A method and implant to treat anterior cruciate ligament (ACL) injuries are disclosed. The method involves advancing the insertion of the patellar ligament to the proximal tibia. The implant includes a spacer (30) which is inserted between the patellar ligament and the tibia and fixed to the tibia. The spacer decreases the angle between the patellar ligament and the tibia plateau and consequently modifies the internal joint force, restoring stability to the joint even if the ACL is ruptured. The method and implants are applicable to both human and canine patients.