Osteoarthritis is the most common form of arthritis, and is widely considered to be a disease caused by simple wear and tear. However, the latest research suggests that local inflammation may be an important aspect of the disease.
INTRODUCTION
Osteoarthritis is a common condition that makes a person’s joints stiff and painful, particularly in the morning. It is caused by thinning of the cartilage within the joints, which allows the bones to rub against each. Joint swelling and pain are frequent symptoms. It is the most common of all the different types of arthritis, and typically becomes more common as people get older.
WHAT DID THE AUTHORS HOPE TO FIND?
The authors wanted to see whether they could identify inflammation in the joints of osteoarthritis patients using a general marker of inflammation called C-reactive protein. C-reactive protein is a normal protein found in the blood, and is involved in maintaining a healthy immune system. When a person has inflammation in their body for any reason, levels of C-reactive protein rise in response, and this can be measured with a blood test. The authors also hoped to find out whether there was any relationship between the level of C-reactive protein and the signs and symptoms of osteoarthritis that patients reported.
WHO WAS STUDIED?
The authors searched and reviewed 32 previously published studies that included 6,440 patients with osteoarthritis in 12 countries.
HOW WAS THE STUDY CONDUCTED?
A systematic review aims to identify all the published evidence on a particular topic and draw it together into one summary. This paper also included a meta-analysis, which means that statistical analyses have been performed on the results in order to be sure that the conclusions being drawn are meaningful.
The authors used major electronic databases and clinical trial registries to search for trials and studies that reported studies of inflammation in osteoarthritis patients and were published between 1992 and 2012. The search gave a long list of 1272 articles. Of these 32 had the correct type of information and were included in the review.
WHAT WERE THE MAIN FINDINGS OF THE REVIEW?
The review found that serum C-reactive protein level is higher in people with osteoarthritis than in normal healthy people. Higher levels of C-reactive protein level were associated with symptoms of osteoarthritis such as pain and an inability to move the joint, but not with changes to the joint that are visible on X-ray such as narrowing of the joint spaces. The authors concluded that inflammation may play a greater role in osteoarthritis than has previously been thought.
ARE THESE FINDINGS NEW?
Other studies have previously found that C-reactive protein is slightly raised in people with osteoarthritis. But these findings are new in the context of considering osteoarthritis to be more than just a wear and tear disease. The findings clear up this traditional misconception and suggest that inflammation may play a greater role than we previously thought.
HOW RELIABLE ARE THE FINDINGS?
The major limitation of the review is that there is variation in the outcomes that are reported in original studies included – for example, different study designs or different techniques for measuring the levels of C-reactive protein in the blood, and different ways in which the statistics had been calculated in the original studies. Also, there are other factors which may have affected the C-reactive protein levels in patients, such as being overweight, but the authors looked at the results split out for patients who were overweight or not overweight, and there was still a link between C-reactive protein levels and osteoarthritis in both groups.
WHAT DO THE AUTHORS PLAN ON DOING WITH THIS INFORMATION?
There are more studies planned to examine the relationship between a number of inflammatory markers and structural changes in the knee joints of people with osteoarthritis. It is hoped that it will be possible to see a clear picture of the impact that inflammation has on features of osteoarthritis such as cartilage loss and bone damage.
WHAT DOES THIS MEAN FOR ME?
At present, there is no effective drug treatment that can stop osteoarthritis getting worse. These results open the door for the possibility of using anti-inflammatory drugs for treating osteoarthritis in the future. It is hoped that more research might help to develop treatments that target inflammation and relieve the disease symptoms – ultimately stopping the osteoarthritis joint damage and avoiding patients needing joint replacement surgery.
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Date summary prepared: April 2015
Summary based on research article published on: 20 December 2013
From: Jin, X. et al. Circulating C-reactive protein in osteoarthritis: a systematic review and meta-analysis. Ann Rheum Dis 2015;74:703–10. doi:10.1136/annrheumdis-2013-204494
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