SummaryReasons for performing study: Simple objective assessment tools are essential to monitor the clinical efficacy of therapeutic interventions used in equine orthopaedics and rehabilitation. In human medicine, goniometry is a validated tool to quantify restrictions in joint range of motion (ROM); however, the technique is not validated in horses. Objectives: To validate 2 different goniometry techniques for the measurement of passive flexion of the fetlock, carpus and hock by examining; 1) the intra-and inter-tester reliability; 2) the differences between 2 goniometry techniques and 3) differences between standing and anaesthetised horses. Methods: The study is composed of three parts: 1) the intraand inter-tester reliability was examined on 10 horses, where each horse was assessed by 5 pairs of testers measuring ROM with a universal goniometer; 2) the differences between 2 goniometry techniques were examined on 14 horses, each assessed by 2 investigators (either working in pairs with one investigator holding the limb and the other measuring the joint angle, or working individually at the same time holding and measuring); 3) on 6 horses, the differences between standing and anaesthetised horses were assessed by 2 investigators with the same techniques as described above. Nonparametric tests (Mann-Whitney, Wilcoxon sign-rank) and Intraclass Correlation Coefficient (ICC) were used for statistical analysis (P<0.05). Results: 1) The intra-tester reliability was high to excellent (ICC 0.8-1) and the inter-tester reliability low to average (ICC 0.1-0.5); 2) significant differences in joint ROM were registered in carpus and hock when measuring in pairs compared to singly and 3) significant differences in joint ROM were registered measuring anaesthetised compared to standing horses. Conclusions: As shown in human studies, goniometry is a promising tool in documenting passive flexion of fetlock, carpus and hock, if used by the same investigator. However, additional studies are needed for further validation.evj_254 676..682