Thanks for posting your query.
Swelling of legs and knees is not a normal thing. It would be due to arthritis
or as a part of infections like septic or tubercular.
It would be of concern and you need to be evaluated by proper investigations like X-ray of concerned joints, Blood tests for infection and for antibodies
You can initially try with Analgesics and adequate rest and hot compresses.
I suggest you to consult a orthopedician if there is no relief.
Hope I have answered your query.
Wishing you good health.