Reliability of DIERS pedogait system for evaluating spatiotemporal gait parameters in knee osteoarthritis and its association with Achilles tendon stiffness asymmetry

Xingxing Shen¹Jiahao Chen¹Jiahao Zhang¹Jiaqing Tian¹Sirun Cheng¹Jichuan Cao¹Congcong Li^2*Xuemeng Xu^3,4*

• ¹Fifth Clinical School of Medicine, Guangzhou University of Chinese Medicine, Guangzhou, China
• ²The First Affiliated Hospital of Zhejiang Chinese Medical University, Hangzhou, China
• ³Guangdong Second Traditional Chinese Medicine Hospital, Guangzhou, China
• ⁴Guangdong Provincial Key Laboratory of Research and Development in Traditional Chinese Medicine, Guangzhou, China

Objective: To assess the inter-rater and test-retest reliability of the DIERS pedogait system for measuring gait parameters in patients with knee osteoarthritis (KOA), and to explore inter-limb differences in Achilles tendon (AT) properties, as well as the associations between the AT stiffness asymmetry index (AsyStiffness (AT)) and gait abnormalities, visual analog scale (VAS) scores, and Kellgren-Lawrence (K/L) grades. Methods: A total of 36 patients with KOA were enrolled. Two independent assessors used the DIERS pedogait system to measure gait parameters, with retesting by the first assessor 1 week later. Inter-rater and test-retest reliability were quantified using intraclass correlation coefficients (ICC), while absolute reliability was assessed using standard error of measurement (SEM), minimum detectable change (MDC), and Bland-Altman analysis. Bilateral AT muscle tone and stiffness were evaluated using the MyotonPRO. Spearman correlation and multiple linear regression analyses were performed to explore the associations of AsyStiffness(AT) with both clinical variables and gait parameters. Result: The DIERS pedogait system exhibited excellent inter-rater (ICC: 0.900-0.987) and test-retest reliability (ICC: 0.927-0.988). Inter-rater SEM and MDC ranged from 0.07 to 44.26 and 0.20 to 122.68, respectively, while test-retest SEM and MDC ranged from 0.05 to 39.59 and 0.13 to 109.74. Bland-Altman analysis revealed no significant systematic bias. In addition, AT muscle tone and stiffness were significantly higher in the relatively severe leg (RSL) compared with the moderate leg (RML) (P < 0.05). AsyStiffness (AT) was positively correlated with stance phase symmetry index (ρ= 0.514, P = 0.001), stride time (ρ= 0.381, P = 0.022), VAS score (ρ= 0.373, P = 0.025), and K/L grade (ρ= 0.542, P = 0.001), and negatively correlated with gait speed (ρ = −0.374, P = 0.025). Multiple linear regression identified stance phase symmetry index (β′ = 0.298, P = 0.043) , K/L grade 2 (β′ = 0.533, P = 0.017) and K/L grade 3 ( β ′ = 0.778, P = 0.002) as independent factors associated with AsyStiffness (AT). Conclusion: The DIERS pedogait system is a reliable and objective tool for assessing gait in KOA patients. AT stiffness asymmetry is associated with gait abnormalities, pain, and KOA severity.