Is it permissible to take a loan from the bank for the need of foot treatment?

It is not permissible to borrow with interest (riba) except in a state of extreme necessity, which is when it is highly probable that the illness will worsen to the point of perishing, or that its hardship will become unbearable. This is only after exhausting all permissible alternatives, due to the severe warning against riba and its eradication of blessings.