Specific nerves growing in the joint might be important in knee osteoarthritis pain

What is it about?

Knee osteoarthritis (OA) is a common cause of pain and disability and pain is the most common reason sufferers seek medical help. When the pain becomes extremely bad, knee replacements are the last option. Our earlier research has found that, in OA, changes within the bone can lead to nerves growing into the cartilage. These nerves might be a cause of joint pain in people with OA. A molecule called nerve growth factor is known to be important in causing knee OA pain. We looked for nerves that might feel pain and were growing towards or into the cartilage. We compared people with OA and painful knees who were having a joint replacement, with OA that was not painful. Our aim was to see if nerve growth factor was linked to painful knee OA. We compared 2 groups of people with different levels of knee pain. (1) OA and having a knee replacement; very painful. (2) OA in knees; but not known to have bad knee pain. Group (1) were recruited to the study in a knee OA clinic. Group (2) were taken from people who had died and their tissues were donated by relatives. The 2 groups were matched to have very similar OA in the cartilage of the knee. However, we found that nerve growth factor was more common in painful knee OA samples. It was commonly found in tissues that were growing into the cartilage.

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Why is it important?

This study shows that future research might usefully look into nerve growth factor and what is does in the joints. It gives us more clues about what might be causing pain in the knees, and how we might be able to suppress the pain (even if we don’t get rid of the knee OA).