![]() The asymmetry of the natural bony anatomy maintains the alignment of the joint and ligamentous tension. The sagittal alignment of the proximal tibia is sloped posteriorly approximately 5 to 7 degrees. The varus position of the proximal tibia, along with the offset of the hip center of rotation, results in the weight-bearing surface of the tibia being parallel to the ground. The proximal tibia is oriented to 3 degrees of varus. The anatomic axis of the femur, defined by a line bisecting the femoral shaft, is 6 degrees valgus to the mechanical axis of the femur and 9 degrees valgus to the vertical axis. ![]() The mechanical axis of the femur, defined by a line drawn from the center of the femoral head to the center of the knee, is 3 degrees valgus to the vertical axis. Menisci are interposed in the medial and lateral compartments between the femur and tibia which act to protect the articular cartilage and support the knee. ![]() Articular cartilage covers the femoral condyles, tibial plateaus, trochlear groove, and patellar facets. The capsule surrounds the entire joint and extends proximally into the suprapatellar pouch. The stability of the knee joint is provided by the congruity of the joint as well as by the collateral ligaments. There are 3 separate articulations and compartments: medial femorotibial, lateral femorotibial, and patellofemoral. It is comprised of the distal femur, proximal tibia, and the patella. The knee is a synovial hinge joint with minimal rotational motion. Furthermore, advances have been made in fixation techniques and wear properties of the bearing surface which positively affects the longevity of the knee replacement. Since this breakthrough in prosthesis in the 1970s, the design has evolved to focus on replicating the anatomy and normal function of the knee joint. This was subsequently replaced with a prosthesis that replicated the shape of the distal femur, preserved the collateral and cruciate ligaments, and consisted of a plastic bearing on the tibia. While this produced satisfactory results, there was a high rate of failure and poor long-term outcome due to the failure of reproducing the natural kinematics of the knee joint. ![]() In the 1950s, a hinged prosthesis was designed to replace the femur and tibia, as well as the stabilizing ligaments surrounding the knee. This design did not produce favorable results and was eventually replaced with metal implants in the 1930s. The history of TKA dates back to the mid to late 1800s when the first implants were made from ivory and fixed to the bone using a combination of colophony and plaster of Paris. The primary goal of either surgery is durable pain relief with the improvement of functional status. Additionally, partial knee arthroplasty (PKA) is an excellent treatment option for individuals with symptomatic osteoarthritis localized to 1 compartment of the knee and who have failed conservative treatment. Total knee arthroplasty (TKA) is an excellent treatment option for individuals with symptomatic osteoarthritis in at least 2 of the 3 compartments of the knee and who have failed conservative treatment. It is more commonly referred to as a total knee replacement and is a very reliable procedure with predictable results. Knee arthroplasty is a reconstruction of the knee joint. ![]()
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