Doxycycline May Slow Progression of Osteoarthritis

It may moderate the deterioration of knee joints

Study results reported in the July 2005 issue of Arthritis & Rheumatism suggested that treatment with the antibiotic doxycycline may slow the progression of osteoarthritis. Doxycycline is an antibiotic belonging to the class of medicine called tetracyclines.

Pharmacist handing prescription bag to a customer
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About the 2005 Doxycycline Study

Researchers compared the use of doxycycline to placebo, after enrolling more than 400 obese women with knee arthritis as study participants. The study participants were randomized into two groups, receiving either 100 mg of doxycycline twice daily or a placebo for up to 2.5 years. Researchers analyzed the impact of doxycycline on the joint space of the affected knee.

Following 16 months of treatment, results indicated that the average loss of joint space in the affected knee was 40% less among participants taking doxycycline than those who took a placebo. At the end of the two and a half year period, the loss of joint space was 33% less in the group who took doxycycline than in the placebo group. Doxycycline was also associated with less patient-reported increases in knee pain. Researchers acknowledged, though, that the average level of pain was low in both groups.

The 2005 study was the first major study of doxycycline as a potential treatment for osteoarthritis. At the time, it was said that more studies would be needed to confirm the results.

Comments From Dr. Zashin

On the subject of doxycycline and osteoarthritis, rheumatologist Scott Zashin, M.D. commented, "First of all, this is a unique study in that it was a relatively long-term study that looked at a medication to not only relieve pain but also prevent progression of osteoarthritis of the knee. While the study did not clearly show that oral doxycycline was effective in reducing pain, there was evidence that there was less progression of osteoarthritis (i.e., less loss of cartilage) in patients on the antibiotic. The authors make it clear that the antibiotic was felt to work based on its anti-inflammatory properties, and not due to its antibacterial effect."

Dr. Zashin continued, "What does this study mean for patients with osteoarthritis? Two clinical issues important to patients and doctors include whether the medication relieves joint discomfort and whether or not the patient may require a joint replacement in the future. Based on this study, it is difficult to recommend long-term doxycycline for relief of symptoms. On the other hand, it is possible that patients taking the antibiotic may be less likely to require a joint replacement in the future due to a decrease in joint damage on radiograph. Unfortunately, to answer this question, a much longer study would be needed. Some questions to consider are whether patients would need to remain on antibiotics indefinitely to help decrease joint damage and prevent subsequent joint replacement and what are the potential side effects from this long-term regimen. The other question is whether or not a 30-month treatment with the drug will, in itself, decrease the chances that in the long run, those patients would be less likely to require surgery. Hopefully, this cohort of patients can continue to be studied in the future to help answer the questions."

2012 Cochrane Review of Doxycycline for Osteoarthritis

In 2012, an update was published of a Cochrane review of doxycycline for osteoarthritis originally published in 2009. The review considered evidence in medical literature that had examined the effects of doxycycline on pain and physical function in patients with osteoarthritis of the hip or knee when compared to placebo. Only two studies involving 663 people were found to be relevant and were included in the review. The review concluded that the effect of doxycycline on symptoms of osteoarthritis pain is not clinically significant. Study participants rated their pain improvement as 1.9 on a scale of 0 (no pain) to 10 (extreme pain) compared to an improvement of 1.8 points for placebo patients after 18 months.

Results of the review also revealed that the effect of doxycycline on physical function was not clinically significant. The improvement in physical function was just 1.4 versus 1.2 points on the 10 point scale for participants who took doxycycline versus placebo, respectively.

It was also noted in the review that 20% of participants who took doxycycline experienced side effects (of any type) compared to 15% of those who took a placebo. Ultimately, the benefit of doxycycline pertaining to loss of joint space that was initially reported was deemed small and of questionable clinical relevance in the Cochrane review. 

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