1. Eighty-five cases of acute instability of the ligaments of the knee were treated by conservative immobilization.
2. Most of the patients were parachutists, who tore the tibial collateral ligament of the left knee during the opening-shock phase of the parachute jump.
3. The plan of treatment consists in immobilization in plaster-of-Paris, supplemented with intensive exercises for the thigh musculature.
4. End results are evaluated on the basis of the functional capacity of the knee, according to specific clinical criteria.
5. The most reliable single index of disability is the amount of quadriceps atrophy. Rehabilitation of the shrunken quadriceps invariably improves the functional capacity of the knee.
6. Recovery of stability has been very satisfactory. Ninety-five per cent. of the abduction injuries heal with less than 5 degrees of residual instability.
7. Calcification of the tibial collateral ligament is a frequent complication, but has not proved disabling.
8. Recovery of flexion and extension has been excellent.
9. Conservative immobilization has yielded excellent results in this series.