I just joined running in 10/2016,in 2017 i was on and off de road,2018 am committed as am preparing for comrades marathon 2018,evrytym my feet r burning nd sometimes i experience knee pain?

Multiple causes: There are multiple etiologies that can cause these problems. Long distance running can cause damage if you have structural deformities -flat feet, leg length discrepancies, scoliosis, or physical deformities such as osteoarthritis, and back problems. Burning feet involves nerve irritation and knee pain can be arthritis. Go see a sports orthopedist to evaluate.