Scientists have used a wide variety of motion capture methods to discover these altered patterns of motion after ACL rupture and reconstruction. The study of alterations in joint motion is referred to as kinematics.
Dynamic imaging such as high-speed X-rays, fluoroscopy, or MRIs taken while the patient is moving have been used in these studies. The information gathered has helped us understand changes in knematics after ACL injury.
Changes in the contact patterns of the joint seem to be what leads to arthritis later. The cartilage cells try to adapt to changes in their metabolism from these new loads.
Studies at the cellular level show that tissue stress affects the organization of cartilage. The cartilage reacts and adapts to changes in load as much as possible. But they may not be able to withstand compressive or shear forces.
The average patient doesn't have access to such study methods. You may not be aware of changes going on in your knee until pain, stiffness, or swelling occur. Until further studies offer specific solutions, experts advise staying active and keeping up on strength training of the muscles around the knee.