Intrarater and Interrater Agreement of the Intrinsic Foot Muscle Test

Context: The intrinsic foot muscle test (IFMT) is purported to identify intrinsic foot muscle (IFM) weakness during clinical examination. However, before this test can be used in clinical practice the clinometric properties must be determined. In addition, it is unclear if the IFMT provides information regarding the integrity of the foot arch beyond static foot posture assessments such as the navicular drop test (NDT). Objective: To determine the reliability of the IFMT as well as its correlation with the NDT. Setting: Laboratory. Patients or other Participants: Two novice ATs served as the raters. The NDT was assessed by a third investigator during the first session. Twenty-five participants (16 females, 9 males; age: 22.4 ± 1.7 years; height: 170.8 ± 10.2 cm; mass: 73.5 ± 12.8 kg) completed two data collection sessions separated by one week. Interventions: During each session the IFMT was assessed bilaterally in a counterbalanced order by the raters. Each test was rated simultaneously by both raters during each trial and the raters were blinded to each other’s results during and between test sessions. Main Outcome Measures: The independent variable was time (session one and session two) and the dependent variables included rating on the IFMT and navicular drop height. Results: Intrarater agreement was poor to fair (κ =.03–.41) and interrater agreement was fair to moderate (κ =.25–.60). Post hoc Wilcoxon rank tests demonstrated a significant number of participants improved between sessions for both raters. A weak correlation was observed between the NDT and IFMT for both right (r = –.14 to.04, p >.49) and left (r = –.19 to.07, p >.37) feet. Conclusion: The IFMT demonstrated poor to fair intrarater and fair to moderate interrater agreement, suggesting future research is needed to modify this method of measuring IFM function. The improvement between sessions indicates a potential familiarization period within the test. The weak correlation between the IFMT and NDT indicates these tests evaluate different aspects of foot function.