I am practicing on these data I have and I want to apply a statistical test.

I want to compare 2 treatments: evolution and incidence of a certain disease after treatment.

There were 3 groups taken into study: treated with A (n=78), treated with B (n=65) and C=control group, untreated (n=72).

I evaluated them initially, 6 months and 12 months after the initiation of treatment. Each subject received score 0, 1 or 2 at these time points.

Since the data are categorical, I am thinking of applying chi-square test, but I am not quite sure about the steps I have to follow.

Should I calculate expected value (and how?), the distribution of the data (?). Could you suggest some steps (mean, standard deviation)? Thank you!