Capacitive–resistive electric transfer (CRet) therapy is widely used in physical rehabilitation and sports medicine to treat muscle, ligament, tendon, and joint pathologies. It operates through the transmission of radiofrequency energy (typically around 448–500 kHz, as in the Wintecare T-Plus) and produces both thermal and non-thermal biological effects. However, the specific temperature changes in deep joint structures, such as the knee capsule and intra-articular space, had not been directly measured before this work.
This cadaveric study, conducted jointly by researchers from the Universitat Internacional de Catalunya (Barcelona) and the Universidad de Zaragoza, aimed to quantify how various CRet treatment protocols—distinguished by mode (capacitive vs resistive) and power level (high vs low)—affect temperature distribution and current flow in the superficial, capsular, and intra-articular tissues of the knee. The purpose was to differentiate thermal from non-thermal physiological effects under conditions that mimic clinical Tecar therapy. By doing so, the investigators sought to identify which energy settings are most appropriate for acute inflammatory conditions (where excessive heating is undesirable) versus chronic fibrotic or stiff joint states (where heat-induced viscoelastic changes may aid recovery).
This cross-sectional cadaveric study analyzed the effects of capacitive–resistive electric transfer (CRet) application on the knee using the T-Plus device by Wintecare. The investigation was carried out at the Universitat Internacional de Catalunya (UIC) and approved by its ethics committee (CER, CBAS 2019-07). The study followed the Declaration of Helsinki, with specimens obtained through UIC’s body donor program.
The sample consisted of five fresh-frozen cadavers (four men, one woman; mean age ≈ 70 years), providing a total of ten lower limbs. Each limb underwent four separate CRet interventions, representing all combinations of treatment mode and power level:
Each application lasted 5 minutes, administered by a licensed physiotherapist experienced with CRet therapy. The movable electrode was applied to the posterior region of the knee, while the return electrode was placed on the abdomen to complete the circuit. The HPC and LPC settings targeted superficial, water-rich tissues, while HPR and LPR focused on deeper, more resistive structures such as ligaments and joint capsule.
To simulate real clinical handling, the therapist performed dynamic gliding movements with consistent pressure during treatment. For resistive applications, conductive cream was applied to ensure optimal current transmission; for capacitive ones, it was omitted.
Temperature monitoring was conducted invasively using calibrated thermocouples (Hart Scientific PT25 5628-15) positioned under ultrasound guidance at three depths:
Temperature data were recorded every minute during treatment and again 5 minutes after completion. The current flow for each protocol was determined from voltage and impedance readings, while impedance was verified before each session to ensure accurate delivery.
All data were statistically analyzed using SPSS v22, calculating reliability via intra-class correlation coefficients (ICC > 0.9), and testing intra- and inter-protocol differences using Friedman, Wilcoxon, Kruskal–Wallis, and Mann–Whitney U tests, with p < 0.05 considered significant.
All four CRet protocols produced measurable changes in temperature and electric current transmission through the knee’s superficial, capsular, and intra-articular structures. The baseline temperatures were comparable across groups, confirming consistency prior to treatment.
The High-Power Capacitive (HPC) setting generated the most significant surface heating, with temperature increasing by ≈17.3 °C (84 %) from baseline to reach ≈38 °C after 5 minutes. The High-Power Resistive (HPR) protocol produced a slightly smaller rise (≈13.6 °C; 65 % increase) but maintained heat longer after treatment. By contrast, Low-Power Capacitive (LPC) and Low-Power Resistive (LPR) settings induced only modest surface heating (increases of 7.4 °C / 35 % and 3.4 °C / 17 %, respectively).
At the level of the joint capsule, HPR produced the greatest thermal change—an increase of ≈11.4 °C (49 %) from baseline, followed by HPC (≈3.6 °C; 16 %). LPC and LPR achieved minimal heating (≈2–3 °C). All comparisons involving HPR were statistically significant (p < 0.001). Importantly, even the low-power conditions demonstrated a detectable current flow through the capsule despite limited heat accumulation.
Within the knee joint cavity, HPR again achieved the largest rise—≈7.1 °C (34 %), followed by HPC (≈3.5 °C; 18 %). LPC slightly reduced intra-articular temperature (–0.4 °C), and LPR produced only a minor increase (≈0.7 °C; 4 %). The differences between HPR and all other protocols were statistically significant (p < 0.001).
Electrical current measurements mirrored the thermal gradient. The average current amplitudes were:
Even in low-power modes, measurable current passed through deep tissues—confirming non-thermal bioelectrical activity consistent with cell-stimulation and proliferative effects previously reported in vitro.
Overall, high-power modes produced marked thermal and electrical effects, particularly HPR, which heated deep joint structures most effectively. Low-power modes generated minimal heat yet maintained current flow—supporting their potential for acute-phase or inflammatory applications where deep tissue warming is not desired.
This cadaveric study demonstrated that capacitive–resistive electric transfer (CRet) therapy, when applied using the Wintecare T-Plus device, generates distinct thermal and non-thermal effects in knee tissues depending on the selected mode and power level.
The low-power settings (LPC and LPR) produced minimal heat in both capsular and intra-articular regions yet maintained consistent electric current flow through the tissue. This indicates the potential for non-thermal cellular stimulation—useful during acute inflammatory or early rehabilitation phases, where temperature elevation could aggravate swelling or tissue stress.
In contrast, the high-power protocols (HPC and HPR) induced substantial and graded heating responses. The High-Power Resistive (HPR) setting yielded the most pronounced deep-tissue heating—raising capsular temperature by ~11 °C (49 %) and intra-articular temperature by ~7 °C (34 %)—alongside the highest current intensity (≈0.2 A). These characteristics make HPR especially suitable for chronic or fibrotic conditions, where controlled hyperthermia supports collagen extensibility, viscoelastic remodeling, and improved circulation.
Meanwhile, High-Power Capacitive (HPC) primarily affected superficial tissue layers, making it advantageous for enhancing muscle pliability and blood flow in more superficial structures.
The authors concluded that this dual behavior—non-thermal electrical activity at low power and deep thermogenesis at high power—provides the physiological basis for Tecar therapy’s adaptability across both acute and chronic stages of rehabilitation. These results support the clinical rationale for using resistive versus capacitive modes selectively, depending on tissue depth and therapeutic goal, while also establishing quantitative baseline data on deep joint heating dynamics.
Although cadaveric limitations preclude thermoregulation and blood flow effects, the study provided the first direct invasive measurement of capsular and intra-articular temperature changes during Tecar therapy, validating the mechanistic precision of 448 kHz energy delivery in living patients.
