Associations between mechanical scar properties and pressure pain sensitivity after hip and knee arthroplasty: a preliminary cross-sectional study

Background Scar assessment after total hip (THA) or knee arthroplasty (TKA) is clinically relevant because alterations in adherence, stiffness, and pain sensitivity may influence movement and functional recovery. However, objective evidence on relationships among mechanical and sensory scar properties after orthopedic surgery remains limited. This exploratory study aimed to characterize scar mechanical and sensory properties after hip and knee arthroplasty and investigate associations among adherence, tissue stiffness, and pain sensitivity. Methods This preliminary cross-sectional study included 21 individuals (6 knee and 15 hip arthroplasties) who had undergone primary unilateral arthroplasty at least one year earlier. Scar assessment included the Patient and Observer Scar Assessment Scale (POSAS), adheremeter (adherence), indentometry (tissue stiffness), and pressure algometry (pain threshold). Correlation analyses were performed using Pearson or Spearman coefficients according to data distribution, adopting a 5% significance level. Results Mean values were: POSAS Observer 17.52 ± 3.86, POSAS Patient 15.90 ± 9.49, adherence 0.51 ± 0.20, tissue stiffness 2.60 ± 1.42 N/mm, and pain threshold 21.54 ± 13.36 N. No correlations were observed among adherence, tissue stiffness, and pain threshold. A moderate negative correlation was found between tissue stiffness and POSAS Observer scores (r = −0.590, p=0.004). Conclusion Scar adherence, stiffness, and pain sensitivity were not significantly associated in this preliminary sample. These findings should be interpreted cautiously given the small sample and exploratory design, highlighting the need for larger studies to clarify the clinical implications of objective scar assessment in musculoskeletal rehabilitation.