My knees have started turning red and itchy and the tops of my feet in a red like from big toe to ankle- symmetrical, what's going on?

Nothing beats exam: For a proper diagnosis, it really is necessary to be seen; nothing beats a physical exam and obtaining a full history. In the case you describe, it really is necessary; red rashes in the lower extremities can be a sign of infection (e.g. Cellulitis, which is serious and needs treatment immediately), contact dermatitis (such as poison ivy), eczema, psoriasis, and a variety of other problems.

Dermatologist: These symptoms may represent a dermatological condition. I recommend that you see your primary care physician or a dermatologist for further evaluation and treatment (if needed).