Knee surgery basics

Since the first knee replacement surgery in 1968, there has been enormous progress in improving the surgical techniques and medical devices used to replace damaged bone and cartilage in the knee.1

Let's first review some of the basic surgical steps that almost all knee replacements have in common:

Bone preparation. During this step, the damaged cartilage surfaces at the ends of the femur (the thigh bone) and the tibia (the larger of the two lower leg bones) are removed along with a small amount of underlying bone.

Install the metal implants. During this step, carefully selected metal components are fitted to the prepared bones of both the femur and tibia.

Insert a spacer. During this step, a medical-grade, plastic spacer is attached to the lower, metal tibial component, creating a smooth surface for upper, metal femoral component to slide against as the knee moves.

All of the progress in knee replacement surgery and implant technology also means that today's informed patients face a wide array of surgery and implant choices, as well as a potentially confusing vocabulary of terms including total replacement, patient-matched instruments, partial replacement, robotic-assisted surgery, minimally invasive techniques and more. Let's explore and explain some of these:

Types of knee replacements

Total knee replacement

Total knee replacement (sometimes shortened to TKR) is a surgical procedure to replace the ends of the femur and the tibia that have been damaged by osteoarthritis or other conditions, with prosthetic devices that duplicate the motion and weight-bearing abilities of the original joint.

In Total knee replacement, the prosthesis is comprised of several parts:

Implant components

  • The tibial component includes a metal base and a plastic insert. Together these replace the top of the tibia (shin bone) and the cartilage in the knee to provide half of the new joint's bearing surface.
  • The femoral component replaces the bottom of the femur (the thigh bone). This component also replaces the groove in the natural knee where the patella or kneecap rides.
  • The patellar component replaces the surface of the knee cap, which rubs against the femur. The patella protects the joint, and the resurfaced patellar button will slide smoothly on the front of the joint. In some cases, surgeons do not resurface the patella.3

Partial knee replacement

Replacing only what is damaged

A partial knee replacement (also known as Unicompartmental, or UKR) may be recommended if arthritic damage is confined to only one area of your knee. Because a partial knee replacement doesn't extend across the entire joint, the damaged portion of the knee is replaced while the supporting ligaments vital to knee stability may be spared.

Candidates for partial knee replacement generally have osteoarthritis limited to one compartment of the knee; this group makes up roughly 35%+ of people dealing with knee pain.4,5

Partial knee replacement implant components are similar to Total Knee Replacement, but the implants replace only part of the tibial and femoral surfaces.

Knee surgery techniques and technologies

Traditional knee surgery may be enhanced with advanced techniques, tools and technologies. Since the earliest attempts at surgical knee replacement, there has a wide range of technological innovation. Medical imaging, more precise surgical tools, and the design and construction of the implants themselves have all come a long way since the first replacement surgery some 50 years ago. The intended benefit for patients is shorter recovery time, less post-surgical pain, longer lasting implants and more natural-feeling, 'knee-like' motion of the prosthesis.

Minimally invasive knee surgery

Whether you are having a total or a partial knee replacement, you may be a candidate for what's known as minimally invasive surgery. This surgical technique uses specially designed instruments that help minimize disruption of the soft tissues in the joint during your surgery, with the aim of reducing post-operative pain and speeding the recovery process. A primary cause of post-surgical pain is the swelling that occurs any time the soft tissue of the body is cut or otherwise manipulated. Minimally invasive surgery may also result in a smaller incision scar.

Robotic-assisted surgery - CORI Surgical System

Some surgeons use robotic assistance as part of their knee replacement surgery. This assistance is designed to optimize the accuracy of bone preparation, implant positioning, and soft tissue balancing both in the planning stage and during the surgery itself. Robotic assistance leaves the surgeon in complete control of the operation while helping the implant to remain stable and properly aligned throughout the knee's full range of motion.

Want more detail on the CORI System? Visit our CORI pages for technical information, and references to scientific studies on its use and effectiveness.

Patient matched technology - VISIONAIRE technology

Like robotic-assisted surgery, patient matched technologies such as VISIONAIRE Cutting Guides are intended to help make sure your implant is correctly sized and aligned based on your unique physical needs.

Created using your own MRI and X-ray images, VISIONAIRE Cutting Guides help to direct the surgeon's saw to assure that all bone cuts are precisely aligned. Standard cutting guides require an aligning device known as an intramedullary (IM) rod which is inserted into the core of the femur bone. VISIONAIRE Cutting Guides eliminate the need for the IM Rod and several other surgical steps. This may help reduce the potential for infection, and shorten the overall time you spend under anesthesia.

Want more detail on Visionaire technology? Visit our Visionaire pages for technical information, and references to supporting studies.

Important safety notes

Individual results of joint replacement vary. Implants are intended to relieve knee pain and improve function, but may not produce the same feel or function as your original knee. There are potential risks with knee replacement surgery such as loosening, wear and infection that may result in the need for additional surgery. Patients should not perform high impact activities such as running and jumping unless their surgeon tells them that the bone has healed and these activities are acceptable. Early device failure, breakage or loosening may occur if a surgeon's limitations on activity level are not followed.


  1. American Academy of Orthopaedic Surgeons website, accessed March 7, 2017:
  2. Willis-Owen, Charles, et al, Unicondylar knee arthroplasty in the UK National Health Service: An analysis of candidacy, outcome and cost efficacy, The Knee 16, 473-478,, January 3, 2009
  3. Liddle, A.D., Pandit, H., Et al, Optimal Usage of Unicompartmental Knee Arthroplasty, The Bone & Joint Journal,, November 3, 2015
  4. Willis-Owen, Charles, et al, Unicondylar knee arthroplasty in the UK National Health Service: An analysis of candidacy, outcome and cost efficacy, The Knee 16, 473-478,, January 3, 2009
  5. Liddle, A.D., Pandit, H., Et al, Optimal Usage of Unicompartmental Knee Arthroplasty, The Bone & Joint Journal,, November 3, 2015

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