SENSITIVE JOINTS. Great question with no scientific answer. Many patients with arthritis experience this. There is some research looking at how patients with osteoarthritis process pain. There seems to be more to the pain than just the bones rubbing against each other. There is research showing how the central nervous system (brain and spinal cord) are intimately involved in processing arthritis pain.
COLD JOINTS. It seems that the central nervous system (brain & spinal cord) is involved in processing arthritis pain. This may explain why many people with arthritis are sensitive to the cold. I find it interesting that duloxetine (cymbalta) has been fda approved to treat osteoarthritis pain. This drug works on the central nervous system to turn the volume down on osteoarthritis pain.
Exact cause unknown. Most all patients with arthritis feel better in drier and warmer climates. Perhaps this increases blood flow to the affected joints but the exact mechanism is unknown. Medicine is both and art and a science. We listen to our patients, but do not yet always have the scientific explanation.