Reflex Sympathetic Dystrophy (RSD) is a chronic pain condition typically affecting a limb following an injury. It is characterized by pain disproportionate to the initial injury’s severity, accompanied by changes in the skin, nerves, muscles, and blood vessels. Modern medicine has largely replaced RSD with Complex Regional Pain Syndrome (CRPS) to reflect a broader understanding of the disorder. CRPS is classified into Type I (formerly RSD) and Type II, but the historical three-stage model remains a useful way to describe the traditional sequence of symptoms over time.
Stage I: Acute Symptoms
This initial phase typically lasts between one and three months after symptom onset. Pain is severe and burning, remaining disproportionate to the original trauma. This pain is frequently accompanied by allodynia, where a non-painful stimulus causes excruciating discomfort.
Inflammatory signs dominate this stage, including significant swelling in the affected limb, which can be puffy and tender. Marked vasomotor instability causes changes to skin temperature and color. The limb often appears red, blotchy, or mottled, and feels warm due to increased blood flow. Excessive sweating (hyperhidrosis) is also a common autonomic symptom.
Hair and nails may exhibit rapid growth. Early joint stiffness may begin to develop, making movement difficult. If the process is not halted, the condition typically progresses to the next, more chronic phase.
Stage II: Dystrophic Changes
This phase represents a transition from acute inflammation to more structural changes, typically lasting three to six months or longer. The swelling becomes more fixed, losing its pitting quality.
Pain remains severe, but the limb’s appearance shifts dramatically. The skin temperature often becomes noticeably cooler compared to the unaffected side. Color changes from red to a pale, mottled, or bluish hue, indicating poorer circulation. The skin may start to thicken, and the underlying tissue can become tougher (fibrosis).
Trophic changes become pronounced. Hair growth slows down, and the nails may become brittle, grooved, or prone to cracking. Joint stiffness worsens considerably, leading to a limited range of motion. Demineralization of the underlying bone (disuse osteoporosis) becomes visible on X-rays.
Stage III: Atrophic State
This state can develop approximately one year after symptom onset and may become permanent. It is characterized by irreversible tissue damage and significant functional impairment. The affected limb shows significant muscle wasting (atrophy) due to disuse and chronic nerve changes.
The skin appears pale, dry, thin, and shiny, often stretched tightly over the underlying structures. Severe contractures develop as muscles and tendons shorten, causing the joints to become fixed and virtually unusable. This can result in a fixed posture, such as a claw hand or a foot pointing downward.
Although pain may occasionally lessen, it often remains severe and unyielding, involving the entire limb. Functional loss is substantial, with pronounced changes to the skin and bone.
Understanding CRPS Progression in Modern Medicine
While the three-stage model provides a clear, descriptive timeline, contemporary medical understanding views it as historical rather than strictly predictive. CRPS does not follow this linear path in all patients. Many individuals may remain in the symptoms of Stage I or Stage II indefinitely, and some may never progress to the atrophic state.
Clinical research shows there is no consistent relationship between the disease duration and the presence of stage-specific features. For instance, a patient with long-standing CRPS might still exhibit acute warmth and swelling, or a patient with recent onset may already show atrophic changes. The current approach focuses on classifying CRPS based on the current symptom profile and functional impairments. Early diagnosis and prompt intervention are important because treatment outcomes are generally better when therapy begins during the acute phase.