Swollen/bruised knees, rashes, help!!

Okay so for the past month I’ve noticed I’ve been having a hard time walking. My body’s stiff, knees are insanely sore but here’s where it gets weirder, my knees and legs look bruised! I have not fallen, I’ve not hit my knees or been on my knees, I’ve not changed anything in my diet, laundry detergent has been the same as always and for the picture of me in the bath, my knees were like that before. I only got in the bath because the pain was so bad! It seems to progress worse during the day and typically ends up like this in the evening (swollen knees, bruised looking and rashes) what could cause this?! It just doesn’t make sense, my knees have looked bruised for a few weeks now and pains almost unbearable! The rash doesn’t really itch or anything either!