Further exploring the relationship between pressure pain thresholds and function in knee osteoarthritis.

BACKGROUND

Studies in Knee Osteoarthritis (KOA) have shown lowered Pressure Pain Threshold (PPT) values compared to healthy controls potentially signifying mechanical hypersensitivity, although the relevance of these findings to knee function remains unclear.

OBJECTIVE

This study further explores the relationship between PPT measures and knee function (self-reported, physical) in individuals undergoing total knee arthroplasty for advanced KOA.

DESIGN

Cross-sectional observational study.

METHODS

PPT's were recorded both local to the affected knee and at a remote site (deltoid) in 79 individuals with advanced KOA. Participants also completed self-report (Knee Society Score - functional sub-score) and physical (6-min walk test distance)) measures of knee function, as well as measures of pain-related psychological distress. Hierarchical linear regression models evaluated the relationship between the measures of function (self-report and physical measures modelled separately), PPT measures (local and remote), while accounting for demographic and psychological distress measures.

RESULTS

Higher knee PPT scores were independently associated with higher self-reported knee function (β 0.33, p < 0.02) and higher 6-min walk test distance (β 0.41, p < 0.01), although pain self-efficacy (β 0.33, p < 0.01) was also a significant variable in both models. Nearly identical findings were evident for PPT's measured at the deltoid. Overall PPT's could only explain a modest portion of variance (adjusted R = 0.15 to 0.17) in the functional measures.

CONCLUSIONS

PPT measures may be limited in their capacity to distinguish the impact of peripheral and central pain mechanisms on knee function in individuals undergoing total knee arthroplasty for advanced KOA.