Figure 5.

Schematic diagram illustrating factors associated with progression of knee OA and their interactions. Stronger associations are shown schematically with thicker arrows. Age: conflicting evidence is found in the relationship between age and progression of knee OA.¹⁰² Possible role of sarcopaenia, an age-associated loss of skeletal muscle mass and a major factor in the strength decline with ageing should also be considered.^{103 104} Obesity: the possible effect of obesity on progression of knee OA, in human models, has been supported by some studies.^105–108 Static (in the context of genetic traits) and dynamic knee joint alignment s: have also been associated with progression of knee OA.^{106 109} Moreover, as reported by Felson et al, the effect of body weight on progression of knee OA is affected by alignment.¹¹⁰ Genetic predisposition: is well established, and several genes have been identified as risk factors for the incidence and progression of knee OA.^111–113 Genetic predisposition might be a key difference between a patient who sustained a traumatic knee injury and fully recovers and a patient who develops early OA as a result of similar injury.¹¹⁴ A patient with predisposed malaligned knee will have a higher risk of progression compared with his ot her counterpart with neutrally aligned knee. P ain at baseline: the effect of pain on progression of knee OA is of major importance as it itself could modify or be modified by several other factors like: muscle inhibition, psychosocial factors, increased medial knee joint loading. Previous history of knee joint injury: has also been associated with increased risk of progression of knee OA.^{47 115} Previous injury could also be related to the progression of knee OA via its mediating effects on psychosocial factors (kinesiophobia¹¹⁶) and knee joint alignment. MJL, medial joint loading; OA, osteoarthritis.