Does Edema Affect the Adjustment of TENS Amplitude

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.

Inclusion Criteria: * Age ≥ 40 years * Patients undergoing unilateral total knee arthroplasty Exclusion Criteria: * Patients with scars in any of both knee areas * Patients who have previously had surgery on the control leg * Patients undergoing surgery due to trauma or cancer * Patients with sensory impairments * Patients with excessive effusion and edema in the knee joints before the surgery (eg. Inflammatory arthropathy, gonarthrosis exacerbation, etc.) * Mental impairment, or poor general health status that would interfere with assessments during TENS application. * Any contraindication for TENS (allergy to the TENS electrodes, skin conditions or skin sensation impairment in the areas where the electrodes will be placed, pacemaker or other implanted electrical device, epilepsy, pregnancy)