PKR is an abbreviation of 'partial knee replacement'.
The concept of 'compartments'
The knee is considered to have three articular 'compartments' - two are where the tibia makes contact with the rounded ends of the femur (tibio femoral compartments) and one where the patella makes contact with the concave groove of the femur (patellofemoral compartment). A partial knee replacement may involve any one of these compartments.
Patient relevant outcomes of unicompartmental versus total knee replacement: systematic review and meta-analysis. Wilson HA, Middleton R, Abram SGF, Smith S, Alvand A, Jackson WF, Bottomley N, Hopewell S and Price AJ. BMJ. 2019; 364: l352.