My vet says my cat has rickets, but he can jump and run. Is this normal?

I think perhaps you're asking about Rickets Disease. Rickets is a disease of young, growing animals that causes soft and deformed bones. It is commonly caused by insufficient phosphorus or vitamin D in the diet. More rarely, calcium deficiencies are to blame. As in most diets causing defective bone formation, the cause is typically an imbalance in the ratio of calcium to phosphorus. Animals fed all-meat diets are commonly affected. It's very important to get him on a well balanced diet - I recommend Hills, Royal Canin, or Purina (although I don't know if they are available in Turkey) - to try to correct the issue. Prognosis is generally good, after an appropriate diet is started, unless he's started to have broken bones or his growth plates are affected. I hope that helps!