Curr Rev Musculoskelet Med (2010) 3:18–22 Based on these anatomical considerations, they believe that anterior–posterior glide of the ITB is impossible, and a friction syndrome cannot truly exist in the region. Instead, they propose that an illusion of anterior–posterior move- ment of the ITB results from repetitive cycles of tightening; with each cycle of tightening the lateral fascia exerts a repetitive compression effect on connective tissues lying deep to the ITB. The study of Hariri and others also calls into question whether inﬂammation of the ITB is actually involved in ITBFS [11]. In their case series, the symptoms of ITBFS were alleviated by surgical excision of what they described as a bursa in the sub-ITB space. Costa and colleagues also reported on a case in which a large cyst, arising from the joint capsule, was discovered in a 28-year old runner with lateral knee pain [12]. Nemeth and Sanders may have been describing the same tissue in their anatomical review [13], but they referred to it as a lateral extension of the knee synovial capsule. On the other hand, Isusi and others did not identify a bursa in the area, but did report MRI ﬁndings of signal changes from the soft tissues immediately below the ITB, and osseous edema and subchondral osseous erosion of the lateral condyle, without evidence of inﬂammation or thickening of the band itself [14]. Further supporting this view is the study of Muhle and others [15], whose MRI studies of both cadavers and ITBFS patients showed poorly deﬁned signal intensity abnormalities in a compartment-like space bounded laterally by the ITB, but did not identify a bursa, cyst, or lateral recess in this area, or pathological changes in the band itself. Nemeth and Sanders reported similar ﬁndings [13]. It may be that different subtypes of iliotibial band friction syndrome exist, one that involves irritation of a cyst, bursa, or lateral synovial recess, and a second type arising from compression by the iliotibial band of the connective tissues that underlie the portion of the band between the lateral epicondyle and the knee joint line. There is less evidence that a pathological change takes place in the iliotibial band itself. Whether actual anterior–posterior friction-producing motion of the ITB takes place or not is also controversial. What are the biomechanical factors that contribute? Weak hip abductors? It would be logical to correlate the presence of weak hip abductors with iliotibial band friction syndrome, since weak abductors might lead to increased hip adduction during the stance phase of gait with a consequent increase strain of the iliotibial band and a greater tendency for it to compress the tissues underneath. 19 MacMahon and colleagues, Noehren et al., and Fredericson et al. all reported that ITBFS sufferers had abductor weakness or increased hip adduction during the stance phase of gait, a ﬁnding which could be interpreted as being due to abductor weakness [4, 16, 17]. On the other hand, Grau et al., using a dynamometer that was mechanically stabilized instead of hand-held, did not ﬁnd hip abductor weakness in their study of 10 runners with ITBFS as compared to healthy matched controls [18]. Thus, we may have more to learn about the relationship of iliotibial band friction syndrome to hip abductor weak- ness or to the related issues of the timing and magnitude of hip abductor activation during the gait cycle and the amount of hip adduction that occurs during the stance phase of gait. Tight iliotibial band? It is also logical to link tightness of the ITB with iliotibial band friction syndrome, since presumably a tighter band would lead to greater compression of the underlying tissues with each gait cycle. The Ober test is most commonly used to assess tightness of the iliotibial band. As described by Gajdoski et al. [19], the Ober test is performed with the examiner standing behind the side-lying patient. The examiner stabilizes the pelvis with one hand, ﬂexes the uppermost thigh, and then moves it into maximal abduction. He or she then maintains the abduction while moving the thigh into extension. The examiner then lowers the limb into adduction until it stops, or until the pelvis starts to tilt. The angle of hip joint adduction (or abduction, if the thigh cannot adduct even to neutral) is considered to be a measurement of ITB length or distensibility. Gajdoski’s article also describes variations of the Ober test that call for the knee of the side being tested to be either ﬂexed or extended. However, no study to date has actually correlated the ﬁndings of the Ober test (or any other test for ITB dis- tensibility) with iliotibial band friction syndrome. More- over, Devan and others did not ﬁnd a correlation between a positive Ober test and the occurrence of ITBFS in female college athletes [8]. On the other hand, Fredericson [20] believes that most athletes with ITBFS exhibit a tight iliotibial band, though the Ober test and other clinical examination methods, as they are used in common clinical practice, may not be sensitive enough to detect it. In 2007, Hamill, Miller, Noehren, and David published ﬁndings that showed that runners with ITBFS had a ‘‘looser’’ iliotibial band, exhibiting increased strain (it elongated more when subject to an external load) and, to a statistically signiﬁcant degree, an increased strain rate (it elongated more rapidly) during running [21].