Knee swollen after long time working on them, then side of knee bruised on thigh, then foot swelled and looks bruised, what happened?left leg

Overuse syndrome: You may have developed some inflammation and swelling form arthritis and an overuse syndrome from the work you did with pressure on your knees. The increased swelling can cause a pressure against your venous outflow and subsequent swelling in your lower leg too. I no resolution, get eval form Dr. to be assessed for definitive diagnosis. Good luck.

Ruptured Baker cyst : Possibly a ruptured Baker cyst. Please see Dr soon to confirm.