is this legal?

My SO was hired by a temp agency, and was working at the job for 2 months(after 3 months the business actually hires you on) about 2.5 weeks ago he got injured, and it has left him unable to work because of the tendintis, but the company isnt covering the medical, missed hours(income), and is filling the position because they fired him over it. hes provided the company with doctors notes, and proof its work related.