Medicine is not a perfect science. All medical care is associated with unknown, and perhaps unknowable, risks. The physician must tell the patient of the known risks of treatment, but this is not a guarantee that other problems cannot occur. Patients may assume these unknown risks if three conditions are met:

1. The risk is unknown (or of such a low probability that it is not known to be causally related to the procedure).

2. The patient is informed that the disclosed risks are not the only possible risks.

3. The medical rationale for the treatment is sound.

Condition 3 means that a patient cannot assume the risks of a negligently recommended treatment, an important issue with marginal treatments and vanity surgery. A patient who suffers a complication from an improper treatment may always sue the physician who recommended the treatment. A detailed consent form, listing all the risks of a treatment, is no protection if the treatment is unnecessary. If a patient can prove that a treatment was unnecessary or contraindicated, then the consent to risks of the treatment becomes ineffective.