I Started Exercising Harder About 3 Weeks. My Knees Started

I started exercising harder about 3 weeks. My knees started hurting me so bad. I could hardly get off the floor and stand up. The on call doctor gave me Mobic for ten days. She told me to wear a knee brace for two weeks and to take it easy. To only do upper body exercises. I am in the hospital for something else, the nurse practicenor told me to take ultram for pain since I am taking 900 mg of Lithium. I have been on ultram for almost a week. I still have no relief. Can you suggest a orthopedic doctor in the Houston area.

Thank you