Can Lyme Disease Cause Knee Swelling After Knee Replacement?

Lyme arthritis commonly affects the knee
Diagnosing swelling around a replaced knee can be difficult
Symptoms resolved following 90 days of oral doxycycline

Can Lyme disease cause knee swelling after knee replacement? Lyme arthritis can cause substantial knee swelling, pain, warmth, and difficulty walking. In a rare case, a man with a previous total knee arthroplasty developed Lyme arthritis involving the replaced knee, and his symptoms resolved following 90 days of oral doxycycline.

In their article, “Medically Managed Lyme Periprosthetic Joint Infection: A Case Report,” Saar and Fairbanks describe a patient with acute Lyme arthritis complicated by a previous total knee arthroplasty.¹

Lyme disease caused swelling in a replaced knee

A 68-year-old man living in southwestern Virginia presented to a medical clinic with five days of swelling above the kneecap, pain, warmth, and mild redness of his left knee.

“He noted pain with passive flexion and extension of the knee, as well as a noticeable limp,” the authors wrote.¹

The man denied fever, chills, night sweats, unintended weight loss, recent trauma, and open wounds. He was physically active and had not experienced previous problems with the replaced knee.

Twelve years earlier, he had undergone a total knee arthroplasty for degenerative joint disease. The absence of recent trauma and the presence of a prosthetic joint raised concerns about the cause of the new knee swelling.

Joint fluid tested positive for Borrelia DNA

During the initial evaluation, 65 cc of yellow, turbid synovial fluid was removed from the knee. The synovial fluid contained 14,760 white blood cells per mm³, of which 90% were neutrophils.

No crystals were found. Routine bacterial cultures showed no growth, and Gram staining showed no organisms. However, a qualitative polymerase chain reaction (PCR) test detected Borrelia DNA in the synovial fluid.

Twelve days after the initial presentation, an orthopedic specialist aspirated the knee again, removing 23 cc of synovial fluid. Repeat bacterial cultures, Gram staining, and crystal testing were negative. Synovial fluid PCR again detected Borrelia DNA.

Knee pain and swelling resolved after doxycycline

The patient began doxycycline 100 mg twice daily. After 30 days, no knee effusion was found on examination, although he had signs of pes anserine bursitis. His doxycycline was continued for another 30 days.

After a cumulative 60 days of treatment, the patient reported trace swelling at night that resolved by morning. No effusion was found on examination, and doxycycline was continued for another 30 days.

“Upon completion of 90 days of doxycycline therapy, the patient returned for further evaluation, reporting the cessation of transient swelling and the absence of pain,” the authors wrote.¹

Two months after discontinuing antibiotics, the patient continued to report no pain, swelling, or limitation of his activities. No knee effusion was found on examination.

However, this report describes the outcome of only one patient. The authors also identified the lack of long-term follow-up as a limitation. The case does not establish that 90 days of oral doxycycline or nonsurgical treatment is appropriate for every patient with Lyme arthritis involving a prosthetic joint.

Treating Lyme arthritis around a knee replacement

Lyme disease involving a prosthetic knee is exceptionally rare. As of October 2023, the authors identified only five previously reported cases of Lyme periprosthetic joint infection in the medical literature.¹

Four of those patients were treated successfully with surgery and antibiotics. One patient was treated successfully with intravenous and oral antibiotics without surgery.

Because so few cases have been reported, there are no treatment guidelines specifically addressing Lyme arthritis involving a prosthetic joint.

“This has left physicians trying to blend the treatment guidelines for Lyme arthritis, which is medically managed with antibiotics, and PJIs, which involve invasive surgical procedures,” the authors wrote.¹

Ordinary bacterial periprosthetic joint infections can threaten the function of the joint and may require urgent surgery. Therefore, swelling, warmth, or pain around a replaced knee should not automatically be attributed to Lyme disease.

Diagnosing Lyme arthritis in a swollen knee

Lyme arthritis often causes intermittent swelling in one or a few large joints, particularly the knee. Constitutional symptoms such as fever may be absent.

The authors recommended considering Lyme arthritis when a patient presents with an atraumatic knee effusion, especially in a region where Lyme disease is prevalent.

Testing may include Lyme antibody testing and, in selected patients, PCR testing of synovial fluid. Synovial fluid PCR can provide useful supporting evidence, but it should not be considered a stand-alone test.

Borrelia DNA may remain detectable after treatment and does not necessarily prove that viable bacteria remain in the joint. PCR results must be interpreted alongside the patient’s symptoms, Lyme antibody results, synovial fluid findings, bacterial cultures, and clinical history.

What the case report authors concluded

• Lyme arthritis should be considered in patients with an unexplained, atraumatic knee effusion, particularly in areas where Lyme disease is prevalent.
• Synovial fluid PCR testing may be useful when evaluating possible Lyme arthritis involving a prosthetic knee.
• Medical management may be an option for selected patients with new-onset symptoms, potentially avoiding the risks of surgery.
• The effectiveness of nonsurgical treatment in patients with more prolonged presentations remains unknown.
• Longer follow-up is needed to evaluate the risk of recurrent symptoms and the lasting effects on the prosthetic joint.

Frequently Asked Questions

Can Lyme disease cause knee pain and swelling?

Yes. Lyme arthritis commonly affects the knee and may cause substantial swelling, warmth, stiffness, pain, and difficulty walking. Other causes of an acutely swollen knee must also be considered.

Can Lyme arthritis affect a replaced knee?

Lyme arthritis involving a replaced knee has been reported, but it appears to be exceptionally rare. New pain or swelling around a prosthetic joint requires careful evaluation for a conventional bacterial infection and other orthopedic complications.

How is Lyme arthritis in the knee diagnosed?

Diagnosis is based on the clinical presentation, exposure history, Lyme antibody testing, and evaluation of the joint fluid. Synovial fluid PCR may provide additional evidence in selected cases but should be interpreted with the other findings.

Can Lyme arthritis involving a knee replacement be treated without surgery?

In this case report, one patient’s symptoms resolved after 90 days of oral doxycycline without surgery. However, there are no established treatment guidelines for Lyme arthritis involving a prosthetic knee, and several previously reported patients required surgery and antibiotics.

Clinical Takeaway

This case illustrates the diagnostic challenge created when knee swelling associated with Lyme disease develops around a prosthetic joint. Lyme arthritis may resemble a conventional periprosthetic joint infection, but the treatments can be very different.

A conventional bacterial infection, mechanical failure, crystal arthritis, and other causes of knee swelling must be evaluated before deciding that Lyme disease is responsible.

In patients with an unexplained swollen knee—even after knee replacement—Lyme arthritis may warrant consideration when the clinical presentation and exposure history support it.

Related Articles

Lyme disease mimics prosthetic joint infection following knee replacement
5 cases of Lyme arthritis following an operation
MRI can help identify Lyme arthritis in children and avoid unnecessary surgery

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Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention