Joint Stress Has No Impact on Gout

Obesity is a known risk factor for gout. It's long been assumed that added weight in obesity can negatively affect urate deposits in joints, but according to new research, this does not seem to be the case. 

A 2005 study published inJAMA Internal Medicine found that weight gain since young adulthood was strongly associated with the risk of gout. As well, a reduction in weight of more than 10 pounds appeared to reduce that risk. It is also known that patients who have gout, often also have osteoarthritis affecting joint biomechanics. To address these issues, researchers in New Zealand compared patterns of foot von Mises stress with patterns of urate deposition and they did not find a connection, according to a study published in the Aug. 13, 2015 issue of RMD Open.

For this study, the researchers evaluated the walking patterns and foot pressure of 50 healthy men, 25 of whom had normal body mass index (BMI) of 18 to 25 kg/m, and 25 who had above 25 kg/m BMI. These patterns were compared with urate deposition. Healthy subjects were chosen because earlier research into gait patterns among people with gout were often already altered, even between acute attacks, when the patients did not experience pain or when there were no tophi.

The researchers scanned each subject’s right foot while he was standing barefoot. The men also performed three walking trials over a pressure platform.

The data included bone stress values at:

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• Distal and proximal portions of the first proximal phalanx
• First to fifth metatarsal (MT) heads
• First to fifth MT bases
• Lateral, middle and medial cuneiforms
• Navicular, cuboid, anterior process of calcaneus
• Proximal calcaneus
• Distal talus

​To perform urate deposition analysis, the researchers used data (DECT scans) from a study published in 2014, assessing the diagnostic value of intra-articular and periarticular ultrasound-detected abnormalities in the upper and lower limbs in gout. Bone erosion analysis was performed using published data from a study published in 2010, in which the researchers developed a method of scoring bone erosion in patients with gout, using CT.

​The researchers found that the third metatarsal (MT) head showed the highest average and peak von Mises stress among the men in both the lower BMI and the higher BMI groups. The men with the higher BMI did show higher ground reaction forces, but the foot contact area was also higher and von Mises stress patterns remained similar in both groups.

​However, the first MT head was most affected in patterns of urate deposition and bone erosion, and the third MT head had infrequent involvement, for both average and high BMI groups. “The frequency of urate deposition was less than 10 percent in all bone areas in asymptomatic hyperuricemia,” the authors wrote. “There was no positive relationship between the patterns of urate deposition in asymptomatic hyperuricemia with either average or peak von Mises stress.”

These findings raise more questions for researchers about what factors do really contribute to the preferential sites for gout involvement. “Further exploration of factors, including local bone and joint factors, contributing to development of both asymptomatic and symptomatic MSU crystal deposition will require large prospective studies of people with hyperuricemia,” they concluded.

​Nicola Dalbeth has received consulting fees, speaker fees or grants from the following companies: Takeda, Teijin, Menarini, Pfizer, Ardea, AstraZeneca, Savient, Fonterra, Metabolex.

Disclosures:

1. Choi H, et al. Obesity, Weight Change, Hypertension, Diuretic Use, and Risk of Gout in Men. JAMA Internal Medicine. 2005;165(7):742-748. doi:10.1001/archinte.165.7.742.

2. Dalbeth N, et al. Relationship between tissue stress during gait in healthy volunteers and patterns of urate deposition and bone erosion in gout: a biomechanical computational modelling study.RMD Open 2015;1:e000101 doi:10.1136/rmdopen-2015-000101

3. Naredo E et al. Ultrasound-detected musculoskeletal urate crystal deposition: which joints and what findings should be assessed for diagnosing gout? Annals of the Rheumatic Diseases. 2014;73:1522-1528 doi:10.1136/annrheumdis-2013-203487

4. Dalbeth et al. Development of a computed tomography method of scoring bone erosion in patients with gout: validation and clinical implications. Rheumatology (Oxford) 2011;50:410–16. doi:10.1093/rheumatology/keq335