Cognition, perception strongly influence disability in knee OA

Among people with knee osteoarthritis, knee-related disability appears to be affected by cognitive factors and a disturbed body perception, a recent Japan study has found.

In 303 knee OA patients (mean age, 69.1±9.9 years; 237 women), latent profile analysis identified four distinct clusters based on patient demographic, clinical, and cognitive factors. Class 1 (n=87; 28.7 percent) included those with mild radiographic OA and moderate degrees of perceptual and cognitive dysfunction; in class 2 (n=57; 18.8 percent), radiographic OA was advanced, while cognitive and perceptual dysfunction remained moderate.

Meanwhile, class 3 (n=104; 34.3 percent) showed a mix of radiographic findings, along with minimal perceptual and cognitive dysfunction. Class 4 (n=55; 18.1 percent) participants also had a variety of radiographic findings but showed the most severe cognitive and perceptual profile.  

The researchers measured the severity of structural changes using the 5-point K/L scale, while the Japanese version of the Pain Catastrophizing Scale was used to assess pain-related catastrophizing. Self-reported body perception of the knee was evaluated using the Fremantle Knee Awareness Questionnaire. The Oxford Knee Score (OKS) was used to quantify disability.

Comparisons between groups revealed discrepancies between structural pathology and clinical status. Classes 1 and 3, for example, generally had comparable levels of knee OA severity, but the latter showed significantly lower OKS scores.

“This might be explained by the greater cognitive and perceptual dysfunction seen in cluster 1, particularly as pain intensity is not significantly different between these two groups,” the researchers explained.

On the other hand, while classes 1 and 2 differed largely in terms of radiographic knee OA severity, they showed comparable levels of pain intensity and disability.

“In both these comparisons disability maps to cognitive and perceptual function, not radiographic status. Radiographic changes on imaging might be the defining feature of knee OA, but these data suggest the functional impact on the individual is more related to their thoughts about the meaning of pain, the confidence they have in their knee, and how the knee feels to them,” the researchers said.