Regular arthritis is less common in younger people (but still possible), but Rheumatoid Arthritis commonly onsets at an earlier age. I do not think you have arthritis or RA, though, and I don’t want you to worry about it (although seeing a doctor is a good idea). I think you’re having growing pains and soreness from being active in volleyball. I was sore often at that age too.
Do get checked out just in case, though, dear.
You don’t have any open wounds or anything that might invite infection, do you? My first symptom of sepsis was extreme body pain, especially in my knees. But I had a PICC (peripherally inserted central catheter) at the time.