Hi, I Walk Everyday For At Least 1hr As I

Hi, i walk everyday for at least 1hr as i have a collie dog! over the last fews weeks i have had sciatica like pain from right buttock, back of legs and down front of leg and foot which causes me pain after walking for more than 20 minutes, my knee swell up quite badly every few months. I also have a 3 year old granddaughter whom i dace a lot with and also lift her up a lot!! I have tries various different pain relief which is not very effective including 50mg either once or twice a day. Just worried about bone cancer.I am 60yrs old and normally very healthy, i am also a nurse so not over analyzing the situation. Would appreciate your advise
Thank you Kathleen.