Notes on Post-Infection Arthritis and Fibromyalgia Pain 27 Oct 2026
1. Arthritis, Infected Knee, or Lyme Disease?
In 2024, I did two things to my right knee that turned out to be stupid.
1) I mowed down the very tall grass at the bottom of the hill in August, without putting on bug repellent. I had a rash on the antecubital area behind the knee that started a few days after I mowed the lawn. It was mildly itchy, but not in the shape of a target. I ignored it, and it went away after about a week.
2) After getting a flat tire in the early morning (in Kamloops), I walked a mile or so around the town to keep warm until the garages opened up. The next day, I had a bubble filled with fluid on my right knee with pain and reduced range of motion. These symptoms were consistent with lyme arthritis.
The fluid bubble and pain stayed with me, increasing and decreasing in a cycle. Because I could not document a target-rash, doxycycline was not provided and I was advised to use NSAIDs like Ibuprofen or Aleve.
I got some relief from Aleve, but the cycles of swelling continued and were gradually getting worse. I found that I had to go up stairs by using only my good leg to step up on the next stair. I was limping, and my walking speed decreased.
In early 2025, got a referral to another physician who injected my knee joint with Solu-Cortef, and assured me that ‘because of [my] age it was certainly arthritis. You will see great improvement after the shot.’
The shot did help for a couple of days. Then my knee got much worse. I was at work at the end of the day before the Good Friday Statutory Holiday. My prescriber’s medical office was closed, as were the offices of most other prescribers. I was in excruciating pain and having real difficulty standing up. I was also running a temperature. Fortunately work was slow. I was able to reach a teledoctor and convinced him to prescribe a course of Doxycycline to rule out the theory of infectious arthritis. I took the first dose when I got home.
About 45 minutes later, I was surprised by achiness in all my joints and the ends of my fingers and toes. I was also somewhat short of breath, and my heart rate increased. This reminded me of something I had read about;
When spirochetes are rapidly killed off by antibiotics, the patient often experiences a Herxheimer-Jarisch reaction– Achy joints, fever and shortness of breath are caused by the now-dead spirochetes clogging up capillaries throughout the body. Natural processes clear them out, and then the patient is fine.
Sure enough, in about 36 hours, most of the symptoms were gone and the fluid on my knee had reduced a lot in size. My knee’s range of motion began to improve over the rest of the year, and I began to limp less.
I told my primary care prescriber about all this, and she ordered a Lyme Disease screening panel. She also made me get a test for Syphilis, though I tried to tell her THAT was a waste of money. Both were negative. “You have never had Lyme Disease,” she told me in the follow up appointment. “It’s just arthritis. You are getting old.”
“Why did it get better after the Doxycycline?” I asked. She didn’t know, but was sure it was not Lyme Disease.
In September of 2025, the knee pain increased somewhat and the fluid bubble began to grow again. Again, after a chat with a tele-doctor, I took a course of Doxycycline. No Herxheimer-Jarisch reaction this time, but the pain and the bubble decreased over the course of antibiotics. After that, it stayed down.
Today, in October 2026, I have very minimal pain or no pain in the knee. I have full range of motion, and I am able to alternate legs while climbing stairs.
How Do We Explain This?
I’m not sure. It’s not a clear picture.
1. Rule out infectious arthritis
Lyme Disease Borrelia is a spirochete, like syphilis. And like syphilis, if you kill off a major infection all at once with antibiotics, you get a Herxheimer-Jarisch reaction.
There are about 20 tick-borne diseases, not just Lyme borrelia. I might have gotten another of these, such as STARI, that might respond to antibiotics but not show up on the Lyme screening test.
2. Rule out osteoarthritis
It’s true that I’m old, and joints wear out, sooner or later.
3. Torn meniscus or other joint damage.
I did suddenly do a lot of exercise that day in 2024. Possibly I could have torn a ligament or meniscus.
Assessment:
Considering the above, arthritis due to infection seems to be the best fit for the course of my illness. I had symptoms consistent with Lyme Disease. Injecting the joint with a steroid made things briefly better, but then much worse–as would happen when steroids are given to someone with an untreated infection. And, taking antibiotics made things dramatically better. Osteoarthritis does not get better, until you get the joint replaced.
It’s somewhat disheartening that the only progress I made to geting recovery in my joint happened in spite of the medical system, not because of it. It may not have been Lyme disease, but to me, the indications are that it was some sort of infection that was, fortunately, killed off by Doxycycline. That in mind, we turn to consider Fibromyalgia;
2. The Mystery of Fibromyalgia
Chronic pain, sensitivities to substances that produce flare-ups, chronic fatigue. That’s some of Fibromyalgia. At this writing, there is no simple explanation of why it happens, and certainly no wonderful treatment modalities.
Duloxetine and Pregabalin are given to lessen symptoms, They don’t work well–
https://www.fibrocanada.ca/en/treatments
It IS somewhat similar to my knee experience, so that made me wonder if there is any evidence that Fibromyalgia is something that happens to people who had an infection. Maybe not every infection, just some of the time for some people.
Sure enough–
https://www.healthrising.org/blog/2021/10/27/fibromyalgia-post-infectious-disease/
When you look into it, a LOT of people who had Giardia from dirty water ended up with Fibromyalgia, Chronic Fatigue Syndrome, and/or Irritable Bowel Syndrome.
There are reports that GLP-1 drugs like Mounjaro/Tirzepatide and Ozempic/Semaglutide reduce symptoms of Fibromyalgia.
https://pubmed.ncbi.nlm.nih.gov/41578948/
They even appear to reduce symptoms of Long COVID; My wife’s long-COVID symptoms largely resolved after she began to take Semaglutide for her diabetes;
https://pmc.ncbi.nlm.nih.gov/articles/PMC13425107/
Fibromyalgia may be an autoimmune disease like rheumatoid arthritis;
https://www.verywellhealth.com/autoimmunity-neuroinflammation-in-fibromyalgia-5197944
If so, drugs that treat autoimmune diseases like Etanercept may be able to back down the autoimmune response and give symptom relief.
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