Ob j e c t i v e s : We evaluated the mid-term results of high tib-ial osteotomy in patients with medial compartment arthritis. Methods: The study included 46 patients (37 females, 9 males) with medial compartment arthritis. The patients were treated with high tibial osteotomy which was accompanied by either internal fixation (group A, 26 patients; mean age 52.4 years; range 43 to 58 years) or an external fixator (group B, 20 patients; mean age 51.7 years; range 42 to 59 years). All the patients had unilater-al involvement (31 left, 15 right). Clinical evaluations were made using the HSS (Hospital for Special Surgery) scoring system. Radiographic evaluations consisted of mechanical axis alignment, knee joint orientation angles (lateral distal femoral angle -LDFA, medial proximal tib-ial angle -MPTA), and the Insall-Salvati index. The mean follow-up was 63.9 months (range 48 to 72 months) in group A, and 57.9 months (range 49 to 63 months) in group B. Results: The mean HSS score increased from 73.4 to 85.6 in group A. Postoperatively, the mean MPTA angle was 83° and LDFA angle was 90°; the mean mechanical axis was 2 mm medially, and the mean Insall-Salvati index was 0.76. In group B, the mean HSS score increased from 72.1 to 91.2, with the mean MPTA angle being 88°, LDFA angle being 89°, the mean mechanical axis being 10 mm laterally, and the mean Insall-Salvati index being 1.1. Conclusion: We concluded that high tibial osteotomy with a circular external fixator is successful and effective in the treatment of medial compartment arthritis. Amaç: Medial kompartman artrozu olan hastalarda yüksek tibial osteotominin orta dönem sonuçlar› de¤erlendirildi. Ça l›flma plan›: Medial kompartman artrozu olan 46 hasta (37 kad›n, 9 erkek) çal›flmaya al›nd›. Bir grup hastaya yük-sek tibial osteotomi sonras› internal fiksasyon (grup A, 26 hasta; ort. yafl 52.4; da¤›l›m 43-58), bir gruba ise yüksek ti-bial osteotomi sonras› Ilizarov tipi sirküler eksternal fiksatör (grup B, 20 hasta; ort. yafl 51.7; da¤›l›m 42-59) uygu-lanm›flt›. Hastalar›n hepsinde tek tarafl› tutulum vard› (31 sol, 15 sa¤). Klinik de¤erlendirme Hospital for Special Sur-gery (HSS) skorlamas› ile, radyografik de¤erlendirme diz eklemi orientasyon (yönelim) aç›lar› (medial proksimal tibi-al aç› -MPTA ve lateral distal femoral aç› -LDFA) ve me-kanik eksen alignment (dizilim) testi ile yap›ld›. Ay r › c a , ameliyat sonras› patella yüksekli¤i Insall-Salvati indeksi kullan›larak de¤erlendirildi. Grup A'daki hastalar ortalama 63.9 ay (48-72 ay), grup B'deki hastalar 57.9 ay (49-63 ay) takip edildi. Sonuçlar: Grup A'da HSS skoru 73.4'den 85.6'ya yük-seldi. Ameliyat sonras› MPTA aç›s› ortalama 83°, LDFA aç›s› 90°, mekanik eksen ortalama 2 mm medial olarak bulundu. Ameliyat sonras› son kontrolde Insall-Salvati in-deksi ortalamas› 0.76 bulundu. Grup B'de HSS skoru or-talama 72.1 puandan 91.2'ye yükseldi. Ameliyat sonras› MPTA aç›s› ortalama 88°, LDFA aç›s› ortalama 89°, me-kanik eksen ortalama 10 mm lateral olarak bulundu. In-sall-Salvati indeksi ortalamas› 1.1 idi. Ç›kar›mlar: Medial kompartman artrozu olan hastalarda sirküler eksternal fiksatörle yüksek tibial osteotomi yak-lafl›m›n›n etkili ve baflar›l› oldu¤u sonucuna var›ld›.