JBJS - 2026-05-20 - Journal Article
Mild Lateral Femoral Condyle Cartilage Damage Does Not Affect the Outcomes of Medial Unicompartmental Knee Arthroplasty: A Mean 6-Year Follow-up Study.
Du M, Li Z, Jiao X, An S, Yao X, Huang J, Liu G, Cao G, Huang Y
Topics
Key Takeaway
Outerbridge grade I–II lateral femoral condyle cartilage damage does not affect Oxford Knee Score, Forgotten Joint Score, or Kujala score at mean 70.8 months after medial UKA, with 0% conversion to TKA across all groups.
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Summary
This study asked whether Outerbridge grade ≤II lateral femoral condyle cartilage damage—stratified by location (weight-bearing, posterior weight-bearing, medial side)—affects clinical outcomes or lateral compartment OA progression after medial UKA. Patients with overcorrected alignment or lateral meniscal extrusion were excluded, and outcomes included OKS, FJS, Kujala score, and serial Kellgren-Lawrence grading. No significant between-group differences were found in any functional score, and 26.3% of knees with available radiographs showed a 1-grade K-L increase in the lateral compartment regardless of baseline cartilage status.
Key Limitation
The cohort is 100% East Asian, limiting generalizability to Western populations with different BMI profiles, knee morphology, and OA patterns.
Original Abstract
BACKGROUND
The aim of this study was to ascertain whether mild cartilage damage of the lateral condyle of the femur influences the mid-term clinical outcomes of medial unicompartmental knee arthroplasty (mUKA) and exacerbates the progression of osteoarthritis in the lateral compartment.
METHODS
Patients with normal cartilage or mild cartilage damage of the lateral femoral condyle (Outerbridge grade, ≤II) who underwent mUKA between March 2016 and December 2020 were retrospectively divided into 4 groups: a normal cartilage group and a cartilage damage group that was subdivided on the basis of the damage location (weight-bearing area, posterior weight-bearing area, and medial side of the lateral condyle). Patients with postoperative overcorrection of limb alignment or preoperative lateral meniscal extrusion were excluded. Outcomes that were compared among the groups included the hip-knee-ankle angle (HKA), lateral compartment Kellgren-Lawrence (K-L) grade, Oxford Knee Score (OKS), Forgotten Joint Score (FJS), Kujala score, patient satisfaction, and complications.
RESULTS
The study included 203 knees in 177 patients (136 female patients; 177 East Asian; mean age, 68.3 ± 7.1 years) with a mean follow-up of 70.8 months (range, 48 to 106 months). The postoperative OKS, FJS, and Kujala score showed no significant differences among the groups. Mid-term full-length standing radiographs of the lower limbs were obtained for 99 of the 203 knees, with a mean follow-up of 54.1 months (range, 49 to 104 months). Of the 99 knees, 26 (26.3%) showed an increase of 1 K-L grade in the lateral compartment and 73 (73.7%) remained unchanged. Three knees (1.5%) from the normal group experienced complications, including 1 periprosthetic fracture, 1 bearing dislocation, and 1 bearing rotation, but none required conversion to TKA.
CONCLUSIONS
In patients in whom postoperative alignment is not overcorrected and preoperative lateral meniscal function is intact, mild cartilage damage (Outerbridge grade I or II) of the lateral femoral condyle does not impact the mid-term clinical outcomes of mUKA and does not exacerbate the progression of osteoarthritis in the lateral compartment.
LEVEL OF EVIDENCE
Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.