The goal of this pre-post clinical trial is to compare the amplitude settings of three different frequency TENS modes (Conventional TENS, LF TENS, HF TENS) in patients who had undergone total knee arthroplasty, both with the preoperative state and with the contralateral knee. The main question it aims to answer is: Can the electrical resistance of edematous tissue be affected and change the TENS amplitude setting? Participants will be evaluated before and after surgery. For each TENS modulation the amplitude at which tingling is felt, the current is clearly felt, and is maximum tolerated and/or muscle contraction occurred, will be documented. TENS amplitudes for all three TENS modes will be compared, both with the preoperative state and with the contralateral knee.