Most developed countries now have aging societies, and the associated increases in the elderly population have led to an increase in the prevalence of chronic diseases. Degenerative knee arthritis is one such disease, in which pain is experienced when the knee is moved. Knee joint degeneration is detected using technological methods in addition to consultation and palpation by a doctor. Clinically, the degree of knee injury is often determined with the aid of radiological medical equipment, but these have safety considerations such as excessive radiation doses. The desire to improve the convenience of operating on the knee joint and reduce safety concerns has prompted the digitization of medical aids, which can decrease the burden on doctors and other medical professionals. In this paper, we propose an innovative knee auscultation device that is designed to reduce noise due to friction when measuring knee sounds. A wireless sound and posture detection system has also been constructed with inertial sensors and directional microphones. The system can simultaneously record low-intensity knee sounds and knee flexion angles. To improve the wearing comfort during measurement, wireless transmission technology is used to reduce wired connections. The prototype design and testing of the system have been completed, and the system could be used for long-term knee health monitoring and clinical preventive medicine in the future.