It can be caused by a peripheral nerve injury (type 2) but often is not (type 1)
Clinical presentation
Charcteristics are variable but include constant burning or throbbing, sensitivity to stimuli not normally painful (allodynia) including cold or light touch, chronic swelling, stiffness, painful movement and skin colour changes
Management
Management is difficult and requires specialist pain services
Pharmacological agents including analgesics, antidepressants (amitriptyline), anticonvulsants (gabapentin) and steroids may help
TENS machines, physiotherapy, lidocaine patches and sympathetic nerve blocking injections may also help