Partial or Unicompartmental (or UNI) knee replacement is a procedure which involves the replacement of the medial half of the knee only.
Obviously it is indicated for less severe cases of knee osteoarthritis contained only to the medial half of the knee. These patients can still get a lot of pain during their activities , not responding well to medications and other nonoperative treatments. Often they belong to a bit younger age group than their counterparts with total knee replacement (TKR), although UNI is indicated for any age group with contained osteoarthritic change. Its main advantage compared to the TKR is that it provides a slightly better functional outcome and a more natural feeling in the knee. Most importantly, it preserves more bone stock for future re-operations (conversion to TKR) compared to a TKR. This younger, and more active age group will probably exceed the lifespan of their prosthesis (either UNI or TKR) and will require a revision or conversion) anyway.