Abstract: BACKGROUND: Meniscus injury, as a significant contributing factor to knee joint degeneration, can accelerate the progression of osteoarthritis through anterior horn tears that alter joint stress distribution. Existing studies primarily focus on biomechanical changes in normal bone conditions, while the regulatory role of different bone conditions on the injury mechanism remains unclear.
OBJECTIVE: To investigate the effect of medial meniscus anterior horn transverse tears on the biomechanical differences of knee joints with varying bone conditions.
METHODS: Imaging data of the lower limb from a healthy adult were used to construct a normal knee joint model in Mimics 2017. The model was further optimized and assembled using Geomagic Studio 2017 and SolidWorks 2017, and a medial meniscus anterior horn transverse tear model was established. Material properties were defined in Ansys Workbench 2017, and bone mass reduction and osteoporosis states were simulated to generate three finite element models for biomechanical analysis. Model validation was performed through anterior drawer and axial loading tests. Subsequently, the femur was constrained, the distal tibia was fixed, and a 1 000 N axial compressive load was applied. Peak stress and strain distribution were calculated across different bone quality models.
RESULTS AND CONCLUSION: (1) Under static standing conditions, both intact and injured medial meniscus models exhibited significantly higher joint stress loading in the bone mass reduction and osteoporosis groups compared with the normal bone group. (2) In the medial meniscus anterior horn transverse tear model, stress loading on femoral cartilage and medial and lateral menisci showed a progressive increase compared with the intact model, whereas the stress on medial and lateral tibial cartilage decreased with reduced bone quality. In the injury model, stress was concentrated at the tear margins. (3) The subchondral bone region demonstrated elevated stress levels under reduced bone mass conditions, particularly after medial meniscus injury, where both strain distribution and peak equivalent stress were significantly increased, with statistically significant differences (P < 0.05). (4) This study demonstrates that medial meniscus anterior horn transverse tears, under conditions of reduced bone mineral density, exacerbate the reduction of joint contact area and local stress concentration, which may lead to increased tibia subchondral bone strain. These findings indicate an interactive biomechanical effect between bone degeneration and meniscal injury and provide a reference for selecting meniscal repair strategies according to different bone quality levels.

Key words: medial meniscus anterior horn transverse tears, osteoporosis, meniscus, finite element analysis, biomechanics