The effect of impact loading on rabbit knee joints.

Eighteen mature male Whiteland rabbits received repetitive impulse loads slightly larger than body weight (4 kp) through one knee joint for periods from 1 to 6 weeks. Mechanical compression of subchondral bone cores from impacted tibiae showed progressive increased deformation under a constant force. Cartilage degeneration occurred concurrently with alterations in the mechanical properties of the subchondral bone. The cartilage degeneration may be explained by: (i) the deleterious effect of repetitive mechanical compression, (ii) the decreased mechanical support of the underlying subchondral bone.