What causes complex regional pain syndrome (CRPS)?
We don’t yet know exactly what causes complex regional pain syndrome (CRPS) but a fracture or other injury sometimes seems to act as a trigger. Symptoms of CRPS start within a month of the injury.
It's though that the nerves of the affected limb are much more sensitive than normal and that pain pathways between the affected limb and the brain may change so that pain continues long after the original injury has healed. The pain and other symptoms also affect a wider area than the original injury.
More rarely, CRPS can occur after other problems such as a stroke or multiple operations to a limb. In other cases (about 1 in 10) it develops without any obvious trigger factor.