Non-Weightbearing in Hinged-Knee Braces Locked in High Degrees of Flexion Shows High Hamstring Muscle Activation in Healthy Volunteers.

PURPOSE: To determine the effect of various postoperative ambulation and bracing protocols on hamstring muscle group activation in healthy volunteers. METHODS: Hamstring muscle group activation was assessed via Myontec Mbody 3 Shorts. Volunteers ambulated 10 yards in conditions including walking unassisted, flat-foot weightbearing (FFWB), FFWB with a Newport abduction hip brace restricting motion past 90° of flexion, FFWB with an unlocked hinged-knee brace, and non-weightbearing (NWB) in hinged-knee braces locked in 90°, 60°, and 30° of flexion. Data was standardized with the unassisted walking condition as the reference. Each condition was tested on both extremities. Primary outcomes were normalized cumulative hamstring activation and normalized peak hamstring activation on the protected extremity. Analysis of variance and post hoc Tukey tests were performed. RESULTS: Fifteen healthy volunteers with no history of hip or knee surgery were recruited over a 1-year period from June 2023 to June 2024. Analysis of variance testing showed statistically significant differences in both cumulative ipsilateral hamstring muscle activation (P = .002) and peak ipsilateral hamstring muscle activation (P = .004). Post hoc Tukey testing showed significant differences in cumulative ipsilateral hamstring muscle activation between NWB hinged-knee braces locked at 90° compared with 30° (3.38 (standard deviation [SD]: 4.03) vs 1.49 (SD: 2.13), P = .01) and NWB hinged-knee braces locked at 90° compared with FFWB with unlocked hinged-knee braces (3.38 (SD: 4.03) vs 1.54 (SD: 1.15), P = .01). For normalized peak muscle activation, significant differences were noted from NWB hinged-knee braces locked at 60° compared with FFWB (1.12 (SD: 1.21) vs 0.58 (SD: 0.50), P = .02), and NWB hinged-knee braces locked at 60° compared with FFWB with hinged-knee braces unlocked (1.12 (SD: 1.21) vs 0.61 (SD: 0.57), P = .03). CONCLUSIONS: Healthy volunteers showed lower levels of cumulative hamstring muscle activation during FFWB with an unlocked hinged-knee brace compared with NWB with hinged-knee braces locked at 90° and NWB with hinged-knee braces locked at 30° compared with NWB with hinged-knee braces locked at 90°. Lower levels of peak hamstring muscle activation were noted during FFWB compared with NWB hinged-knee braces locked at 60° and FFWB with an unlocked hinged-knee brace compared with NWB hinged-knee braces locked at 60°. LEVEL OF EVIDENCE: Level IV, retrospective case series.