BRUSSELS – Vitamin K deficiency may increase the risk for developing knee osteoarthritis and for forming knee cartilage lesions, judging from the findings of a 30-month study of nearly 1,200 people at risk for knee osteoarthritis.
This apparent role of low vitamin K levels in susceptibility to knee pathology raised the question whether vitamin K supplementation for deficient individuals might be a “simple, effective preventive agent,” Dr. Tuhina Neogi said at the annual World Congress on Osteoarthritis.
Dr. Tuhina Neogi
“The next step is an intervention trial,” said Dr. Neogi, a rheumatologist at Boston University. “Taken together, there is enough biological plausibility that vitamin K could play a role. Osteoarthritis is multifactorial, but this could be one component. If [dietary supplementation] proves effective, it would be something easy for people to do for themselves.” Foods high in vitamin K are green, leafy, and cruciferous vegetables.
Vitamin K works as a cofactor in the carboxylation of several proteins that are involved in bone and cartilage formation and maintenance. Results from prior studies showed that low vitamin K intake and low blood levels were linked with prevalent radiographic features of hand and knee osteoarthritis. The new study made the first longitudinal examination of a potential link between plasma levels of vitamin K at baseline and incident osteoarthritis and associated pathology.
The investigators examined data that was collected from people enrolled in the Multicenter Osteoarthritis (MOST) study who had an elevated risk for knee osteoarthritis at entry but had not yet developed the disease. MOST enrolled more than 3,000 people who had osteoarthritis or were at risk for it starting in 2003 at two U.S. sites. The 1,180 people who were included in the study averaged 62 years of age; 62% were women, and their average body mass index was about 30 kg/m2. Dr. Neogi and her associates defined vitamin K deficiency as a plasma level of phylloquinone less than 0.5 nmol/L. (Normal is 0.5-1.2 nmol/L.) At baseline, 9% of the study participants without osteoarthritis had vitamin K deficiency.
The researchers made incidence osteoarthritis the primary end point, defined as development of a knee Kellgren-Lawrence (KL) grade of 2 or higher (including knee replacement). All people included in the analysis had a KL grade less than 2 at baseline. During 30 months of follow-up, 15% of the participants developed osteoarthritis.
In an analysis of whether or not participants developed knee osteoarthritis, those with vitamin K deficiency at baseline had a 43% increased risk, after adjustment for age, sex, BMI, bone mineral density, and vitamin D level at baseline. This increased risk just missed reaching statistical significance. Dr. Neogi suggested that this may have been a power issue, with too few vitamin K–deficient participants in the database.
An additional analysis that took into account the extent of knee osteoarthritis showed statistically significant links with vitamin K deficiency. Those who developed osteoarthritis in both knees had a significant, nearly threefold increased risk of having vitamin K deficiency at baseline, compared with those who developed osteoarthritis in one knee during follow-up. Those who had both knees affected at follow-up had a significant, twofold increased risk of vitamin deficiency, compared with people who did not develop any knee osteoarthritis, she reported at the congress, which was organized by the Osteoarthritis Research Society International.
The vitamin K–deficient participants also had a statistically significant, nearly threefold increased risk of developing new cartilage lesions on their knee MRI scans that were consistent with developing osteoarthritis. They also had a 77% increased risk for showing osteophytes on their follow-up MRI scans, but this difference was not statistically significant.
Dr. Neogi said that she had no disclosures.