Reliability and standard error of measurement of pressure pain thresholds at articular landmarks

Pressure pain threshold (PPT) testing is a widely used quantitative sensory testing method to assess mechanical pain sensitivity. While reference values for PPT at articular-/joint-related and osseous landmarks are available, data on measurement reliability remain limited. This study aimed to determine the intra- and inter-rater reliability of PPT measurements and to report the standard error of measurement (SEM) for joint PPT.

Healthy participants aged 18-40 years were included in a two-part study. In Part A (N = 40), intra-rater reliability was assessed through three repeated PPT measurements by the same examiner. In Part B (N = 40), inter-rater reliability was evaluated with two different examiners. PPT was measured at joints (elbow, knee, ankle) and reference landmarks (sternum, forehead) using a digital algometer. ICCs (2,k model) and SEM were calculated for each landmark.

Intra-rater reliability was excellent at all landmarks (ICCs ≥ 0.926) except the elbow with a good reliability (ICC = 0.848). Inter-rater reliability was excellent at the sternum (ICC = 0.950) and good at the ankle, knee, elbow, and forehead (ICCs ≥ 0.813). SEM values varied across landmarks, with lowest values observed at reference landmarks sites (e.g., sternum and forehead). ICCs are similar between sexes.

PPT measurements at articular (joints) and bony reference landmarks show good to excellent reliability. These findings support the use of joint PPT in standardized pain sensitivity assessments and provide a basis for clinical and research applications. However, findings are limited to pain-free participants and should be replicated in broader populations.