Unicompartmental knee arthroplasty vs. high tibial osteotomy for medial knee osteoarthritis (UNIKORN): a study protocol of a randomized controlled trial

Juuso Siren, Lasse Rämö, Mikko Rantasalo, Olli Komulainen, Noora Skants, Aleksi Reito, Jussi Kosola, Jan Lindahl

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Background: Medial knee osteoarthritis (OA) is a common health problem resulting in knee pain and limiting patients’ physical activity. After failed conservative treatment, unicompartmental knee arthroplasty (UKA) and high tibial osteotomy (HTO) are possible surgical treatment options for this condition. There is a paucity of high-quality evidence in the literature comparing objective and subjective outcomes of these procedures. Also, there is no common agreement on whether these procedures provide comparable results in late-stage medial knee OA patients. Methods: We will perform a prospective randomized controlled trial comparing HTO and UKA in patients with late-stage medial knee OA. 100 patients with isolated medial knee OA (KL III–IV) are assigned to either UKA (n = 50) or HTO (n = 50) procedure in patients 45–65 years of age. Our primary outcome will be KOOS5 at one year postoperatively. Secondary outcomes include OARSI physical assessment, length of stay, wearable activity watch, radiographs (OA progression according to Kellgren-Lawrence classification), patient-reported outcomes (KOOS subscales, pain visual analog scale [VAS], Lysholm, and Oxford knee scores), and adverse events (conversion to total knee arthroplasty, surgery-related complications, need for revision surgery) outcomes. Our hypothesis is that neither of the interventions is superior as measured with KOOS5 at 12 months. Ethics and dissemination: The institutional review board of the Helsinki and Uusimaa Hospital District has approved the protocol. We will disseminate the findings through peer-reviewed publications. Trial registration: NCT05442242. Registered on 7/1/2022.

Original languageEnglish
Article number256
Issue number1
Publication statusPublished - 2023
Publication typeA1 Journal article-refereed


  • Activity monitoring
  • High tibial osteotomy
  • Intention to treat
  • Knee osteoarthritis
  • Randomized controlled trial
  • Superiority trial
  • Unicompartmental knee arthroplasty

Publication forum classification

  • Publication forum level 1

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Pharmacology (medical)


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