Closing the Total Knee Replacement in Full Flexion
When patients express dissatisfaction after undergoing total knee replacement, one common complaint is a perceived “stiffness” in the joint, which limits motion and impairs normal activities. This stiffness is expected, given the extensive nature of knee surgery, which the body perceives as a significant injury requiring robust healing mechanisms. Unfortunately, the final stage of this healing process often involves the formation of inflexible scar tissue. In post-surgery rehabilitation, the goal is to counteract this propensity for stiffness by actively and passively moving the knee joint, hoping to achieve sufficient motion before scar tissue becomes dense enough to restrict movement. It becomes a race against time.
A logical concept emerges: If the knee remains in continuous, full motion, it cannot become stiff or scarred. However, early and vigorous flexion presents a challenge. Traditionally, the knee wound is closed with the leg straight, making surgeons hesitant to employ vigorous early flexion fearing the wound may split open. Standard protocols typically advocate for a gradual increase in flexion to minimize the risk of wound dehiscence. In the past, Continuous Passive Motion (CPM) machines were used, initiating motion a day after surgery for 2 to 3 hours and gradually increasing the flexion angle by 10 degrees per day. However, studies have shown that this protocol does not offer significant rehabilitation benefits, leading surgeons to abandon the use of CPM machines. Attaining sufficient flexion has been left to the patient, with adequate pain control and guidance from a physical therapist. Unfortunately, scar tissue often wins the race, resulting in knee stiffness.