I Fall Down 3weeks Ago On My Right Knee Immediately

I fall down 3weeks ago on my right knee immediately my joint was swallen with inability to move mri showed tibial tubrosity contusion with small fragments plus moderate effusion and anterior cruciate ligament sprain Clinically there is quadriceps muscle pull grade 3 my question how long it take to resolve because until now l have difficulty using stairs and still l have pain on full flexion