Studies of dynamic ligamentous instability of the knee by electrogoniometric means

Ligamentous injuries to a knee joint increase the risk of post-traumatic degenerative changes. Successful early diagnosis and treatment of such injuries remains a challenging and controversial task. There are a variety of clinical tests available and some of these are difficult to perform and interpret. These clinical tests are really static in nature and may not reveal the presence of what is essentially a dynamic event. A complete assessment would need to be "dynamic" and by its application during ambulation, incorporate the effects of ground-foot forces, joint motions and muscle activities. At the Ontario Crippled Children's Centre (OCCC) a triaxial electrogoniometer system (extensively modified CARS-UBC) has been used, together with complementary gait laboratory instrumentation, in order to study the knees of 16 male subjects. Ten subjects had knees without evidence of injury and six had a variety of cruciate and menisceal tears. The purpose of the study was to investigate if a subject's knee could be classified as "normal" or "unstable" by using just the data provided by the electrogoniometer during walking trials. These data are difficult to interpret in their time series form because they are multidimensional and in all subjects likely to exhibit subtle stride to stride variations. The method described allows the mapping of this data into an abstract two dimensional co-ordinate system, resulting in a set of trajectories which cluster together for data belonging to the "normal" group. Only two subjects, with grossly unstable knees, were judged different from normal using a level walking test protocol. Some potential reasons for this are discussed.