The relationship between functional disability and MRI-inflammation has been studied for the hands, but has not been well established for the feet, even though walking-difficulties are common. Therefore we studied whether walking-difficulties were associated with MRI-inflammation at metatarsophalangeal(MTP)-joints in early arthritis patients, at diagnosis and during 24-months follow-up.
532 consecutive patients presenting with early arthritis reported on presence and severity of walking-difficulties (HAQ-question 4a, scale 0-3), and underwent unilateral contrast-enhanced MRI of MTP(1-5)-joints at baseline. 107 patients had clinical and MRI-data at follow-up (4-, 12- and 24-months). MRI-inflammation (synovitis, tenosynovitis and osteitis) was scored in line with RAMRIS. At baseline the association of walking-disability with MRI-inflammation was assessed using regression. Longitudinally the association between a change in walking-disability with a change in MRI-inflammation was studied with linear mixed models.
At baseline, 81% patients with walking-disabilities had MRI-inflammation at MTP-joints, versus 68% without walking-disabilities (P<0.001). Total MRI-inflammation (i.e. the sum of tenosynovitis, synovitis and osteitis) was associated with severity of walking disability (β=0.023, P<0.001). Studying the MRI-features separately, tenosynovitis, synovitis and osteitis were all univariable associated with severity of walking-disability (P<0.001, P<0.001 and P=0.014 respectively). Multivariable, the association was strongest for tenosynovitis. During follow-up a decrease in MTP-inflammation was associated with a decrease in walking-disability (β=0.029, P=0.001): in multivariable analyses only tenosynovitis was independently associated (β=0.073, P=0.049).
Of the different inflamed tissues in MTP-joints, predominantly MRI-detected tenosynovitis was associated with walking-disabilities. Likewise a reduction in tenosynovitis related to a decrease in walking-disabilities. This increases our understanding of the involvement of tenosynovitis in walking-disabilities in early arthritis.

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