Knee osteoarthritis (KOA) is often studied in pharmaceutical trials of drugs with focus

Knee osteoarthritis (KOA) is often studied in pharmaceutical trials of drugs with focus on the analgesic and/ or anti-inflammatory properties. However, there is accumulating evidence that central and peripheral changes are just as prominent as the nociceptive and neurogenic processes. In this study, 37 subjects with KOA were compared with 35 controls for psychophysical characteristics; thermal, mechanical, and functional wind-up; thermal and mechanical after sensations; and pressure algometry. 

The majority of subjects had abnormalities to pinprick (41% were hyperalgesic and 27% were hypoesthetic). Compared to controls, the more painful knee was hypoesthetic to cold detection, had lower pressure-pain thresholds and twice the pain ratings of controls after stair climb. Subjects had greater but not significant differences thermal wind-up, thermal and mechanical aftersensations. 

Both peripheral (PS) and central sensitisation (CS) have been implicated to be prominent in OA. There is accumulating evidence to support complex heterogeneous mechanisms. Whether these results actually distinguish between PS and CS needs to be carefully studied with validated technologies that can distinguish between peripheral and central processes. > From: Harden et al., J Pain 14 (2013) 281-289. All rights reserved to the American Pain Society.