Knee Osteoarthritis and Associated Periarticular Conditions: Iliotibial Band Friction and Baker Cyst

Abstract

Osteoarthritis (OA) is a highly prevalent disease with markedly increasing impact worldwide because of the aging of populations (Center for disease control and prevention (CDC); Murphy L.et al., 2008). It affects more than 21 milion people in the U.S. (Handout on Health: Osteoarthritis), with 36% of elderly aged 70 or older having some degree of radiographic knee OA (D’Ambrosia et al., 2005; Felson et al., 1987). It is a major public health problem, with prevalence in the knee of approximately 30% in those over 65 years old (Felson et al., 1987). The cause of knee pain in patients with OA remains unclear. Because hyaline cartilage has no innervations (Dye et al., 1998), the primary pathologic abnormality in OA (hyaline cartilage loss) could occur without pain. In MRI studies is reported an increase the prevalence of subchondral bone marrow edema, knee joint effusion, and synovial thickening in patients with symptomatic knee OA compared with patients with no symptoms (Hill et al., 2001; Felson et al., 2001). Knee with OA are biomechanically altered, and these changes may put stress on ligament and tendon insertion sites in and around the knee joint, creating pain (Hill et al., 2003). Some of the pain does not emanate from the joint itself but rather from the structures near the joint that contain pain fibers. Wide ranges of periarticular lesions occur around the knee joint, including popliteal Baker cyst (BC) (Vasilevska et.al., 2008, Janzen et al., 1994) and friction of the iliotibial band (ITBF) (Vasilevska et al., 2009). Iliotibial band friction syndrome (ITBFS) is an inflammatory overuse disorder affecting soft tissue, interposed between the iliotibial band and the lateral femoral condyle, caused by chronic friction (Muhle et al., 1999). Recently, an anatomic study disclosed a fibrous anchorage of the iliotibial band to the femur preventing rolling over the epicondyle; therefore ITBFS is mainly caused by increased pressure to the richly innervated and vascularized fat and loose connective tissue beneath the tract (Fairclough et al., 2006, 2007). Either ITBFS has been shown to cause lateral knee pain in athletes, it may be a consequence of gait changes induced by knee OA and may occur together with symptomatic knee OA (presented only 3 cases with low grade ITBF, only one with symptom) (Hill et al., 2003).