Electrotherapy and Physical Modalities
What you must understand
Know the physics and physiological effects of common modalities: ultrasound (thermal and non-thermal, cavitation, frequency and depth), transcutaneous electrical nerve stimulation (gate control and endogenous opioid mechanisms), interferential therapy, neuromuscular electrical stimulation, laser, shortwave diathermy, cryotherapy, and thermotherapy. Understand dosage parameters (frequency, intensity, duration, duty cycle) and contraindications such as malignancy over the area, pacemakers, pregnancy over the abdomen, impaired sensation, and metal implants for certain modalities.
Traps in questions
- Applying ultrasound over the spine in a pregnant patient or over a pacemaker.
- Using thermal modalities on a patient with impaired sensation or acute inflammation.
- Confusing transcutaneous electrical nerve stimulation (sensory, pain relief) with neuromuscular electrical stimulation (motor, muscle contraction).
- Forgetting that cryotherapy reduces oedema and pain but should be time-limited.
Rule of thumb
Modalities are adjuncts, never the primary plan. Ask: does the patient have intact sensation, a pacemaker, malignancy, or pregnancy? If yes to any, choose a safer modality or none. Match ultrasound frequency to depth: higher frequency for superficial tissue, lower frequency for deeper tissue.
Worked example
A patient with a pacemaker and shoulder pain asks about electrical stimulation. Best answer: avoid electrical stimulation over the chest and use exercise and manual therapy instead.