Had arthroscopic knee surgery 4 weeks ago and since Friday the ankle is swollen why and should the doctor be contacted?

First off I'm not a doctor. I had knee surgery and at about the same time as you my leg swole up from my knee down. I was watching football with my in-laws and they noticed the size of my leg. I took my shoe off my ankle, foot, and toes were swollen. I had my doctor paged and he said to get admitted into the hospital immediately because I had a blood clot. I had an aquantince have a surgery and had a blood clot after mine. He ended up dying. Just be careful. Best of luck!