P169 - Degenerative Patellofemoral Joint does not increase failure after Unicompartmental Knee Arthroplasty

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The number of unicompartmental knee arthoplasties (UKA) has been increasing recently. With newer technology and techniques, it is unclear what factors lead to inferior results. The purpose of this study was to determine if patient with degenerative changes in the patellofemoral joint(PFJ) have inferior outcomes to patient with no changes in the PFJ, following UKA.

Methods and Materials

Forty-nine consecutive patients, who underwent UKA and had PFJ degeneration were matched by age, and sex, to patients who underwent UKA without PFJ degeneration. Failure was defined as conversion to total knee arthroplasty(TKA) or WOMAC score over 50. Other outcome scores collected at follow-up included VR12 physical(PCS) and mental(MCS) component, Lysholm, KOOS, and Tegner activity scale. This study was IRB approved.


Both groups had an average age of 66(range 39 to 85) and 39 females and 12 males. In the PFJ degeneration group, 10 knees had trochlear groove (TG) changes, 22 have patella and TG changes and 17 have patella only changes. There were 14 lateral UKA and 35 medial UKA. Average follow-up was 8.0 years in both groups. No conversions to TKA were reported in either group. WOMAC over 50 was seen in 2 patients in the PFJ degenerative group (4%) and 4 in the control group (8%) (p=0.4). At final follow-up, there was no significant difference in WOMAC (13 vs. 16;p=0.36), VR12 PCS (54 vs 55;p=0.4), VR12 MCS (55 vs 55;p=0.7), Lysholm (86 vs 86;p=0.9) or Tegner Activity scale (4.0 for both groups). In the PFJ group, there were no differences in outcomes based on the location of changes.


In this study, patients with patellofemoral degenerative changes did not have more failures or inferior outcomes. Outcomes at 8 years showed excellent results similar to a control cohort. Including patellofemoral changes as a contra-indication to UKA should be reconsidered.