Intra-articular calcium crystal deposition is commonly seen in knee osteoarthritis, but its significance has been debated.
Now, a new study that relied on knee radiographs and bilateral knee CT imaging to evaluate 2,093 participants, including some with and without knee mineralization, has provided some new insights.
Dr. Jean Liew
The study has addressed the longstanding question: Is the calcium deposition a cause or a consequence of the OA? “If it’s a cause, targeting it might be helpful,” Jean Liew, MD, MS, the study’s lead author and assistant professor of medicine at Boston University, said in an interview. “If a consequence of the OA, targeting is not going to help.”
In this new study, because of the use of advanced imaging, the researchers demonstrated a strong relationship of the presence of this calcification with different pain characteristics, said Tuhina Neogi, MD, PhD, professor of medicine and epidemiology at Boston University, the corresponding author of the study who has focused on this research for many years. “This indicates this mineralization is not inconsequential.”
The bottom line? “Calcification in the knee may not be simply inert and an innocent bystander of longstanding OA,” Dr. Neogi said in an interview.
Study details
Dr. Neogi and colleagues evaluated 2,093 participants (mean age, 61 years; 57% female) with a mean body mass index of 28.8 kg/m2. In all, 10.2% of knees had intra-articular mineralization. The data came from the National Institutes of Health–funded longitudinal Multicenter Osteoarthritis Study. At baseline, participants had knee radiographs and bilateral knee CT scans, and pain assessments every 8 months for 2 years. The Boston University Calcium Knee Score was used to score the CT imaging. The researchers longitudinally examined the relationship of the CT-detected intra-articular mineralization to the risk of frequent knee pain, intermittent or constant knee pain worsening, and pain severity worsening. All analyses were adjusted for age, sex, body mass index, race, site, and Kellgren-Lawrence grade.
Dr. Tuhina Neogi
Having any mineralization in the cartilage was associated with a doubling of odds for having frequent knee pain (95% confidence interval, 1.38-2.78), and 1.86 times greater likelihood of more frequent intermittent or constant knee pain (95% CI, 1.20-2.78) over the 2 years of follow-up. Similar results were seen for the presence of any intra-articular mineralization in the meniscus or joint capsule. The higher the burden of mineralization anywhere within the knee was linked with higher odds for all pain outcomes, with odds ratios ranging from 2.14 to 2.21.
Perspective
“Because we used more sensitive imaging to pick up the calcification, we are able to more confidently evaluate this association,” Dr. Neogi said in an interview. The problem with prior studies was their reliance on plain radiographs, which are not sensitive enough to pick up this calcification.
Among the other strengths of the new research, she said, is that it was longitudinal, included more than 2,000 people and used multiple ways to look at the pain experience, getting consistent results.
“Here we are saying there seems to be clinical relevance [to the mineralization]. That’s not so surprising. We know there are other medical conditions in which calcium calcification can cause severe pain and inflammation.” The old term, pseudogout, is now called calcium pyrophosphate deposition disease.
The next steps of research, Dr. Neogi said, are to investigate the link of the mineralization to inflammation and its association to cartilage damage.