Self-aligning knee prosthesis

A knee joint prosthesis comprising:

• a femoral component having a fixation surface configured for attaching to a femur and a sliding surface;
• a tibial tray having a fixation surface configured for attaching to a tibia and a sliding surface;
• and
• an insert that fits between the femoral component and the tibial tray when the prosthesis is installed in a subject, the insert having a femoral side and a tibial side, wherein the femoral side is shaped to slidingly interface with the surface of the femoral component during flexion of the knee and the tibial side is shaped to slidingly interface with the surface of the tibial tray,
• wherein, at regions where the surface of the femoral component interfaces with the insert during extension and an initial range of flexion of the knee, a radius of curvature (R1) of the surface of the femoral component for flexion rotation is larger than a radius of curvature (R3) of the surface of the femoral component for varus/valgus rotation, and
• wherein the insert is free to move in both the posterior-anterior direction and the medial-lateral direction with respect to the tibial tray.

A knee joint prosthesis comprising:

• a femoral component having a fixation surface configured for attaching to a femur and a sliding surface;
• a tibial tray having a fixation surface configured for attaching to a tibia and a sliding surface;
• and
• an insert that fits between the femoral component and the tibial tray when the prosthesis is installed in a subject, the insert having a femoral side and a tibial side, wherein the femoral side is shaped to slidingly interface with the surface of the femoral component during flexion of the knee and the tibial side is shaped to slidingly interface with the surface of the tibial tray,
• wherein, at regions where the surface of the femoral component interfaces with the insert during extension and an initial range of flexion of the knee, a radius of curvature (R1) of the surface of the femoral component for flexion rotation is larger than a radius of curvature (R3) of the surface of the femoral component for varus/valgus rotation,
• wherein the surface of the tibial tray is spherically curved and convex, and the tibial side of the insert is concave, and
• wherein the insert is free to move in both the posterior-anterior direction and the medial-lateral direction with respect to the tibial tray.

A joint prosthesis comprising:

• a first component having a fixation surface configured for attaching to a first bone and a sliding surface;
• a second component having a fixation surface configured for attaching to a second bone and a sliding surface;
• and
• an insert that fits between the first component and the second component when the prosthesis is installed in a subject, the insert having a first side and a second side, wherein the first side is shaped to slidingly interface with the surface of the first component during flexion of the joint and the second side is shaped to slidingly interface with the surface of the second component,
• wherein, at regions where the surface of the first component interfaces with the insert during extension and an initial range of flexion of the joint, a radius of curvature (R1) of the surface of the first component for flexion rotation is larger than a radius of curvature (R3) of the surface of the first component for rotation about an axis that is perpendicular to the coronal plane of the subject, and
• wherein the surface of the second component is spherically or toroidally curved.

A joint prosthesis comprising:

• a first component having a fixation surface configured for attaching to a first bone and a sliding surface;
• a second component having a fixation surface configured for attaching to a second bone and a sliding surface;
• and
• an insert that fits between the first component and the second component when the prosthesis is installed in a subject, the insert having a first side and a second side, wherein the first side is shaped to slidingly interface with the surface of the first component during flexion of the joint and the second side is shaped to slidingly interface with the surface of the second component,
• wherein, at regions where the surface of the first component interfaces with the insert during extension and an initial range of flexion of the joint, a radius of curvature (R1) of the surface of the first component for flexion rotation is larger than a radius of curvature (R3) of the surface of the first component for rotation about an axis that is perpendicular to the coronal plane of the subject, and
• wherein the insert is free to move in both the posterior-anterior direction and the medial-lateral direction with respect to the second component.