Regional asymmetry, obesity and gender determines tactile acuity of the knee regions: A cross-sectional study.

BACKGROUND AND AIMS: Alterations in central somatosensory function (e.g. cortical reorganisation) occurs secondary to chronic knee pain. The reorganization can be quantified using a clinical signatory measure, the two-point discrimination threshold (TPDT). In order to differentiate normal variability of TPDT against abnormal thresholds for clinical practice, development of body region specific reference values are required and the factors that determine the TPDT have to be established.

OBJECTIVE: To establish reference values for TPDT of the knee region in healthy individuals and to determine the factors that influence the TPDT of the knee regions.

METHODS: Participants across four decades (18-59 years; n = 79) were recruited. TPDT estimates for medial and lateral knee regions were determined using a mechanical calliper. Descriptive statistics, and linear regression analyses were performed to establish reference TPDT values, and to investigate associations between demographics, anthropometric variables, and TPDT estimates respectively.

RESULTS: Participants' Mean (SD) age = 38.3 (12.2); females (n = 56); and right lower limb dominant (n = 72). Mean TPDT threshold ranges included: lateral right knee, 36.7 (14.3); medial right knee, 28.6 (9.7); lateral left knee, 37.7 (12.9); and medial left knee, 27.9 (11.4). Fifteen percent of the threshold variance (R2 = 0.148) of TPDT estimates was explained by the medial aspect (β = -8.9; p = 0.000) and male gender (β = 3.1; p = 0.057), weighted by anthropometric factors.

CONCLUSIONS: Age-stratified knee TPDT estimates have been reported to aid clinical interpretation. Regional asymmetry, gender, and obesity indices are factors that determine the TPDT of the knee. Normal TPDT asymmetry observed at medial aspect of the knee has significantly greater acuity compared to the lateral knee.