Arthrosis commonly affects a single compartment of the knee, but may present with two or even three compartments affected. Wear to the medial tibiofemoral compartment is ten times more common than that in the lateral tibiofemoral compartment; primary patellofemoral joint (PFJ) arthrosis is least common [1, 2]. Bicompartmental disease is present in 59% of those with gonarthrosis [3]. In one study, 40% of patients over 50 years old with knee pain had radiographic evidence of combined medial compartment and PFJ wear, 24% had isolated PFJ arthrosis, whilst only 4% had isolated tibiofemoral arthrosis [4]. Degeneration of all three compartments simultaneously is rare [2]. Consequently, removal of healthy tissue in total knee arthroplasty (TKA) is common. The anterior cruciate ligament (ACL) is present in 78% of cases of patients undergoing primary knee replacement [5]. The fundamental role of the ACL in knee stability and functional gait is well described [6]; however, regardless of its functional integrity, it is resected in almost all TKAs.
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