Biomechanical control of knee alignment: some insights from a new paradigm.

A chondral growth force response curve suggests how longitudinal bone growth at growth plates responds to compression loads. Between zero load and some limit, increasing loads increase growth. Above that limit, further increases in compression can decrease growth, and large enough compression loads can stop it. In the valgus-varus sense, in a child's knee these responses would tend to make its growth plates and the joint align perpendicularly to the time-averaged compression loads on them and tend to correct small malalignments but make large malalignments become worse. Combined with effects of the regional acceleratory phenomenon, in children these responses can also explain some cases of postfracture knee valgus and its subsequent spontaneous correction.