Three-dimensional finite-element analysis of aggravating medial meniscus tears on knee osteoarthritis

The biomechanical change during the medial meniscus damage in the process of knee osteoarthritis has not been explored. The purpose of this study was to determine the effect of aggravating medial meniscus degenerative tear on the progress of knee osteoarthritis through the finite-element simulation method.

The three-dimensional digital model of a total-knee joint was obtained using a combination of magnetic resonance imaging and computed tomography images. Four types of medial meniscus tears were created to represent the aggravating degenerative meniscus lesions. Meniscectomy of each meniscal tear was also utilized in the simulation. The compression and shear stress of bony tissue, cartilage, and meniscus were evaluated, and meniscus extrusion of the healthy knee, postinjured knee, and postmeniscectomy knee were investigated under the posture of balanced standing.

Based on the results of finite-element simulation, the peak shear principal stress, peak compression principal stress, and meniscus extrusion increased gradually as the meniscus tears' region enlarged progressively (from 7.333 MPa to 15.14 MPa on medial femur and from 6 MPa to 20.94 MPa on medial tibia). The higher stress and larger meniscus extrusion displacement in all tests were observed in the flap and complex tears. The oblique tears also had a biomechanical variation of stress and meniscus extrusion in the knee joint, but their level was milder. Both the peak value of the stress and meniscus displacement increased after the meniscectomy.

In contrast to the damaged hemijoint, the stress applied on the healthy lateral hemijoint increased. The change of biomechanics was more obvious with the aggravation of meniscus injury. The advanced degenerative damage resulted in increasing stress that was more likely to cause symptomatic clinical manifestation in the knee joint and accelerate the progress of osteoarthritis. Moreover, we found that the meniscus injury caused higher stress concentration on the contralateral side of the joint. We also discovered that the meniscectomy can lead to more serious biomechanical changes, and although this technique can relieve pain over a period of time, it increased the risk of osteoarthritis (OA) occurrence.

It is clear that the meniscal lesions can cause osteoarthritic knee, but the biomechanical change during the meniscus damage period has not been explored. We have evaluated the variation of stress during the aggravating medial degenerative meniscus tears and the relationship in the process of knee OA through finite-element simulation. This study does favour to obtain a better understanding on the symptoms and pathological changes of OA. It also may provide some potential directions for the prophylaxis and treatment of OA.