Will my cat be okay? what should i do.?

a few years ago, my cat max got hit by a car, and went under surgery a few times because his leg kept popping out. his leg has been fine for about 4 years, but hes been limping on his right leg. last night while trying to go to bed, max was laying on my quilt. so i moved the quilt from under him. he meowed and groaned 3 times. this morning i woke up and he was under my bed. when i got home from work, he was still there. i fed him some wet food and water, and he came out from under my bed. his right leg was lifted in the air while trying to walk, and he meowed a few times while sitting on it. hes been doing the same stuff he usually does, so i just wonder if his leg is sore, or if it popped out again.