complex regional pain syndrome (CRPS)
/ CRPS, 'see-arr-pee-ess' /
Imagine spraining a wrist or breaking a small bone, the kind of injury that should heal in a few weeks, but instead the pain not only stays, it grows out of all proportion, and the limb starts to look and behave strangely. This bewildering condition is complex regional pain syndrome (CRPS), one of the most dramatic examples of pain becoming a disease of the nervous system in its own right.
CRPS usually follows an injury, often a surprisingly minor one, to an arm or leg. The pain is far worse and lasts far longer than the original injury can explain, and it is typically burning, with severe allodynia (even a light breeze or a bedsheet is agony). Along with the pain, the affected limb shows changes the person cannot control: it may swing between hot and cold or red and pale, swell, sweat abnormally, grow extra or coarse hair, develop shiny or mottled skin and brittle nails, and become stiff, weak, and difficult to move. The brain's body map of the limb can even become distorted, so it feels foreign or the wrong size. The exact mechanisms are still being worked out, but it clearly involves an over-reactive nervous system and inflammation rather than ongoing tissue damage.
CRPS is the reason early, active, gentle rehabilitation matters so much, because the worst thing to do is to protect and immobilise the limb out of fear, which feeds disuse, stiffness, and the fear-avoidance cycle. Treatment leans on keeping the limb moving and used despite the pain, desensitisation, techniques such as mirror therapy and graded motor imagery that retrain the brain's map, pain-modifying medicines, and strong psychological support. Outcomes vary widely; many improve, especially with early treatment, but some are left with lasting disability, and there is no simple cure.
Weeks after a minor wrist fracture has healed, a woman's hand is still burning, swollen, and so sensitive that the touch of a sleeve is unbearable; the skin is shiny and the colour keeps changing. Rather than resting it, her therapist gently desensitises the hand and starts mirror therapy to retrain the brain's map of the limb.
In CRPS, protecting and resting the limb usually makes it worse; gentle, active use is the counterintuitive key.
The instinct to rest and shield a CRPS limb is exactly wrong; disuse worsens it. CRPS is real, poorly understood, and has no simple cure, but early active movement gives the best chance of improvement.