A physical therapist prepares to administer iontophoresis over the anterior surface of a patient's knee while keeping the current density low. Which parameter would BEST accomplish this objective?

To achieve a low current density during iontophoresis, it’s essential to manipulate the current amplitude in relation to the surface area of the electrode used. Current density is calculated by dividing the current amplitude by the electrode area, expressed in milliamperes per square centimeter (mA/cm²).

When considering the options, the first choice provides a current amplitude of 4 mA and an electrode area of 12 cm². This setup results in a current density of approximately 0.33 mA/cm², which is relatively low. A lower current density is beneficial as it reduces the risk of skin irritation and discomfort during treatment.

In contrast, other options, such as those with a smaller electrode area or higher current amplitudes, lead to a higher current density, which may increase the likelihood of adverse effects like skin burns or discomfort. Therefore, the first option effectively balances the current amplitude with the electrode size to maintain a low current density during the iontophoresis treatment. This choice aligns with the objective of ensuring patient comfort and safety while maximizing the efficacy of the modality.