A wireless force measurement system is presented in this paper. The system, which is used during the operation of Total Knee Arthroplasty(TKA), is designed to assist surgeons to determine the proper position of the knee implants and consequently enhance the success ratio of the treatment. It consists of three parts: a device to measure and transmit force data, a receiver and a terminal to display the force data in real time. The transmitter communicates with the receiver by 2.4GHz Radio Frequency (RF) signal. The system consumes no more than 17mA current with 3V voltage supply typically. So it can work with a button battery cell. Experimental results show that the performance of the system meets the requirements.