My cats front leg is injured. No clue whats wrong.?

So my cat (Mikko) is a fat male, about 10 years old. He does not go outside much, especially in the winter. His left front leg has been bothering him. He will not place in down when he is not moving, and will limp when moving. Even when he is lying down, he tends to keep is paw up in the air to avoid touching it to the ground. I checked him out too see if there was any breaks but it doesn't seem to bother him when I touch it. I would like to see if its something serious or something I can fix before bringing him into the vets office. Any ideas on whats wrong?

(I know for sure its not a cat bite or an animal attack)