Electrotherapy, Physical Agents and Modalities
Modalities and their rationale
Know the physical principles and evidence base for each modality. Electrotherapy includes TENS, NMES, interferential current, and therapeutic ultrasound. TENS modulates pain via the gate-control mechanism (high frequency, conventional) or endorphin release (low frequency, acupuncture-like). NMES recruits muscle for strengthening or re-education. Ultrasound uses mechanical vibration for thermal and non-thermal effects; use low intensity for acute, higher for chronic.
Thermal agents: superficial heat (hot packs, paraffin) increases blood flow and extensibility; cold (ice, cryotherapy) reduces pain, oedema and spasticity. Know the contraindications: heat over acute inflammation, impaired sensation, malignancy; cold in Raynaud's, cold hypersensitivity, impaired circulation.
Safety and evidence
Always check skin integrity, sensation, and the presence of metal implants or pacemakers (electrotherapy contraindication in some cases). Document parameters: frequency, intensity, duration, and patient response.
Traps
Questions test whether you know that ultrasound is not a substitute for exercise, and that TENS is for symptom relief, not tissue healing. A common trap is applying heat to an acute injury. Another is using electrotherapy over the thorax in a patient with a pacemaker.
Rule of thumb
Before any modality, ask: what is the intended effect (thermal, analgesic, neuromuscular), is it safe for this patient, and is there evidence it adds value beyond exercise? If the answer to the last is no, do not use it.