(Concern) Knee pain

I am someone who doesn't do any special exercise and only focuses on walking regularly.

It's not even power walking or anything like that; I just walk whenever I have time, usually walking to a meeting place about an hour away.

It usually takes about an hour and a half on foot to get to my mom's place, which is about 4 kilometers away, so I walked there and back as I normally do.

On the way back, suddenly around the middle, my right knee started to hurt slightly, and then pain spread to the back of my right knee and calf, to the point where I couldn't walk due to the pain.

I barely managed to walk home that day, and I was sick for two days, so I thought it was just because I walked slowly and rested, and then the pain disappeared.

Since that day, I occasionally experience the same pain, and I wondered why that is. It seems that the pain occurs when I carry heavy luggage.

I have had some back problems before, but is it possible that knee pain could cause strain on the lower back?

Is it possible for it to develop on only one side as well?

I'm worried whether this is a knee joint problem or a back issue.

Is there anyone who knows why I have symptoms like mine or what might be causing them?

Should I visit neurosurgery or orthopedics if I go to the hospital?