Arthritis is a term that refers to inflammation of the joints. Arthritis often results in joint pain
. Arthralgia refers to the term for muscle pain
. Muscle pain is a separate (albeit often related condition) that is medically known as a myalgia. Regardless, any of these condition, requires evaluation. Therefore, I would recommend that you discuss this with your primary care doctor
Pain is actually a complex sensation that requires evaluation. Determining the source of the pain is sometimes difficult, but certainly the first step. As you mention, the joint and the muscles are two common sources of pain -- but there are others. The nerves and blood vessels often also can contribute to pain. A complicating factor is that having any of these as the source of pain is not mutually exclusive -- for example people with knee arthritis often have to change the way they walk to accommodate the pain. This results in strain on the calf muscle -- so muscle pain results.
There are many causes of the pain you are experiencing -- and hearing the story more fully, examining the area, and potentially checking some blood tests or even getting images of the area maybe required. Knowing the source of pain is key as each have a different treatment. Talk to your doctor to assist in this evaluation. Good luck!