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Total knee arthroplasty (TKA) has been shown to be a successful and cost-effective procedure for decreasing pain and restoring function in patients with end-stage osteoarthritis.1–5 However, patient dissatisfaction has been reported to be as high as 50%,6 with residual pain being the most common factor contributing to dissatisfaction.3,7 Rates of pain between 9% and 14% have been reported at 10-year follow-up of TKA.1,2,6
Determining the causes of the pain is often a diagnostic challenge, and there are multiple potential etiologies for residual pain following TKA, such as low-grade infection, midflexion instability, and component malalignment with patellar maltracking.8 Less common causes of residual knee pain include crepitation and patellar clunk syndrome, patellofemoral symptoms, early aseptic loosening, hypersensitivity to component materials, and complex regional pain syndrome (CRPS).8 Complex regional pain syndrome can cause disabling pain, stiffness, and prolonged recovery, but it is often overlooked because available diagnostic modalities are not specific.8,9
Complex regional pain syndrome is a potential cause of persistent pain after TKA. A retrospective study of patients diagnosed with CRPS affecting the knee found TKA to be the second most common inciting event, behind arthroscopy.10 However, the condition following TKA is less well characterized.11 This article reviews the current literature regarding CRPS after TKA, explains the diagnosis, and discusses treatment algorithms.
Pathophysiology of Complex Regional Pain Syndrome
Complex regional pain syndrome is a chronic pain condition with autonomic and inflammatory features that affects limbs after injury.12 It is a complex neurological disease with a variable characterization, but CRPS mainly presents with spontaneous or stimulus-induced pain that is out of proportion to the initial injury, autonomic instability, motor and sensory dysfunction, trophic and ischemic changes, and prolonged recovery time.13–16
There are many historic synonyms for this condition, including reflex sympathetic dystrophy, Sudeck's atrophy, causalgia, algodystrophy, and algoneuro-dystrophy.17,18 However, the International Association for the Study of Pain consolidated the terms into CRPS to encompass the wide variety of disorders of previous terminologies and descriptions.18,19 Complex regional pain syndrome is further divided into type I and type II. Type I includes reflex sympathetic dystrophy and related conditions without nerve injury, whereas type II includes the development of causalgia following peripheral nerve damage.20 Despite simplified nomenclature, CRPS continues to be misdiagnosed due to the heterogeneity of patient presentations. This...