For reducing patient pain during treatment of patellar tendonitis, which solution is most appropriate for use with iontophoresis?

Lidocaine is an appropriate choice for iontophoresis in the treatment of patellar tendonitis because it is a local anesthetic that provides pain relief. When delivered through iontophoresis, lidocaine can penetrate the skin and create a temporary numbing effect in the localized area of treatment. This is particularly beneficial in managing pain associated with conditions like patellar tendonitis, as it helps improve patient comfort during physical therapy interventions.

Other solutions mentioned in the options serve different therapeutic purposes. Acetic acid is typically used for conditions related to calcific deposits or tissue calcification; its role in pain reduction is not as direct as that of lidocaine. Sodium chloride is often used in acute management situations for hydrating tissues or in saline solutions but does not have analgesic properties. Zinc oxide is sometimes applied for its skin protective and healing properties but does not effectively alleviate pain in the way lidocaine does. Therefore, when specifically targeting pain reduction with iontophoresis, lidocaine is the most effective and appropriate choice.