You are suffering from chronic, dull aching pain coming from a limb or tissues from your spine. This type of pain is referred to as somatic. That is to say, the pain is coming from tissues other than nerves that have been injured from trauma, inflammation or infection. It can also come from changes occurring after surgery, such as spine surgery or joint replacement. Even though this pain is NOT coming from damaged or injured nerves, the transmission of the pain impulses to the brain has to be conducted through nerves. There are three basic types of nerves: nerves that make us perceive pain (nociceptive nerves); those that make us feel and touch (sensory or somatic nerves); and those that make us move (motor nerves). The nerves to our limbs, then, are a collection of all three types of nerves. All these different types of nerves are intermingled while serving the limbs, but when they come to the spinal cord, they need to be organized into their respective types before they enter the spinal cord on their journey to the brain. This organization is done at the nerve root immediately outside the spinal canal in a part of the nerve root referred to as the spinal ganglion.
This is much like cable TV. Millions of viewers from all over the USA communicate through wires (nerves) to the cable network transmitter. Here, all these wires come together and are organized to location; that is, the top of the cable contain all the wires from Chicago, the middle of the cable serves New York and all wires from St Louis are on the bottom. If the cable were to break, then all of Chicago would be without cable service, whereas maybe only some in New York and none of St. Louis would be out of service. The same is true with our bodies. It is in this ganglion that all the nerves are positioned strategically so that the pain nerves lie the back part of the ganglion (dorsal), the sensory nerves in the middle and the motor nerves on the front (ventral) part.