This article presents the clinical features of crystal arthropathy after knee replacement. The current literature on pseudogout and gout after both total and partial knee replacement is summarized. A case of bilateral pseudogout 8 years after initial total knee arthroplasty (TKA) is used to highlight the clinical characteristics and treatment options for this underrecognized condition. Presentation mimicked a late septic joint arthroplasty with sudden onset of pain and effusion. The patient was treated successfully with an arthrotomy, debridement, synovectomy, polyethylene insert exchange, oral steroids, and nonsteroidal anti-inflammatories. There are no other reported cases of bilateral pseudogout after bilateral TKA.
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Pseudogout and gout should be considered in the differential diagnosis of patients with acute pain after joint replacement.
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Infection and crystal arthropathy have very similar presentations after joint replacement and can often be confused for one another.
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A full infectious workup should be initiated in all patients with pain after arthroplasty even if crystal arthropathy is suspected.
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There are no large studies describing crystal arthropathy; however, the current literature available suggests that it is a true entity and can be treated well with a combination of medical and surgical management.
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The true prevalence of crystal arthropathy after joint replacement is still unknown.
Introduction
Acute onset of pain and swelling after a total knee arthroplasty (TKA) should prompt an immediate and thorough workup to rule out infection. Despite the importance of excluding infection, one must also consider the uncommon diagnosis of crystal arthropathy. Although rare, gout and pseudogout have similar presentations in the infected TKA and may mimic a prosthetic joint infection. Symptoms may include erythema, warmth, pain, and decreased range of motion, as well as constitutional symptoms such as fever and malaise. Both gout and pseudogout may be clinically indistinguishable from septic arthritis on physical examination as well as laboratory examination.
To date, the literature contains only a few published reports of unilateral gout or pseudogout after TKA. To the authors’ knowledge, this is the first published case of bilateral pseudogout after bilateral TKA.
Case report
The patient was a 70-year-old woman 8 years after bilateral TKA, with acute onset of bilateral knee pain for 1 day. The patient had been very happy and pain free with her total knees for the past 8 years, without any complaints. She had been walking without assistance and was exercising daily. The morning before presentation she woke up with severe bilateral knee pain and could not stand. The patient presented in a wheelchair and reported severe pain and inability to ambulate because of the pain. She had no recent history of infection and no prior constitutional complaints.
On examination on the day of presentation, the knees were erythematous with a moderate effusion. She had severe pain with limited range of motion; the range of motion was 30° to 90° bilaterally. Both knees were aspirated under sterile conditions and the aspirate was suspicious for infection. A thick, brownish, viscous fluid was aspirated from both knees. The white blood cell (WBC) count in the joint fluid aspirate of both knees was 64,200×10 9 /L and 89,500×10 9 /L, with 76% and 82% neutrophils. This aspirate did not initially demonstrate crystals on microscopic evaluation. The erythrocyte sedimentation rate (ESR) was 25mm/h and the C-reactive protein (CRP) was elevated at 13.4mg/L. The patient also had an elevated serum WBC of 12.3×10 9 /L. Radiographs demonstrated well-aligned bilateral TKAs without any sign of loosening or osteolysis ( Fig. 1 ).
After the aspiration yielded purulent-appearing fluid, and in light of the clinical presentation, the presumed diagnosis was bilateral prosthetic joint infections. The patient was immediately admitted to the hospital for urgent operative intervention. She underwent bilateral open arthrotomy, synovectomy, irrigation, and debridement, with exchange of the tibial polyethylene insert.
At the time of surgery the synovium was sent for frozen section. The gross appearance of the synovium was noted to be tan and gray in color. Multiple calcified papillary projections were noted on microscopic inspection. There was evidence of acute inflammation, with approximately 50 polymorphonuclear cells per high-powered field. Furthermore, there was hystiocyte infiltration and foreign-body giant-cell reactions were noted in the synovium. Calcium pyrophosphate crystals were seen in the synovium and the synovial fluid from the intraoperative specimen. The intraoperative joint fluid cell count and differential demonstrated greater than 97,000 WBCs and 97% neutrophils. The patient was started on vancomycin, 1 g intravenously every 12 hours postoperatively. However, multiple cultures from both knees, including tissue cultures, were negative for any bacterial growth and finalized after 5 days. Antibiotics were stopped on postoperative day 3. With these results and with consultation with infectious disease and rheumatology, the final diagnosis was determined to be bilateral pseudogout.
The patient was treated with prednisone, 20 mg daily for 3 days, then this was tapered over 5 days. She was also treated with colchicine, 0.6 mg daily. By the fourth postoperative day, her laboratory tests were normalizing. Her serum WBC count was 6.9×10 9 /L and her CRP had begun to trend down to 4.6mg/L. The ESR remained elevated at 33mm/h. On the 10th postoperative day she was discharged home on oral colchicine, 0.6 mg daily, to prevent any future pseudogout attacks.
The patient continued to be followed by her rheumatologist and returned to her usual activities. She is taking colchicine therapy, 0.6 mg daily, and has not had another acute exacerbation of pseudogout. At her 16-month follow-up visit the patient was doing very well and had resumed her usual activities. She was ambulating without assistance, and had range of motion from 0° to 100° on her right knee and 0° to 110° on her left knee ( Fig. 2 ).
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