Stiffness in back joints, knee joints.

Will need rheumatoid treatment. If your ortho not giving medicines  then consult rheumatologist.

Physiotherapy treatment for few days to release stiffness of knee then start quadriceps exercises. Tk calcium supplement.

Quadriceps strengthening exercises- Quad Clenches: Lie flat on your back or sit upright on a chair with leg kept horizontally on another surface. Now, tighten the muscle on the front of the thigh by pushing your knee down. You should feel your thigh muscles clench, Hold for 3 secs. Repeat 10 times twice a day. Short Arcs: Lie flat on your back or sit upright with your leg placed horizontally on a flat surface like a chair or bed. Place a rolled up towel under the knee. Pull your toes towards you and clench you thigh muscles. Slowly lift your foot up off the bed until your knee is straight (keep your knee resting on the towel). Hold for 3 secs and slowly lower them on the chair. Repeat 10 times twice a day. Straight Leg Raise: Lie flat on your back. One leg and knee will be straight and other leg should be bent. Pull your toes towards you and tighten/clench the muscle on the front of the thigh, locking your knee straight. Lift your foot up in the air, about 6 inches off the bed. Hold for 3 secs and slowly lower the leg. The knee must remain straight the whole time you are doing this exercise.

As your orthopaedic doctor suggested you need to visit a  rehumatologist.He will suggest medication for pains along with medication start sound exercises regularly for all the joints this will keep the joints preserved and healthy

Consult rheumatologist along with medicine take physiotherapy treatment, learn proper exercise to strengthen muscles and do it regularly.