The human knee fairly neatly can be described as three parts: 1) the inside (medial compartment), 2) outside (lateral compartment) and 3) the articulation between the knee cap and femur (patellofemoral compartment). When performing a knee replacement typically all three compartments are addressed and a total knee replacement is performed. It is also possible to perform a replacement of just one (unicompartmental replacement) or two compartments (bicompartmental replacement). Single compartment or partial knee replacements are attractive because they are less intrusive and typically have a fuller and faster recovery. Also, the feel of the knee is more natural since all the ligaments and much of then natural knee is preserved.
For partial knee replacements to be successful a carefully designed implant is necessary. Also, the technique of surgery is very demanding as the implant much match the remaining natural knee exceptionally well to work well. The Persona Knee is a modern generation partial knee replacement that works well.