Therapeutic Modalities
Thermal agents
Cryotherapy reduces blood flow, edema, spasm, and pain; typical application 10–20 minutes with a barrier. Thermotherapy increases blood flow and tissue extensibility and is used before stretching. Both depend on intact sensation and circulation - the single most tested safety screen.
Electrical currents
- TENS: conventional high-frequency (roughly 80–150 Hz, short pulse) uses the gait-control mechanism for rapid, short-lived relief; acupuncture-like low-frequency (2–4 Hz) is slower in onset and longer lasting.
- NMES: used for muscle re-education and strengthening; contraction quality depends on adequate amplitude and patient tolerance.
- Iontophoresis: direct current drives charged drug ions - dexamethasone and acetic acid are delivered from the negative pole; lidocaine and hydrocortisone from the positive pole. Polarity errors are a classic distractor.
Ultrasound
Depth is frequency-dependent: 3 MHz is superficial (about 1–2 cm); 1 MHz is deep (about 3–5 cm). Continuous (100%) duty cycle is thermal; pulsed (typically 20%) is nonthermal. Higher intensities are used for thermal effects over large muscle bellies, lower for acute or bony areas.
Traps
Mixing up duty cycle and intent, confusing phonophoresis (ultrasound-driven) with iontophoresis (current-driven), and forgetting that modalities are adjuncts to, not substitutes for, exercise and load management.
Rule of thumb
Before any thermal or electrical agent, run the same four-item screen: sensation, circulation/skin integrity, cognition/communication, and implanted devices.