Total knee arthroplasty (TKA) consists of a surgical replacement of this joint by a prosthesis, and it is mainly carried out in cases of knee osteoarthrosis. In the postoperative period of TKA, the pain is intense and limits the mobility of patients, so the analgesia is one of the goals of the physical therapy. One of the alternatives available for pain management is the transcutaneous electrical nerve stimulation (TENS), characterized by the application of an electric pulsed current through electrodes positioned on the skin. Therefore, the present study aims to evaluate the acute effects of TENS associated with conventional physical therapy compared with conventional physical therapy on the pain level, knee range of motion and administration of morphine in the rehabilitation of patients after TKA.

The study included patients who underwent TKA surgery in the Hospital de Clínicas de Porto Alegre (HCPA) and met the study eligibility criteria. The sample was randomly divided into experimental group, which received conventional physical therapy associated with the application of TENS, and control group, which held only conventional physical therapy, both on the first day after the surgery. The pain level, the range of motion of the operated knee and the Administration of morphine.

The experimental group received TENS application held by two self-adhesive electrodes size 5x9cm positioned parallel to the lumbar spine, on the nerve roots L3, L4 and L5. TENS was applied in conventional mode, emitting a pulsed biphasic, symmetrical rectangular wave with frequency of 100 Hz and pulse duration of 100 µs, for 30 minutes. The intensity was set according to the tolerance of the patient and was gradually increased during the application. The device used was the Neurodyn II model, by Ibramed.

Subsequently, the conventional physical therapy was performed, with the use of the CPM device and performing exercises. The CPM device was used for 30 minutes, and realized continuous passive flexion and extension of the operated knee. The amplitudes of these movements were gradually increased in accordance with the tolerance of the patient. The device used was Spectra model, by Kinetec.

Then, the patients realized active exercises of plantar flexion and dorsal flexion of the ankles and adduction and abduction of the hips, isometric exercises of flexion and extension of the operated knee and active exercises of flexion and extension of the non-operated knee. All exercises were performed in 10 repetitions, with the patient positioned in the supine position in the bed.

The control group received only conventional therapy consisting of the use of the CPM device in the operated leg and the exercises in both lower limbs, identical to those performed in the experimental group.

Inclusion Criteria:

• Patients who underwent TKA surgery due to primary or secondary gonarthrosis; Both sexes; Age between 40 and 90 years.

Exclusion Criteria:

• Patients who refused to participate of the study; Indication of TKA for fractures and bone tumors; TKA review surgery; Infection during the postoperative period; Congenital anatomical alterations; Neurological disorders; Lack of understanding of commands; Sensitivity alterations in the lumbar spine or lower limbs; Decompensated heart disease or cardiac pacemaker use.

24 hours.

The exclusion criteria of the experiment included contraindications for the use of TENS: neurological disorders; lack of understanding of commands; sensitivity alterations in the lower limbs; decompensated heart disease or cardiac pacemaker use. None of the included subjects presented those conditions, therefore the risk of adverse events was zero, since they were exposed to no risk therapies and were followed by a therapist during the data collection.

The subjects had difficulty to understand Visual Analogue Pain Scale, the sample was small, and there was not a TENS placebo group, which could allow other comparisons on the effectiveness of TENS in this population.