstrike, the knee is flexed beyond the angles at which friction occurs. Full Text: COPYRIGHT 1996 American Orthopaedic Society for Sports Medicine Iliotibial band friction syndrome (ITBFS), or iliotibial band syndrome, affects long-distance runners and other athletes. In surveys of long-distance runners, it is one of the most common injuries reported[2,8,9,16,24] It has been reported as an injury in cyclists,6 but it is not recognized as commonly affecting athletes in sprint running or multidirectional sports. The anatomy of the iliotibial band, a structure that extends from above the hip to below the knee, has been previously described.[18-20] 25 The gluteus maximus and tensor fascia late muscles attach to the iliotibial band at its proximal end. Iliotibial band friction syndrome is caused by excessive rubbing of the band over the lateral epicondyle of the femur during sporting activity, which produces pain and inflammation. The traditional explanation for the development of ITBFS includes a combination of extrinsic factors, such as training errors and downhill running, and intrinsic factors, such as a tight iliotibial band and abnormal foot biomechanics.[8] Publications on ITBFS have often mentioned associated features in these patients, but few of these features have been shown to correlate significantly with the syndrome. The purpose of this study was to establish a model of the pathogenesis of ITBFS in distance runners. MATERIALS AND METHODS The anatomy of the iliotibial band was examined with a cadaveric study. The dynamic biomechanics of runners with ITBFS were examined by video analysis of runners on a treadmill. Approval for the study was obtained from the Australian Sports Commission Ethics Committee. Cadaveric Study The anatomy of the iliotibial band at the knee was studied firsthand by examining 11 dissected cadaveric legs from separate adult bodies (9 men and 2 women). The legs were fixed in full extension as a result of the process of embalming. Measurements were taken of the width of the iliotibial band, at both its narrowest point and at the level of the lateral femoral epicondyle. We also measured the length, from the greater trochanter to its insertion at Gerdy's tubercle on the tibia. The relationship between the lateral epicondyle and the posterior edge of the band in extension was also recorded, with particular note taken of whether the iliotibial band lay over or adjacent to the lateral epicondyle. Dynamic Study Nine recreational distance runners (four men and five women), aged 27 [+ or -] 9.5 years, participated in the study. All were assessed by the principal author (JWO) and had recent (within the last 6 months) symptoms and signs typical of ITBFS. The prominent symptom in all subjects was of lateral knee pain during jagging that gradually worsened. The diagnosis was confirmed by the presence of local tenderness over the lateral epicondyle and the absence of any other signs in the knee joint proper, such as effusion or a positive McMurray's test. Exclusion criteria included a history of bilateral ITBFS, previous surgery to either lower limb, and other knee abnormalities (including patellofemoral joint pain). Informed consent was obtained from all subjects. Each subject performed two short 2-minute runs on a level treadmill at a constant pace. The pace was chosen by the subject as being most representative of his or her average speed during training (ranging between 2.78 and 3.89 m/sec). Both runs were performed with the subject wearing his or her normal running footwear, without socks. The second run was performed with a 0.5-cm heel raise inserted in the shoe of the affected side. We hypothesized that the heel raise would increase knee flexion angles in that leg. The subjects were filmed at 200 frames per second using a VICON VX 3D Motion
Analysis System (Oxford Metrics, Statistical analysis was performed using single-factor analysis of variance with a P value of <0.05 used to determine a significant result. RESULTS Cadaveric Study Measurements from the cadaveric study are presented in Table 1. Among the cadavers, there was substantial variation in both the width of the iliotibial band and its relationship to the lateral femoral epicondyle in extension. The width of the iliotibial band at the level of the lateral epicondyle ranged from 23 to 51 mm (mean, 37). The range of iliotibial band length was comparatively small. In 5 of the 11 knees, the posterior edge of the iliotibial band was overlying the lateral epicondyle in full extension. In the other six knees, the posterior edge was 3 to 9 mm anterior to the lateral epicondyle in extension. [TABULAR DATA 1 OMITTED] The five bands that were overlying the lateral epicondyle in extension were significantly wider than the other six bands (P < 0.02). Dynamic Study Kinematic results for the knee joint range of motion during the stance phase are presented in Table 2. There were no significant differences in knee angles between the affected and unaffected legs or the affected leg with and without the heel raise. [TABULAR DATA 2 OMITTED] In the study population, the position of the knee of the affected leg was closest to extension (least flexed) at foot strike. The knee joint angle for the affected leg at footstrike, averaging 21.4[degrees], was significantly less flexed than at all other measured parts of the gait cycle, including at toe-off (P < 0.002). Two of the nine subjects experienced mild knee pain during the run; the pain was typical of their ITBFS pain. Statistical analysis was repeated after removing these two subjects from the group, but there was still no significant difference between knee angles at footstrike in the affected and unaffected legs. One of the subjects who reported pain during the initial run reported that her pain was lessened during the second trial with a heel raise. This was considered a significant finding. Consequently, a third trial was performed for this subject with the addition of a larger heel raise (1.5 cm) in the shoe of the affected side. This extra trial was not included in the combined analysis. In the third trial, her pain was totally eliminated. Knee flexion angles in the affected leg footstrike were 18.5[degrees] [+ or -] 1.5[degrees], 19.5[degrees] [+ or -] 1.5[degrees] and 20.0[degrees] [+ or -] 2.8[degrees] in the three trials, respectively, for this subject. Measurements were also recorded for hip and ankle joint angles at the same phases of the gait cycle. These measurements showed no significant differences between affected and unaffected legs. The kinematic results for hip, knee, and ankle joints in the affected legs without a heel raise are presented in Table 3. [TABULAR DATA 3 OMITTED] DISCUSSION Previous publications on ITBFS have suggested that biomechanical abnormalities may predispose athletes to the syndrome, but most have not shown significant associations.[7, 15-17, 20, 24] Runners with ITBFS have been shown to have increased leg,length difference (with the syndrome developing in the shorter leg), increased forefoot varus, and increased knee Q angles compared with controls.[21] Patients with ITBFS have significantly thicker bands on MRI scans than controls without symptoms.[4] A retrospective comparison of runners with ITBFS and noninjured controls found that the injured runners had higher weekly training mileage and lower maximal normalized braking forces.[14] Combining observations in the literature with the findings in our study, some conclusions can be drawn about the pathophysiology of ITBFS, and a model can be proposed for its development. Traditionally, iliotibial band friction has been reported to occur at 30[degrees] of knee flexion.[17] This observation by itself is a simplification because knee joint angle is only one of many factors relevant to the development of friction, and it may vary depending on the other factors. We propose that iliotibial band friction occurs because of repetitive knee movement through an impingement zone (similar to the development of supraspinatus tendinitis in the shoulder). As with the shoulder, many factors contribute to impingement, and they are very complex in their interaction. Figure illustrates the proposed influence of knee joint angle and phase of gait on this impingement zone. It is likely that the impingement zone (painful arc) would increase in runners with ITBFS as inflammatory changes caused the band to swell. Iliotibial band friction in runners occurs predominantly during the early stance (foot contact) phase of gait, very soon after footstrike. This has been referred to previously as the deceleration phase.[13] Electromyographic study of joggers has shown that the gluteus maximus and tensor fascia lata, the muscles that attach to the iliotibial band, are active only during the first 35% of the stance phase (and for an even shorter period during running and sprinting).[11] In our study population, knees were consistently near 30[degrees] of flexion only just after footstrike. Some knees had returned to 30[degrees] at toe-off, but this is well after the muscles attached to the band have stopped contracting. In addition, patients with ITBFS most often feel pain just after the foot lands. The exact angle or range of knee joint angles at which iliotibial band friction may occur would vary between individuals and circumstances, although 30 of flexion is a fair approximation. We propose that for each affected individual there is a range of angles that constitute an impingement zone (similar to the painful arc seen with shoulder impingement). In our study population, the knee joint angle at footstrike in the affected legs averaged 21.4[degrees], so our proposed zone, as illustrated in Figure 1, includes angles around and slightly below 30[degrees] of flexion. The use of this new model is to explain why certain conditions of running make iliotibial band friction more or less likely. Previous authors have noted that ITBFS develops more commonly with downhill running.[7,16] During downhill running, knee flexion angle at footstrike is significantly reduced,[3] which increases the tendency to friction because the knee spends more time in the impingement zone (Fig. 1). Conversely, ITBFS is much less common in sprinters and multidirectional athletes because the knee flexion angle at footstrike increases with speed of running.[10,11,23,26] In general, the faster the speed of running the less time spent in the impingement zone. However, runners with ITBFS can avoid the pain by walking with a stiff-legged gait,[13,20] keeping the knee in full extension (0[degrees] of flexion), which is below the impingement zone. From papers reporting successful surgical management of ITBFS it is apparent that friction occurs at the posterior edge of the band[5,12,16.,17] Surgery for this condition probably has an effect similar to that of acromioplasty in the shoulder; that is, it removes some of the tissue involved in the impingement process. The present cadaveric study shows that in a normal population, there is substantial variation in the relationship of the posterior edge of the band to the lateral epicondyle. This variation may explain why certain individuals are predisposed to developing ITBFS. In knees in which the posterior edge of the iliotibial band lies anterior to the lateral epicondyle in extension (6 of 11 in the present series), it is likely that the edge meets the epicondyle near 30 of flexion. We propose that in running, friction would be much less in the nonweightbearing phase of gait just before footstrike. Although the angle of the knee is in the impingement zone, there are no ground reaction forces being absorbed and the band is moving in the opposite direction across the epicondyle. Iliotibial band friction syndrome can develop in cyclists, so full weightbearing is not essential for friction to occur, but it is likely to contribute to it. In the current dynamic study, no significant difference was seen between the knee flexion angle at footstrike on the affected side compared with the unaffected side, which was used as a control. This may be due to an inadequate sample size or possibly to gait adjustments made by the subjects after developing ITBFS. A larger prospective study comparing runners who develop ITBFS with runners who do not may show significant differences that would support the proposed model. The proposed model for the development of ITBFS has important implications for the management of the injury. A period of total rest has been previously advised as treatment[.2,22] Once the initial inflammation has subsided, patients can be encouraged to train freely at activities that involve faster running than their usual training pace, including multidirectional sports such as tennis and basketball. These activities are unlikely to cause or aggravate ITBFS, unless the iliotibial band is already inflammed, because the knee would not be moving through the impingement zone. Slower jogging should only be attempted after successful return to faster activities has been made, which is opposite to the management of most injuries. Downhill running is to be particularly discouraged, and runners should be advised to train on flat terrain to prevent a recurrence of the condition. Adjustments to running gait that cause the knee to be in a more flexed position at footstrike may prevent ITBFS from occurring. In this study, it was proposed that addition of a heel raise into the shoe on the affected side may increase the knee flexion angle at footstrike. However, we found that the effects of the heel raise were inconsistent. In one subject who experienced knee pain during testing, the addition of a heel raise relieved the pain by the proposed mechanism, increasing the knee flexion angle at footstrike. However, in other subjects the heel raise had the opposite effect on the knee flexion angle at footstrike. Further study is required to assess the effects of footwear on knee flexion angle at footstrike and therefore subsequent development of ITBFS. This paper only considers the mechanics of the ITBFS in the sagittal plane. It is likely that mechanics of band tightness in the coronal plane and rotation of the tibia in the transverse plane are relevant to the condition.] Another consideration is the space between the iliotibial band and the lateral epicondyle, which has been described as a bursa[4,l9] or degenerate fibrous tissue.[l2,17] Friction between the iliotibial band and the tissue of the space may be relatively painless, with a sharp pain suddenly developing if the band rubs through the space against the underlying periosteum of the lateral epicondyle. CONCLUSIONS The width of the iliotibial band varies substantially among the normal population. In ITBFS in runners, the posterior edge of the band impinges against the lateral epicondyle of the femur just after footstrike in the gait cycle. The friction occurs at, or slightly below, 30[degrees] of knee flexion. Downhill running and slower speeds of running, which cause the knee to be less flexed at footstrike, predispose the athlete to the development of ITBFS. ACKNOWLEDGMENTS The authors thank the Anatomy Departments of the [Figure 1 ILLUSTRATION OMITTED] REFERENCES [1.] Anderson GS: Iliotibial band friction syndrome. Aust J Sci Med Sport 23:
81-83, 1991 [2.] Aronen JG, Chronister R, Regan K, et al: Practical,
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59-69, 1993 [3.] [5.] Firer P: Results of surgical management for the iliotibial band friction syndrome. Clin J Sport Med 2: 247-250, 1992 [6.] Holmes JC, Pruitt AL, [7.] Lindenberg G, Pinshaw R, Noakes TD: Iliotibial band friction syndrome in runners. Physician Sportsmed 12(5): 118-130, 1984 [8.] Lineger JM, Christensen CP: Is iliotibial band syndrome often overlooked? Physician Sportsmed 20(2): 98-108, 1992 [9.] Macintyre JG, Taunton JE, Clement DB, et al: Running injuries: A clinical study of 4,173 cases. Clin J Sport Med 1: 81-87, 1991 [10.] Mann RA, Hagy J: Biomechanics of walking, running, and sprinting. Am J Sports Med 8: 345-350, 1980 [11.] Mann RA, Moran GT, Dougherty SE: Comparative electromyography of the lower extremity in jogging, running, and sprinting. Am J Sports Med 14: 501-510, 1986 [12.] Martens M, Libbrecht P, Burssens A: Surgical treatment of the iliotibial band friction syndrome. Am J Sports Med 17: 651-654, 1989 [13.] McNicol K, Taunton JE, Clement DB: Iliotibial tract friction syndrome in athletes. Can J Appl Sport Sci: 76-80, 1981 [14.] Messier SP, Edwards DG, Martin DF, et al: Etiology of iliotibial band friction syndrome in distance runners. Med Sci Sports Exerc 27: 951-960, 1995 [15.] Messier SP, Pittala KA: Etiologic factors associated with selected running injuries. Med Sci Sports Exerc 20: 501-505, 1988 [16.] Noble CA: Iliotibial band friction syndrome in runners. Am J Sports Med 8: 232-234, 1980 [17.] Noble CA: The treatment of iliotibial band friction syndrome. Br J Sports Med 13: 51-54, 1979 [18.] Ober FR: The role of the iliotibial band and fascia late as a factor in the causation of low-back disabilities and sciatica. J Bone Joint Surg 18: 105-110, 1936 [19.] Orava S: Iliotibial tract friction syndrome in athletes--an uncommon exertion syndrome on the lateral side of the knee. Br J Sports Med 12: 69-73, 1978 [20.] Renne JW: The iliotibial band friction syndrome. J Bone Joint Surg 57A: 1110-1111, 1975 [21.] Schwellnus MP: Lower limb biomechanics in runners with the iliotibial band friction syndrome. Med Sci Sports Exerc 25: S68, 1993 [22.] Schwellnus MP, Theunissen L, Noakes T, et al: Anti-inflammatory and
combined anti-inflammatory/analgesic medication in the early management of
iliotibial band friction syndrome. [23.] Siler WL, Martin PE: Changes in running pattern during a treadmill run to volitional exhaustion: Fast versus slower runners. Int J Sport Biomech 7: 12-28, 1991 [24.] Sutker AN, Jackson DW, Pagliano JW: Iliotibial band syndrome in distance runners. Physician Sportsmed 9(10): 69-73, 1981 [25.] Terry GC, Hughston JC, [26.] Williams KR, Snow R, Agruss C: Changes in distance running kinematics with fatigue. Int J Sport Biomech 7: 138-162, 1991 (*) A preliminary account of this work was presented at the Australian
Conference of Science and Medicine in Sport in No author or related institution has received any financial benefit from research in this study. See "Acknowledgments" for funding information.
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