What constitutes a probable risk and a special risk?

At pp. 659-60 of Hopp v. Lepp, Laskin C.J. described what could constitute probable risks, and special or unusual risks: ... Probable risks, which must be disclosed, have been contrasted with mere possibilities (as, for example, risks involved in any operation), but this dichotomy cannot be absolute because it ought to take note of whether a risk is or is not quite remote, and here the gravity of the consequences, if a risk should materialize, must be brought into account; for example, the risk of death, even if a mere possibility, as contrasted with some residual stiffness of a member of the body. ... ... Special or unusual risks may, however, go beyond those that are probable in respect of the surgery or therapy involved in a particular case and could relate to serious consequences in the particular instance even if the risk be a mere possibility. ...