Medial meniscus extrusion is associated with the gait speed among the MRI-detected pathophysiologies of the knee joint in patients with knee osteoarthritis

Abstract

Purpose: Osteoarthritis of the knee (knee OA) is a joint disease involving in articular cartilage, meniscus, subchondral bone and synovium, results in the pain during walking, restriction of range of motion of the joint and disability of activity of daily living including reduction in gait speed, and is one of the representative diseases inducing the mobility impairment in middle- to older-aged populations. Although it had been considered that the pathophysiology evaluated by radiography was less associated with the clinical symptoms in knee OA, recent development of clinical studies using MRI has revealed that the pathophysiology is more associated with the clinical symptoms in knee OA. However, it is still remained unclear the MRI-detected pathophysiology of knee OA associated with gait speed in patients with knee OA. Recently, medial meniscus extrusion (MME), in addition to meniscus injury, has been known to play a critical role for the pathophysiology in knee OA. The aim of the present study was to examine the MRI-detected pathophysiology of knee OA associated with gait speed of the patients with knee OA. Methods: This study was carried out under the approval of the ethics committee of our university hospital. Patientswith medial knee OA who can walk without requiring assistance and visited our out-patient clinic for knee pain between July 2014 to July 2017participated in this study. The radiographic severity of knee OA of the subjects were evaluated by Kellgren-Lawrence (K/L) grade. The patientswere subjected to radiographic and MRI examinations on their symptomatic knee joint. and measured gait speed of 30 meters on flat floor in the hospital within the treatment period.The OA-related morphological changes of the knee joint were evaluated by the whole organ MRI score (WORMS).MME was also measured based on MRI in patients with knee OA. The self-selected gait speed of the patients was measured, and the symptomatic knee joints of them were subjected to both radiography and MRI. Multiple regression analyses adjusted for age, gender, body mass index (BMI) and pain were conducted. Results: Eighty-two patients with medial knee OA (female 65%, 69.6 years old on average) were enrolled. 14 for K/L grade 1, 14 for K/L 2, 25 for K/L grade 3 and 29 for K/L grade 4. The self-selected gait speed of the patients was 0.76 m/s on average. The cartilage lesion (p=0.048) and MME (p<0.001) were associated with the gait speed of the patients. A multiple regression analysis revealed that the MME was inversely associated with the gait speed of the patients (β2=0.568).MME, similar to the situation after menisectomy, induces the load centralization to the articular cartilage and subchondral bone, which increases the risks for destruction of articular cartilage and subchondral bone and for pain during walking. As a result, patients may reduce their gait speed to avoid knee pain. Osteophyte is revealed to be developed from the very early-stage knee OA (BMJ, 2012). We reported that MME was closely associated with the width of osteophyte on the medial side of tibia in early-stage knee OA (Arthritis Res Ther, 2017). Therefore, osteophyte formation is suggested to induce MME, which could induce walking pain and reduce gait speed, indicating that the regulation of osteophyte formation could be a novel key treatment target for early-stage knee OA. Conclusions: The MRI-detected pathophysiology of knee OA associated with gait speed was MME.