Six subjects with lateral knee OA were excluded, and nine subjects with inappropriate radiographs were excluded from the remaining 555 subjects, leaving a total of 546 subjects (267 females and 279 males) who were included in the current analysis. A total of 561 participants (276 females and 285 males) participated in the Kanagawa Knee Study. Knee radiographs and MRI scans were performed between September 1, 2018, and August 30, 2019. Subjects with a history of knee OA, lower extremity trauma, previous surgery, rheumatoid arthritis, or consecutive visits to the hospital for knee disorders for more than 3 months were excluded. The aim of the study was to understand the epidemiology and the natural course of knee OA. Most subjects were desk workers who worked for or had retired from the Kanagawa Prefecture Government (Kanagawa is a prefecture located next to Tokyo in Japan). The Kanagawa Knee Study had a cohort consisting of at least 50 females and 50 males in their 30 s, 40 s, 50 s, 60 s, and 70 s. Kanagawa Knee Study and subject enrollment

Whether this difference is due to the cartilage or to the meniscus remains unclear. The radiographic view of the mJSW at the medial compartment can appear similar in both the extension and the Rosenberg views in some subjects, but the Rosenberg view appears narrower in others (Fig. An increasing number of reports have now shown an association between MME and a narrowing of the minimum joint space width (mJSW) at the medial compartment. Medial meniscus extrusion (MME) occurs after medial meniscus injury, but it also progresses with age, even in the absence of any obvious history of trauma. Knee OA frequently arises due to meniscus degeneration and meniscal extrusion, which induce dysfunction in the load distribution-one of the most important functions of the meniscus. The standing 45° flexion posteroanterior view (Rosenberg view) has a greater sensitivity than the standing extension anteroposterior view (extension view) for detecting OA involving the joint space width, according to a systematic review. Knee OA is typically diagnosed based on weight-bearing radiographs, which are the most widespread imaging tool for diagnosis and for detecting narrowing of the joint space width. Osteoarthritis (OA) of the knee is associated primarily with degenerative changes in the articular cartilage. The difference in the width at the medial compartment of the knee between the extension and the flexion radiographic views was more affected by medial meniscus extrusion than by cartilage thickness.The MME had a greater effect than cartilage thickness on the difference between the mJSW at the medial compartment in the extension view and in the Rosenberg view. The mJSW difference and MME were also significantly correlated, with a significantly higher correlation coefficient (0.547) than for the mJSW difference and cartilage thickness. The mJSW difference and cartilage thickness were significantly correlated at 4 subregions, with 0.248 as the highest absolute value of the correlation coefficient. The medial region of the femorotibial joint cartilage was divided into 18 subregions, and the cartilage thickness in each subregion was determined. The cartilage region was automatically extracted from MRI data and constructed in three dimensions. The mJSW at the medial compartment was measured from both the extension and the Rosenberg views, and the “mJSW difference” was defined as the mJSW in the Rosenberg view subtracted from the mJSW in the extension view. The subjects were 546 participants (more than 50 females and 50 males in their 30 s, 40 s, 50 s, 60 s, and 70 s) in the Kanagawa Knee Study. Our purpose was to determine which of the two factors, medial meniscus extrusion (MME) or cartilage thickness, had a greater effect on the difference in the minimum joint space width (mJSW) at the medial compartment between the extension anteroposterior view (extension view) and the 45° flexion posteroanterior view (Rosenberg view). Radiographs are the most widespread imaging tool for diagnosing osteoarthritis (OA) of the knee.

Knee compartments