Site Matters in Arthritis
Written by Editor   
Thursday, June 05, 2014 08:19 AM

Osteoarthritis (OA) of the knee and hand differ in the main processes underlying disease development, with mechanical factors playing a larger role when the knee is affected, and systemic contributors being prominent for the hand.  

When OA was present in the knee, significant associations after adjustment for metabolic factors were seen for weight and fat-free mass factors considered surrogates for mechanical stress.  In contrast, after adjustment for weight, hand OA was associated with metabolic syndrome which was considered a surrogate for systemic factors.  

Obesity has been linked with OA in both weight-bearing joints, such as the knee, and nonweight-bearing joints, such as those of the hands. It is also associated with mechanical stresses that can damage joints, and systemic factors such as hyperglycemia and atherosclerosis have been linked with the pathogenesis of OA, but the possibility that the relative contributions of these factors may differ between weight-bearing joints and nonweight-bearing joints has been unclear.

The researchers noted that they had expected knee/hand OA to be associated with systemic factors as was hand-only OA, but this was not the case.

"This observation suggests that co-occurrence of knee and hand OA may not be based on a common underlying pathogenic mechanism, but may represent the presence of two different types of OA," they wrote.

The finding that hand OA was associated with metabolic syndrome was novel and may relate to the presence of systemic inflammation, the authors noted.

"Adipose tissue is known as a source of pro-inflammatory and anti-inflammatory cytokines, which have been related to the metabolic syndrome and have been suggested to affect joint tissues," they explained.