What is a characteristic symptom of stage 1 CRPS?

In stage 1 of Complex Regional Pain Syndrome (CRPS), a hallmark characteristic is that the pain is typically unprovoked and can occur at rest. This pain often feels disproportionate to any initial injury and may be described as burning, aching, or throbbing. Unlike other stages that may exhibit additional physical changes such as muscle atrophy or joint immobility, the first stage primarily manifests intense pain and sensitivity.

While atrophy and physical changes may develop in later stages, they are not present at this initial stage. As for the frozen shoulder, this condition can result from disuse or pain in later stages but is not a characteristic symptom of stage 1 CRPS. Thus, the defining feature of stage 1 is indeed the persistent and unprovoked pain, making it the correct answer.