Which of the following scenarios indicates a possible CRPS diagnosis involving persistent pain and sympathetic changes?

The scenario that suggests a possible diagnosis of Complex Regional Pain Syndrome (CRPS) is the occurrence of pain following back surgery accompanied by symptoms of discoloration. CRPS is characterized by persistent pain that usually follows an injury or surgery and is often accompanied by various sympathetic changes, including alterations in skin color, temperature, and swelling in the affected area.

In this context, the presence of pain along with discoloration following a surgical procedure highlights the potential for CRPS, as the condition typically arises after an injury that leads to significant changes in nerve function and the pain response. These sympathetic changes provide crucial clues indicating the nervous system's abnormal response, which is a hallmark of CRPS.

In contrast, the other scenarios do not exhibit the complex presentation associated with CRPS. A minor injury like a skinned knee is unlikely to produce the persistence and severity of symptoms characteristic of CRPS, while pain after an ankle sprain usually resolves with time and is not generally linked to the same underlying dysfunction of the sympathetic nervous system. Pain without a history of trauma lacks the necessary trigger that is often noted in CRPS cases, further supporting why the selected scenario is the most indicative of this specific pain syndrome.