No statistically significant association could be found between gout and osteoarthritis (OA) of the hand, knee, or foot in a small study, researchers said.
However, the analysis, published in BMC Musculoskeletal Disorders, provided hints that people with gout may be more likely than those without gout to have OA affecting the small joints of the hands and feet, and less likely to have large joint OA at the knee. With just 53 gout patients included in the study, it may have been underpowered to find clear associations.
In the study, believed to be the first to examine the relationship between gout and radiographic OA across multiple joint sites, Megan Bevis, of Keele University in Staffordshire, England, and colleagues used baseline data from three prospective population-based cohorts of patients age 50 and older with pain in the hand, knee, and foot.
The analysis included 53 people with gout who were identified though primary care medical records. Each of these was matched based on age, gender, and study cohort to four participants without gout (the total in the nongout group was 211 since one patient with gout could only be matched to three controls.)
All study participants had analysis of the 16 joints in each hand while 27 gout and 108 nongout subjects had knee analysis and 25 with gout and 99 without gout had foot analysis. The researchers used relevant atlases to assess and score radiographic OA.
Hand OA was defined as Kellgren and Lawrence (K&L) grade ≥ 2 affecting interphalangeal joints (IPJs) on at least two rays on each hand. Moderate to severe hand OA was K&L grade ≥ 3 on at least two rays on each hand.
Patellofemoral (PF) joint OA was defined as K&L grade ≥ 2 on the skyline view and/or the presence of a definitive superior or inferior patellar osteophyte (Burnett grade ≥ 1) on the lateral view in either knee. Tibiofemoral (TF) joint OA was defined as K&L grade ≥ 2 on the posterior-anterior (PA) view and/or the presence of definitive osteophyte (Burnett grade ≥ 1) on the posterior tibial surface on the lateral view in either knee.
OA at each of the five foot joints first metatarsophalangeal joint [1stMTPJ], first and second cuneometatarsal joints [CMJ], navicular first cuneiform joint [N1stCJ], and talonavicular joint) was defined as a Menz grade ≥ 2 for osteophytes or joint space narrowing (JSN) on either the dorso-plantar or lateral view in either foot.
The researchers adjusted the analyses for body mass index (BMI) and diuretic use in all three analyses, and further adjusted for hand pain in the hand analysis and knee pain in the knee analysis. They did not adjust for foot pain in the foot analysis as all subjects had foot pain.
In the hand analysis, there was no statistically significant association found between gout and radiographic hand OA on univariable analysis or after adjustments. Although nonsignificant, those with gout showed trends toward having nodal hand OA (adjusted odds ratio [aOR] 1.46; 95% confidence interval [CI] 0.61-350), and having eight or more hand joints affected with moderate to severe radiographic hand OA (aOR 3.57; 95% CI 0.62-20.45).
The knee analysis, which excluded a patient with gout who had missing x-ray data and the matched controls, found no statistically significant associations between gout and knee OA in either unadjusted or adjusted analyses. However, the results suggested that subjects with gout might be less likely to have TF (aOR 0.44; 95% CI 0.15-1.29) and PF (aOR 0.70; 95% CI 0.22-2.22) OA than those without gout, the researchers said.
In the foot analysis, again there was no statistically significant associations between gout and OA. Patients with gout, however, had four times the odds of having three or more foot joints affected with radiographic OA (aOR 4.00; 95% CI 0.99-16.10).
And although a nonsignificant finding, those with gout were more likely to have foot OA affecting at least one joint or a specific joint (the 1stMTPJ, the N1stCJ, and the TNJ) compared with those without gout.
"1stMTPJ involvement is not surprising as it is a common site for both OA and gout, and an association with OA has been suggested as a possible explanation for the striking predilection of gout for this joint," the team wrote.
They explained that the frequency of OA at individual foot joints may reflect the association of gout with generalized OA, or that the pain associated with gout could alter biomechanics of the foot, potentially predisposing to subsequent OA.
"Further research is needed to understand the relationship between gout and OA, using robust case definitions based on crystal identification and imaging," the authors concluded.
A possible limitation of the study was its inadequate statistical power. Other weaknesses were that the study involved secondary analyses of data from existing cohorts and relied on primary care records for a diagnosis of gout.
Reached for a comment, Jasvinder Singh, MD, MPH, of the University of Alabama at Birmingham, said the study is important since the relationship between gout, the most common inflammatory arthritis, and OA, thought to be the most common non-inflammatory arthritis, is "a very understudied subject."
Although the study's lack of statistical significance could be because there is no true relationship, Singh said he believes it is because the study had too few patients with gout, and so lacked the power to adequately test the hypothesis that there is an association with OA.
The lack of statistical power, however, does not mean that the results are not clinically meaningful, he said: "I think the study brings to light potential meaningful clinical associations that need to be investigated" in studies with a larger sample size of gout patients.
Such studies, he added, may conclude that the associations in the current study that did not quite meet statistical significance, "actually are going to turn out to be significant."
The authors reported no financial disclosures.
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