We propose a peak detection and frequency measurement circuit for integration at interface with a triboelectric nanogenerator (TENG). By measuring the frequency and the peak voltage at the output of TENG, the applied force is predicted. We propose a sample and hold peak detector circuit with a reset signal for continues peak detection. The control logic also generates a trigger signal for analog to digital conversion of the peak voltage to the digital domain. At the same time, the frequency is recorded by counting the number of peaks in a defined time period. The circuit simulations in 180 nm CMOS technology demonstrate peak conversion with 8-bit resolution in a 1 V voltage range with 500 nW power consumption. The proposed design is amenable for integration in a self-powered load sensing system in smart knee implant after total knee replacement(TKR) surgery.