Tuberculous Monoarthritis of the Knee Joint

Knee pain can be very discomforting, causing the person to be uncomfortable as they suffer the excruciating pain from it. This pain can arise as a result of hitting one's knee on an object, or it can be caused by some other factors. This post is gotten from an article discussing Tuberculous monoarthritis of the knee joint published on Canadian Medical Association Journal (CMAJ) in the year 2023.

According to the article, a 47 year old man had been suffering knee pain in Toronto. He had immigrated to Canada from the Philippines 16 years ago. Since he had no previous medical condition, or performed any surgeries in the past, we could say that he was healthy, so he thought it was just a minor problem but this time around the pain would not go.

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At the hospital, he experienced excruciating pain, and his knee was swollen and painful that he couldn't walk as any movement came with severe pain. After examination Given these findings, bacterial septic arthritis was suspected. What this mean is that bacteria start to grow inside the lubricating synovial fluid of the joint. Since there are no much immune cells in the joint to fight against bacteria, an infection to the joint can be terrible.

With an X-ray and a CT scan, it showed that the knee bone had erosion and although his blood work was normal, his CRP (C-Reactive Protein) was high which indicated high level of inflammation in the body. With this identified, the cause and a solution is needed at the time.

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To identify what could be the problem, fluid from the knee was taken in a procedure known as Arthrocentesis where the skin is sterilized and frozen after which a large needle is inserted into the knee joint to get the synovial fluid from the patient. This fluid is taken to the lab where it is examined though a cell counter which showed that there was a high level of white blood cells present in them. using a microscope, there were no crystals in the fluid, and using gram stain and acid fast stain didn't show any sign of bacterial infection.

The fluid sample was cultured and the patient was placed on Antibiotics before the culture result arrived and the culture result didn't show any sign of bacterial or fungal infection. What are the possible causes of Erosion Monoarthritis and High CRP? They can be as a result of infection which could be bacterial, fungal, viral, systemic infection, and so on, it can also be autoimmune, Tumor, Crystal induced, and other things like trauma.

Blood work for certain antibodies came back negative which means it could possibly not be an autoimmune disease, and since there were no crystals formed, it could not be crystal induced but then we still have other options like tumor (cancer). Scanning his entire body was done for the purpose of cancer but there were no cancers instead the scan found scar tissues in the patient's lungs.

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Polymerase Chain Reaction (PCR) test was performed on the patient and it came back positive confirming that the patient was suffering from Tuberculosis. In the case of Tuberculosis, gram staining only come out positive less than 40% when tested, and in the case of culture, it can take up to 8 weeks before it begins to grow.

If we know TB to be a lung infection, how did it get to his knee? The patient was exposed to a person suffering from TB back in his country, and it was transferred but his immune system was strong enough to curtail the bacteria but it wasn't killed, rather it was just engulfed but sine it had mycolic acid, it was able to reproduce inside the macrophages.

The macrophages begin to produce granuloma which are inflammatory cells that hold the Tuberculosis. While the immune system places it in a dormant phase, it can become active if the immune cells of the patient is weak. At this stage, the tuberculosis gets into his blood vessels and travel to his knee where it began to eat up the patient's bone.

Treatment of Tuberculosis includes using these four antibiotics which are Rifampin, Isoniazid, Pyrazinamide, and Ethambutol for 6 months compared to regular bacterial infection that requires 3 to 5 days for treatment. It is very difficult to treat and it can resist drugs but in the case of the patient, it wasn't drug resistant, and the patient was treated for 9 months.

Reference

https://www.nhsinform.scot/illnesses-and-conditions/infections-and-poisoning/tuberculosis-tb/
https://www.ncbi.nlm.nih.gov/books/NBK441916/
https://www.cmaj.ca/content/cmaj/195/22/E782.full.pdf
https://www.sciencedirect.com/topics/medicine-and-dentistry/tuberculous-arthritis
https://www.hindawi.com/journals/crirh/2021/7751509/
https://ped-rheum.biomedcentral.com/articles/10.1186/1546-0096-6-15
https://www.cdc.gov/tb/topic/basics/default.htm
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3762461/
https://www.ncbi.nlm.nih.gov/books/NBK557666/