Overview
Complex regional pain syndrome (CRPS) of the knee, also known as reflex sympathetic dystrophy or causalgia, involves chronic pain, swelling, and functional impairment disproportionate to any precipitating injury. It often presents with sensory, motor, and trophic changes localized to the affected limb 6.Diagnosis
Clinical Criteria: Presence of pain disproportionate to injury, sensory or motor changes, edema, and skin color changes 6.
Imaging: MRI may be useful to rule out other causes like fabella syndrome or osteocartilaginous degeneration in the fabellofemoral joint 3.
Evaluation: Comprehensive history and physical examination are crucial; imaging should be guided by clinical suspicion rather than routine 2.Management
First-Line Treatments:
- Physical Therapy: Focus on restoring function and strength, particularly addressing imbalances like those seen in activities involving knee strain (e.g., dinghy sailing) 5.
- Sympathetic Blockades: May be considered for severe cases to reduce pain and improve function 6.
Adjunctive Treatments:
- Pharmacotherapy: Nonsteroidal anti-inflammatory drugs (NSAIDs) for pain management; caution with aspirin in heat due to potential adverse effects 7.
- Psychological Support: Cognitive-behavioral therapy can complement physical treatments 4 (Evidence: Moderate).Special Populations
Pediatrics: Use validated but shorter outcome measures like PROMIS to avoid patient fatigue; Pedi-IKDC remains a gold standard 1.
Elderly: Consider fabella syndrome or degenerative changes in the fabellofemoral joint as potential causes of knee pain 3.Key Recommendations
Conduct a thorough clinical evaluation before ordering imaging studies to ensure appropriate use of MRI in diagnosing knee pain 2 (Evidence: Moderate).
Utilize patient-reported outcome measures like PROMIS for pediatric patients to monitor progress efficiently without causing fatigue 1 (Evidence: Moderate).
Consider nonsurgical interventions such as physical therapy and NSAIDs for managing anterior knee pain, though evidence varies; individualized treatment plans are recommended 4 (Evidence: Weak).
Exercise caution with aspirin therapy in physically active older adults, especially in hot conditions, due to potential adverse effects 7 (Evidence: Expert opinion).References
1 Schafer KA, Minaie A, Nepple JJ. Outcome Metrics in Pediatric Sports Medicine: Do PROMIS Computer-adaptive Testing Metrics Correlate With Pedi-IKDC?. Journal of pediatric orthopedics 2020. link
2 Wylie JD, Crim JR, Working ZM, Schmidt RL, Burks RT. Physician provider type influences utilization and diagnostic utility of magnetic resonance imaging of the knee. The Journal of bone and joint surgery. American volume 2015. link
3 Ehara S. Potentially symptomatic fabella: MR imaging review. Japanese journal of radiology 2014. link
4 Collins NJ, Bisset LM, Crossley KM, Vicenzino B. Efficacy of nonsurgical interventions for anterior knee pain: systematic review and meta-analysis of randomized trials. Sports medicine (Auckland, N.Z.) 2012. link
5 Newton F. Dinghy sailing. The Practitioner 1989. link
6 Henry JH. Unusual cause of knee pain in the older adult. Orthopaedic review 1989. link
7 Fred HL. Reflections on a 100-mile run: effects of aspirin therapy. Medicine and science in sports and exercise 1980. link