['Lateral osteophytes have been reported to be associated with lateral compartment disease and as such it is unclear whether medial unicompartmental knee arthroplasty should be performed if these are present.', 'Using the OARSI classification system, 0 (no osteophyte) to 3 (large osteophyte), radiographs from a series of cemented meniscal-bearing unicompartmental knee arthroplasty implanted in the setting of full-thickness lateral cartilage where lateral osteophytes were not considered a contraindication were identified and factors associated with the presence and size of lateral osteophytes, and their impact on clinical outcomes and implant survival were assessed.', 'Pre-operative radiographs from 458 knees (392 patients), independently followed up for a mean 10.5\xa0years (range 5.3-16.6), were assessed. Lateral osteophytes were present in 62\xa0% of knees with 18\xa0% scored as Grade 3. Inter-observer reliability was good (kappa\xa0=\xa00.70). The presence and size of lateral osteophytes was associated with younger age at joint replacement (p\xa0=\xa00.01) and increasing BMI (p\xa0=\xa00.01). No association was seen with gender, pre-operative status, assessed using the Oxford Knee Score (OKS), American Knee Society (AKSS) Objective or Functional Score, Tegner activity score, or size of medial tibial lesion. Subgroup analysis of Grade 3 Osteophytes revealed that these were associated with a greater degree of macroscopic ACL damage. At 10\xa0years there was no difference in function\xa0(n.s.), and at 15 years no difference in implant survival or mechanism of failure between groups (n.s.). Subgroup analysis of Grade 3 osteophytes found no significant difference in functional outcome at 10\xa0years or implant survival at 15\xa0years.'] Do lateral osteophytes represent a contraindication to medial unicompartmental knee arthroplasty : a 15-year follow-up?