Abstract. Objective. Explore whether high tibial osteotomy (HTO) changes knee contact forces and to explore the relationship between the external knee adduction moment (EKAM) pre and 12 months post HTO. Methods. Three-dimensional gait analysis was performed on 17 patients pre and 12-months post HTO using a modified Cleveland marker-set. Tibiofemoral contact forces were calculated in SIMM. The scaled musculoskeletal model integrated an extended knee model allowing for 6 degrees of freedom in the tibiofemoral and patellofemoral joint. Joint angles were calculated using inverse kinematics then muscle and contact forces and secondary knee kinematics were estimated using the COMAC algorithm. Paired samples t-test were performed using SPSS version 25 (SPSS Inc., USA). Testing for normality was undertaken with Shapiro-Wilk. Pearson correlations established the relationships between EKAM1 to medial KCF1, and EKAM2 to medial KCF2, pre and post HTO. Results. Total knee contact force peak 1 significantly reduced from 2.6 x body weight pre-HTO to 2.3 x body weight 12-months post-HTO. Medial contact force peak 1 significantly reduced from 1.7 x body weight pre-HTO to 1.5 x body weight 12-months post-HTO. Second peak lateral knee contact force significantly increased from 0.9 body weight pre-HTO to 1.1 x body weight 12-months post-HTO. Furthermore, this study found very strong correlations between EKAM1 and medial KCF1 pre-HTO (r=0.85) as well as post-HTO (r=0.91). There was a significantly moderate relationship between EKAM2 and medial KCF2 pre-HTO (r=0.625). Conclusion. HTO significantly reduced overall and medial KCF during the first half of stance whilst increasing second half of stance peak lateral knee contact force. This study demonstrated a strong relationship between EKAM peaks and respective medial KCF peaks, supporting the usefulness of EKAM as a surrogate measure of medial compartment tibiofemoral contact forces. This demonstrates HTO successfully offloads the tibiofemoral joint overall, as well as offloading the medial compartment

The patellofemoral joint is an important source of symptoms in osteoarthritis of the knee. We have used a newly designed surgical model of patellar strengthening to induce osteoarthritis in BALB/c mice and to establish markers by investigating the relationship between osteoarthritis and synovial levels of matrix metalloproteinases (MMPs). Osteoarthritis was induced by using this microsurgical technique under direct vision without involving the cavity of the knee. Degeneration of cartilage was assessed by the Mankin score and synovial tissue was used to determine the mRNA expression levels of MMPs. Irrigation fluid from the knee was used to measure the concentrations of MMP-3 and MMP-9. Analysis of cartilage degeneration was correlated with the levels of expression of MMP.

After operation the patellofemoral joint showed evidence of mild osteoarthritis at eight weeks and further degenerative changes by 12 weeks. The level of synovial MMP-9 mRNA correlated with the Mankin score at eight weeks, but not at 12 weeks. The levels of MMP-2, MMP-3 and MMP-14 mRNA correlated with the Mankin score at 12 weeks. An increase in MMP-3 was observed from four weeks up to 16 weeks. MMP-9 was notably increased at eight weeks, but the concentration at 16 weeks had decreased to the level observed at four weeks.

Our observations suggest that MMP-2, MMP-3 and MMP-14 could be used as markers of the progression of osteoarthritic change.