The effects of repair, motion, and the integrity of the secondary
ligamentous restraints on healing of the medial collateral ligament were
studied in a rat model. Healing was assessed by measuring ligamentous
laxity and tensile strength. All healing ligaments were weaker and more lax
than their controls. Repair did not have a statistically significant effect
on the laxity or the strength of the medial collateral ligament. Allowing
active motion had a statistically significant beneficial effect on the
strength of the medial collateral ligament. Stability was adversely
affected by active motion if the secondary restraints had been transected;
however, when the secondary ligamentous restraints were intact, active
motion was beneficial and immobilization was harmful.