Locking prosthetic knee and core components therefor

A prosthetic knee can include a variable-torque magnetorheological (MR) actuator assembly or braking system, a frame and an electronics assembly or system that also serves as a mount for the knee actuator and facilitates in monitoring and controlling the operation of the knee actuator. The prosthetic knee system advantageously provides resistive forces to substantially simulate the position and motion of a natural knee joint during ambulation and/or other locomotory activities performed by the amputee. The prosthetic knee can have a series of internal blades for providing resistive forces. A locking ratchet can be used to lock knee position. A dynamic seal with a protective shim can be disposed in the knee actuator. A coil with a non-circular cross-section can be used.