RIVCAM: a simple video-based kinematic analysis for clinical disorders of gait.

This paper describes the development of and reports on the accuracy of the Rivermead video-based clinical gait analysis method (RIVCAM), a simple and comparatively inexpensive movement recording system, which operates at 50 Hz. The system comprises five basic steps; firstly subjects are recorded using a PAL video camera with white markers affixed to the leg. Second, the video footage is digitised onto a computer. Thirdly, a program analyses each frame of footage to locate the position of white markers located on the subject's leg. Fourth, the data are calibrated (turned into real world co-ordinates) and the markers on the legs are identified (such as, heel, toe, etc.). Finally, a kinematic analysis is performed on the data, which not only produces a range of relevant spatio-temporal parameters (such as gait velocity, cadence and stride length), but also determines the joint angles at the hip, knee and ankle during the gait cycle. Overall the system has a reasonable constant and variable error; in a recorded scene measuring 2.6 x 1.6 m and divided into a 3 x 3 grid, a 400 mm bar was recorded, on average, as being 401.1 mm with a standard deviation (S.D.) of 2.97 mm. Although not without shortcomings when compared with more expensive and complicated systems, the RIVCAM system represents a valid, reliable and affordable way of collecting objective measures of gait in a busy therapy setting.