Vicente Sanchis-Alfonso, MD, PhD

Vestergaard and colleagues, in their international multicenter prospective study, analyzed 384 patients undergoing total knee arthroplasty (TKA) between 2011 and 2014. One of the questions raised in this study is whether patellofemoral osteoarthritis (PFOA) affect preoperative knee injury and osteoarthritis (OA) outcome scores in TKA. In other words, does PFOA influences outcomes as much as medial and lateral compartmental osteoarthritis do? They conclude that PFOA does not seem to affect preoperative Knee Injury and Osteoarthritis Outcome Score (KOOS) in patients with medial and/or lateral OA, challenging the importance of PFOA in TKA.

In total, 292 of 384 patients underwent patella resurfacing. That is, 76% of patients underwent patella resurfacing, while only 17.4% of patients had PFOA. This percentage of patellar resurfacing is in line with the 2019 patellar resurfacing figures (72.7% in 2019) published in the Australian Orthopaedic Association National Joint Replacement Registry (Annual Report 2020). Therefore, we are possibly over-indicating the patella resurfacing in TKA surgery. This is in accordance with the study by Hamilton and colleagues in 2017 that has demonstrated that anterior knee pain and evidence of PFOA should not be considered contraindications to mobile-bearing unicompartmental knee arthroplasty.

In my eyes, in the patellofemoral joint, patellofemoral congruence and smooth kinematics are much more important than normal articular cartilage. Patellofemoral resurfacing techniques including patellofemoral arthroplasty are indicated only in very selected cases. All of this agrees with the trends in TKA in some countries such as Sweden. According to the Swedish Knee Arthroplasty register (Annual Report 2020), the proportion of resurfacing of the patella has been reduced below 2.7% in 2019. But, what is really relevant from the clinical point of view is that a resurfacing technique is not a substitute for patellofemoral maltracking correction.