Objective. Although numerous studies have been performed to determine whether there are histologic, biochemical, biomechanical, and metabolic differences between knee and ankle cartilage, none have investigated the presence of such differences in living human cartilage. We previously developed an ultrasonic evaluation system for articular cartilage that analyzes the A-mode echogram using wavelet transformation. The current study was undertaken to determine whether the acoustic properties of living human cartilage differ between knee and ankle joints.Methods. Twenty-eight patients were subjected to ultrasonic evaluation under arthroscopy. After arthroscopic grading, the cartilage was measured using an ultrasonic probe. Two quantitative parameters were used, i.e., the maximum magnitude and the echo duration at the 95% interval of the maximum magnitude.Results. In intact cartilage, the maximum magnitude and echo duration did not differ between the knee and the ankle. In lesional cartilage, in contrast, the maximum magnitude was higher, and the echo duration was shorter, in the ankle than in the knee. These differences were statistically significant.Conclusion. Ultrasound findings could be used to judge the degree of early cartilage degeneration in vivo on the basis of objective data such as the maximum magnitude and echo duration. Because we were unable to quantitatively analyze the biochemical and biomechanical properties of the cartilage in this study, our biochemical and biomechanical findings are based only on qualitative assessment. Nevertheless, the results indicate that this ultrasonic evaluation system may be useful for elucidating the processes of articular cartilage degeneration in osteoarthritis.Osteoarthritis (OA), also referred to as degenerative joint disease, is one of the most prevalent chronic conditions, although not all joints are equally affected by the disease (1). Studies of cadavers have revealed that full-thickness cartilage defects occur ϳ20 times more often in the knee than in the ankle (2,3). Symptomatic OA with radiographic changes occurs ϳ8-9.4 times more frequently in the knee than in the ankle in patients seeking treatment (4,5). Therefore, several researchers have focused on comparing the cartilages from these 2 joints to determine whether they possess histologic, biochemical, biomechanical, and/or metabolic differences (6-10). There has been a great deal of effort, in studies using cartilage from cadavers, to elucidate the differences between these 2 joints. Indeed, such studies may help us to understand the different susceptibilities of these 2 joints and the pathogenesis of OA in general. However, none of these investigations have been conducted with living human cartilage.We previously developed a novel system for evaluating articular cartilage, in which the acoustic properties of articular cartilage are measured by introducing an ultrasound probe into the knee joint under arthroscopy (11,12). The analysis system is based on wavelet transformation of the reflex echogram from arti...
