A 46-year-old nurse comes to the acute care clinic 3 weeks after injuring her left knee while transferring a patient. She felt a "twinge," but there was no immediate deformity or subsequent edema, and she was able to continue walking normally. Within 2 weeks, she developed intense pain around the left knee and could hardly walk or put any weight on the left leg. Placing clothing or sheets on the left knee produces abnormal discomfort and insomnia. She is prescribed naproxen and oxycodone. Over the next 2 months, the patient notes swelling around her left knee, an increased temperature, and more sweating of the left leg compared to the right. Sometimes the left leg has a mottled, bluish discoloration. Even on analgesics, exacerbation of her knee pain by flexion and extension causes her to limp. She also complains of poor sleep and constant fatigue. Which of the following is the most likely diagnosis?

Question

A 46-year-old nurse comes to the acute care clinic 3 weeks after injuring her left knee while transferring a patient.  She felt a "twinge," but there was no immediate deformity or subsequent edema, and she was able to continue walking normally.  Within 2 weeks, she developed intense pain around the left knee and could hardly walk or put any weight on the left leg.  Placing clothing or sheets on the left knee produces abnormal discomfort and insomnia.  She is prescribed naproxen and oxycodone.  Over the next 2 months, the patient notes swelling around her left knee, an increased temperature, and more sweating of the left leg compared to the right.  Sometimes the left leg has a mottled, bluish discoloration.  Even on analgesics, exacerbation of her knee pain by flexion and extension causes her to limp.  She also complains of poor sleep and constant fatigue.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

Explanation: This patient presents with knee pain, swelling, decreased range of motion, skin changes, and vasomotor changes after a recent injury consistent with complex regional pain syndrome (CRPS). This syndrome was previously known as reflex sympathetic dystrophy, algodystrophy, causalgia, Sudeck atrophy, transient osteoporosis, and acute atrophy of bone. Usually occurring after an injury, CRPS presents with pain out of proportion to the injury, temperature change, edema, and abnormal skin color. Type I CRPS (90% of CRPS cases) occurs without a definable nerve lesion, while type II occurs with a definable nerve lesion. The pathogenesis is likely due to an injury causing increased sensitivity to sympathetic nerves, an abnormal response to and sensation of pain, and increased neuropeptide release causing burning pain to light touch (allodynia). Typically, CRPS occurs in 3 stages. Stage 1 includes burning pain, edema, and vasomotor changes in a limb after injury. Stage 2 includes progression of edema, skin thickening, and muscle wasting. Stage 3 is the most severe and includes limited range of motion and bone demineralization on x-ray. Diagnosis can be confirmed by either autonomic testing that measures increased resting sweat output or magnetic resonance imaging that looks for the above changes. The treatment for CRPS is regional sympathetic nerve block or intravenous regional anesthesia. This patient appears to have Stage 3 disease and would benefit from a local nerve block. (Choice A) Anterior cruciate ligament injury typically occurs due to a contact injury or sudden deceleration/acceleration injury. It presents with initial swelling that resolves, allowing the patient to bear weight while having an unstable joint. There are usually no skin changes or sensory symptoms. (Choice C) Deep vein thrombosis might cause unilateral leg swelling with pain and erythema but not usually regional knee pain with difficulty in weight bearing. (Choice D) Peripheral neuropathy can be associated with allodynia but is typically associated with sensory changes in one limb rather than one joint with skin changes. (Choice E) Raynaud syndrome causes skin changes with exposure to cold temperatures, but the changes are more commonly seen in the hands and toes than the knee. Educational objective: Complex regional pain syndrome should be suspected in patients with recent joint injury who present with local burning pain, edema, skin changes, and decreased range of motion. References: Reflex sympathetic dystrophy of the knee. Causes, diagnosis, and treatment. (http://www.ncbi.nlm.nih.gov/pubmed/8600729) Signs and symptoms of reflex sympathetic dystrophy: prospective study of 829 patients. (http://www.ncbi.nlm.nih.gov/pubmed/8105263)

A 46-Year-Old Nurse Comes to the Acute Care Clinic 3