What Are The Uses And Side Effects Of Cortisone Injection?

Are cortisone shots perfectly safe, no matter what the age? My 98-year-old father had two cortisone shots one day (one in shoulder and one in knee) and the next day had weakness and tingling in one hand and difficulty walking. Took him to ER to be sure he had not suffered a stroke and CT scan showed no sign of stroke) Just a coincidence or could it have been some sort of reaction? I have not read that this type of reaction would be an ordinary side effect of cortisone.