Some individuals can stabilize their knees following anterior cruciate liga
ment rupture even during activities involving cutting and pivoting (copers)
, others have instability with daily activities (non-copers). Movement and
muscle activation patterns of 11 copers, ten non-copers and ten uninjured s
ubjects were studied during walking and jogging. Results indicate that dist
inct gait adaptations appeared primarily in the non-copers. Copers used joi
nt ranges of motion, moments and muscle activation patterns similar to unin
jured subjects. Non-copers reduced their knee motion, and external knee fle
xion moments that correlated well with quadriceps strength. Non-copers also
achieved peak hamstring activity later in the weight acceptance phase and
used a strategy involving more generalized co-contraction. Both copers and
non-copers had high levels of quadriceps femoris muscle activity. The reduc
ed knee moment in the involved limbs of the non-copers did not represent "q
uadriceps avoidance" but rather represented a strategy of general co-contra
ction with a greater relative contribution from the hamstring muscles.