Knee Replacement FAQs
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Q. What, exactly is “replaced” in 
knee replacement?
A. The worn ends of the femur ( thigh bone), tibia (shin) and patella (knee cap) are removed with a saw and replaced with metal and plastic.
More on Knee Replacement Surgery
Q. What, is a Knee Replacement Implant made of?
A. Implants are typically made of a combination of Cobalt Chrome and/or Titanium metals and UHMWPE (ultra-high-molecular-weight polyethylene) plastic.
More on Knee Implants.
Q. Are there different kinds of implants?
A. Yes! There are many types of 
knee implants that fit into broad categories related to their interaction with the remaining natural soft tissue. For example a CR or Cruciate Retaining knee implant is designed to work with the PCL (posterior cruciate ligament) intact. Other types of implants are designed to work without it. In addition, there are many manufacturers of implants which create several brands of knees in each of the broad categories. Surgeons have many, many choices.
More onTypes of Knee Implants.
Links to Implant Manufacturers.
Q. How long will my Knee Replacement last?
A. There are many studies on this topic and the actual time an implant will survive before needing revision will vary on a case by case basis. Several studies demonstrate greater than 90% survivorship at 15 years (1)
Q. How are the implants held in place?
A. 
Total knee replacement implants implants are secured to the bone either with a special polymeric compound (”bone cement”) or are “press-fit” into place. Press fit implants have rough or porous undersurfaces into which bone will grow.
More on Knee Implants.
Q. What is a Uni (or Partial or Half-knee) Replacement?
A. A “Uni” or unicompartmental knee replacement replaces only the medial (inner) or lateral (outer) half of the knee joint (the tibio-femoral joint). The knee cap or patella is not replaced.
More on Unicompartmental Knee Replacement.
Q. What is MIS or Minimally Invasive Knee Replacement?
A. MIS or Minimally Invasive Knee Replacement is like standard knee replacement except that the incision is smaller, and care is taken not to resect the quadriceps muscle (also known as “quad sparing”). Also, the patella is not “everted” or “flipped” over This is all intended to result in less trauma and speed recovery.
More on Minimally Invasive Knee Replacement.
Q. What about recovery, pain etc?
A. Every case is unique and this discussion is best left for a medical professional. You can read about the experience of other recipients at a very interesting discussion forum at Robin’s Total Knee Replacement.
References
1) Dixon MC, Brown RR, Parsch D, Scott RD. Modular fixed-bearing
total knee arthroplasty with retention of the posterior cruciate
ligament. A study of patients followed for a minimum of fifteen years.
J Bone Joint Surg Am.
2005 Mar;87(3):598-603
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