### RESULTS: Linear Kinematics

Joint Position.The overall linear displacement of the ankle joint was similar in both the Hope and Standard crutch movements. The vertical excursion of the Hope crutches was 0.20 meters compared to 0.17 meters obtained using the Standard crutches. Regarding the horizontal component, both remain relatively constant and then begin to slope upwards at 58% (Hope) and 55% (Standard) of the gait movement. The maximum horizontal displacements were similar as well; 1.39 meters with the Hope crutches and 1.42 meters with the Standard crutches.
 Figure 8. Position of the ankle joint during Hope-crutch gait (left) and Standard-crutch gait (right). Positions indicate distance of the ankle from the reference marker. Positive values correspond to movement forward in the horizontal direction and upward in the vertical direction. The long dashed line represents the horizontal position, the short dashed line represents the vertical position, and the solid line represents the combined position.

Joint velocity. The linear velocity of the ankle joint differed slightly between the movements. With both crutches, maximum horizontal velocity was reached at 80% of the crutch-gait. From the data, it was observed that the vertical component of the velocity had minimal impact on the combined velocity compared to the horizontal component. Maximum horizontal velocity for the Hope crutches was 3.68 m/s and the maximum horizontal velocity for the Standard crutches was 3.41 m/s.

 Figure 9. Velocity of the ankle joint marker during Hope-crutch gait (left) and Standard-crutch gait (right). Positive values indicate forward velocity in the horizontal direction and upward velocity in the vertical direction. The long dashed line represents the horizontal movement, the short dashed line represents the vertical movement, and the solid line represents the combined movement.

Center of mass. In the Hope-crutch gait the center of mass was located directly posterior to the trunk. However, in the Standard-crutch gait the center of mass was located anterior to the trunk. Further, the center of mass for the Hope crutches is located more distally to the body than the center of mass for the Standard crutches.
 Figure 10. Location of the center of mass (CM) for the Hope-crutch gait (left) and the Standard-crutch gait (right). The forearm, upper arm, trunk, leg, shank and foot are the segments displayed in the stick figures.