Degenerative Meniscus in Knee Osteoarthritis: From Pathology to Treatment

Abstract

Knee osteoarthritis is a common degenerative joint disease characterized by chronic knee pain and disability in daily living. The lesion can involve the cartilage as well as the synovium, bone, ligaments, and meniscus, indicating a complicated pathology for knee osteoarthritis. The association with the meniscus has recently attracted much attention. Meniscal tears can initiate and progress knee osteoarthritis, with deleterious effects on the important roles of the meniscus in load distribution, shock absorption, and stability of the knee joint. Degenerative meniscus lesions are commonly observed in elderly people, but they have less impact on the prognosis of osteoarthritis. However, they are often accompanied by meniscal extrusion, which substantially decreases the hoop function of the meniscus and increases the risk of knee osteoarthritis. When surgical treatment is necessary, meniscal tears should be repaired to the greatest extent possible to preserve meniscus function. Long-term studies show better clinical outcomes and less degenerative osteoarthritis changes following meniscal repair than following partial meniscectomy. For meniscal extrusion repair, centralization techniques have been proposed that involve suturing the meniscus-capsule complex to the edge of the tibial plateau. Advancements in orthobiologics, such as platelet-rich plasma or stem cell therapy, have the potential to prevent the initiation or progression of osteoarthritis.

Keywords: centralization; medial meniscal extrusion; medial meniscus posterior root tear; meniscal repair; meniscus; osteoarthritis.

Figure 1

Scheme of knee osteoarthritis (OA) progression. In knee OA, cartilage degeneration progresses gradually based on several risk factors, including age, sex, genetic factors, bone mass index, muscle, alignment, and trauma [6]. Knee symptoms gradually progress with repeated improvement and exacerbation, and early knee OA progresses to advanced knee OA. Degenerative meniscal tears, which are typically observed in elderly people, also progress gradually, but they do not substantially affect the prognosis of OA. By contrast, meniscal extrusion, especially when followed by a medial meniscus posterior root tear, is a critical factor for the initiation/progression of knee OA, as it results in decreased meniscus coverage of the cartilage [16]. This is a quite different pathology from a simple degenerative meniscal tear [17]. Along with OA progression, synovial inflammation and osteophyte formation are commonly observed. OA; osteoarthritis; BMI; body mass index.

Figure 2

A normal meniscus in the right knee. (A) Coronal view of the normal meniscus. Arrow indicates the MM. Arrowhead indicates the LM. (B) A 3D MRI view reconstructed using SYNAPSE 3D software (Japanese product name: SYNAPSE VINCENT; FUJIFILM Corporation, Tokyo, Japan). MM, medial meniscus; LM, lateral meniscus; MTP, medial tibial plateau.

Figure 3

An extruded medial meniscus in the right knee. (A) Medial meniscal extrusion was confirmed in a coronal view (white arrow). Cartilage defects were observed in the medial compartment. (B) The 3D MRI view shows the cartilage defect in the MFC (white arrowhead). (C) Arthroscopic findings indicate decreased meniscal coverage of the MTP and cartilage defects in the MFC and the MTP. (D) The 3D MRI view shows extrusion of the MM (white arrow) and a cartilage defect in the MTP (black arrowhead). MM, medial meniscus; LM, lateral meniscus; MFC, medial femoral condyle; MTP, medial tibial plateau.