The brain is constantly changing through a process called neuroplasticity. When you have an injury it sends signals of pain to the brain. Because of injury or pain you change the way you move. This can cause changes in the sensorimotor portions of the brain. These changes can persist beyond the initial injury repair and can disrupt sensorimotor re-integration (the healing process of the nerve patterns). This may explain why you may limp even after a leg injury has healed or why you have chronic pain from an old injury that healed years ago. Because of this process joint dysfunction/subluxations can contribute to the chronicity of injuries.
Medically these conditions are called allodynia or hyperalgesia. These are when the brain is reporting the wrong feedback to the body (pain with light touch, or tingling sensation when nothing is really going on). You see your brain has a sense that you may not be aware of. Beyond your touch, taste, smell, hearing and sight you have a sense is called proprioception. It’s the ability of your body to sense where any part of it is in space even without the other senses. This sense comes from all the afferent signals that your muscle spindle fibers, Golgi tendon organs, etc… send to the brain. Vertebral subluxation is a state of altered afferent input which can lead to maladaptive central plastic changes that over time can lead to further dysfunction. In other words interference in the path of communication is like playing that game telephone, and the signal that the body sends is not what the brain gets or visa versa. This interference does affect all communication that comes through the area. So, if you have a bad knee and a bad back the brain may not know how the knee is doing even after it has healed because the back problem interfered. Because these subluxations can contribute to these conditions fixing subluxations can also contribute to resolving them.
Chiropractic care improves the health and function of the spine, so that it can accurately perceive what is going on and respond appropriately which in turn helps clear up the communication between your brain, the body and the environment. When the communication lines are open for a long enough period of time then the chronic pain patterns have a chance to resolve.
Additional Research on the topic: