Knee replacement or knee arthroplasty is the reconstruction of the knee joint which is damaged by means of a surgical procedure. It aims in relieving pain as well as restoring joint motion and stability. Early attempts in treating severe joint destruction have made used of soft interpositional materials like human, animal, and synthetic membranes but none succeeded due to the materials which are not able to withstand the wear or even maintain the stability of the joint. Metallic implant materials have been developed beginning 1940 and the ceramic or metal prostheses since then became part of the knee reconstruction. The knee replacement refers to the usage of hinge-type prostheses. These days, all of the contemporary prostheses will be resurfacing the degraded joint surfaces and still the procedure is considered as replacement for the knee joint.
Nowadays, all of the prostheses make use of polyethylene intended for the tibial and frequently the patellar articulating surfaces. The metal-on-metal implants have been originally used however the corrosion occurred which led to the limitation of their success. Polyethylene has been constantly used for over forty years for the surgical procedure of knee replacement. Knee prostheses are being secured to the underlying bone with the utilization of acrylic resins or porous metal surface for anchoring cement.
The kind of knee being used for the above knee prosthesis depends on the client’s level of activity, strength as well as ability of knee control, weight of the client, length of the residual limb, preference of the patient, and funding. Friction is utilized in the knees for controlling the knee joint when walking. The friction is responsible to control the distance and speed of the knee bending and straightening during gait. There are knees that have mechanical friction and others have the hydraulic resistance. The computerized knees control the knee speed depending on the gait of the client. The mechanical knees are responsible for the provision of constant friction. The computerized knees and hydraulic knees are responsible for the knee speed change based on the speed of the walking client.
Manual Locking Knee – It is the most stable knee utilized in prosthetics wherein the knee is locked at the time of gait and the client releases the lock mechanism so that he or she can sit down. These knees are intended for clients having very short residual limbs or poor hip strength as well as for those losing abilities in controlling the knee.
Single Axis Constant Friction Knees – These are basic knees that can bend freely and are utilized by kids having a lower center of gravity or for clients having excellent musculature control that walks at only one speed.
Weight Activated Stance Control Knee – It is widely used and is a single axis constant friction having a braking mechanism.
Polycentric Knees – It has variable center of rotation that allows having stable gait phases. It lets the knee to have easy bending for sitting.
Hydraulic Knees – These allow adjustments for the speed of walking using hydraulics, which include either air or liquid, within the knee.
Programmable or Computerized Knees – These make use of remote handheld, programs, or software for the adjustment of one’s gait and speed in walking.