Assessing joint line obliquity in valgus-producing high tibial osteotomy: A scoping review of the literature.

Background: The variance in knee joint line obliquity (KJLO) measurement methods and radiographic techniques may contribute to the controversy on clinical consequences of KJLO after high tibial osteotomy (HTO). Purpose: To summarize currently used KJLO measurement methods, including their measurement reliability, and the radiographic techniques used in valgus-producing HTO. Methods: The databases PubMed, Embase, and Web of Science were searched from inception up to May 2023, to identify articles that measured KJLO on radiographs in valgus-producing HTO. Results: Thirty clinical articles were included. There were five different KJLO measurement methods reported, including joint line orientation angle by femoral condyles (JLOAF), joint line orientation angle by middle knee joint space (JLOAM), joint line orientation angle by tibial plateau (JLOAT), Mikulicz joint line angle (MJLA), and medial proximal tibial angle (MPTA), of which the JLOAT was the most commonly used. KJLO was measured on anteroposterior full-length standing radiographs with either single-leg or double-leg patient stance position, with no standardized bipedal distance on double-leg stance radiographs. Moderate-to-excellent measurement reliability was reported for intraobserver and interobserver MPTA, and good-to-excellent for intraobserver JLOAT and JLOAM and for interobserver JLOAT, JLOAM, and MJLA. Conclusion: There is no consensus on how to measure KJLO or on which radiographic technique should be used. When measuring joint line orientation angles on anteroposterior full-length double-leg stance radiographs, controlling the bipedal distance with feet together is suggested when possible. Future research is needed to determine the measurement differences between the five KJLO measurement methods and to identify the preferred, ideal one.