Graven–Nielsen T et al. – The widespread hyperesthesia and enhanced spatial summation observed in the osteoarthritis (OA) patients imply sensitised central pain mechanisms together with the loss of Conditioning pain modulation (CPM). Normalisation of the results following joint replacement implies that these central pain processes are maintained by peripheral input.Methods
- Pain assessment was performed on 48 patients with symptomatic knee OA and 21 pain–free controls.
- Twenty patients subsequently underwent total knee replacement and were reassessed.
- Pressure pain thresholds (PPTs) were recorded using a pressure algometer (over and distant to the knee) and a double–chamber inflatable cuff mounted around the calf.
- Spatial summation was assessed by relating PPTs using the dual and single–chamber cuff.
- Conditioning pain modulation (CPM) was assessed by recording the PPT increase in response to experimental arm pain.
- PPTs at the knee and at the sites away from the knee were reduced in OA patients compared to pain–free individuals (P<0.0001).
- Cuff PPTs were decreased in OA patients (P<0.05) who exhibited a greater degree of spatial summation (P<0.05).
- Whereas an elevation of PPTs was noted in pain–free individuals in response to experimental arm pain, no such CPM was observed in the OA patients (P<0.0001).
- Following joint replacement a reduction in the widespread mechanical hyperesthesia was apparent along with normalization of spatial summation ratios and restoration of CPM.