There are many reasons why knee stiffness occurs after joint replacement. In this article, ways to predict and manage such a problem are reported. Computerized records of almost 10,000 patients were reviewed to provide this information.
Stiffness was defined for this study as less than 90-degrees of knee flexion. Two groups of patients were compared. The first group had a total knee replacement (TKR) with stiffness afterwards. The second (control) group had a TKR without stiffness.
Everything about these patients was compared. For example, age, race, sex, and body mass index were compared. Range of motion before the surgery was reported. Details of the operation such as length of time and blood loss were included.
The authors report that more patients with stiff knees after TKR were younger than the control group patients. Women were affected more often than men. They had shorter patellar (kneecap) length and longer patellar tendon. These changes lead to a slightly different position of the patella (lower on the knee) called patellar baja.
Two other predictive factors of knee stiffness after TKR were lower body mass index and increased flexion angle of the femur (thigh bone). Analysis of tissue samples from around the knee showed definite differences in the repair process of the stiff knees.
The authors suggest a genetic tendency to have chemical imbalances during tissue healing may be a key feature in patients with knee stiffness after THR. Treatment to prevent this from happening may be possible in the future. Both pharmacologic and rehab approaches should be studied as potential ways to prevent disabling stiffness.