Standing on my right knee causes pain that of burning sensation. It lasts secs once I get off knee. No swelling. Fallen on them 10yrs. Nerve damage?

Sounds like you have. Arthritis, or a meniscal tear. The fall might be responsible for the arthritis, but i think its the daily activities with subtle injuries in a susceptible person resulting in a meniscal tear. Its not a nerve issue. See an orthopod and I am sure he'll help you. In the meantime, use a cane for support, as I have seen too many people falling ; making it worse. Good luck.