Comparing two observational systems in the assessment of knee pain

Research has demonstrated the utility of the Pain Behavior Measurement (PBM) system as a pain index. PBM involves the recording of sighing, rubbing, grimacing, guarding and bracing. A modification of this system has been proposed, focusing on the occurrence of joint flexing, rubbing, unloading the joint, guarding and rigidity, specifically for patients with knee pain. The aim of the present study was to compare the original PBM to the modified version in a sample of knee replacement patients to assess the utility of the more specialized approach. It was expected that the more discomforting physiotherapy activities (knee bending and quadriceps exercises) would result in more pain behaviours than intermediate activities (walking and standing), which, in turn, would result in more pain behaviours than reclining. The extent to which each system reflected this expected pattern was examined.

Ninety-three seniors were observed while completing a series of structured post-knee surgery physiotherapy activities (knee bending, standing, walking, reclining and a quadriceps exercise).

Analyses of self-reported levels of pain were consistent with the expected pattern of pain levels in relation to the physiotherapy activities. Specific pain behaviours within each system (eg, grimacing, rigidity) occurred in a manner consistent with the expected pattern, while other behaviours (e.g., rubbing the affected area) did not.

Although there was no clear advantage for the modified system over the PBM, an optimal approach may involve combining specific behaviours from each system.