Characterisation of first metatarsophalangeal joint osteoarthritis using magnetic resonance imaging

First metatarsophalangeal joint (MTP) joint osteoarthritis (OA) is prevalent, although the pathology of this condition is poorly understood. This study aimed to determine if there were differences in magnetic resonance imaging (MRI) characteristics of the first MTP joint between individuals with and without first MTP joint OA. This cross-sectional study compared 22 participants with first MTP joint OA to 22 control participants without first MTP joint OA (matched for age, sex, and body mass index). Participants underwent MRI of their first MTP joint and osteophytes, bone marrow lesions, subchondral cysts, effusion-synovitis, joint space narrowing, and cartilage loss were documented using an atlas of first MTP joint OA. Associations of MRI characteristics with the presence of first MTP joint OA were then determined. The presence of first MTP joint OA was associated with increased severity of osteophytes (dorsal metatarsal head, plantar metatarsal head, and dorsal proximal phalanx), bone marrow lesions (metatarsal head and proximal phalanx), cysts of the metatarsal head, effusion-synovitis (dorsal aspect), joint space narrowing (metatarsal-proximal phalanx; metatarsal-sesamoids), and cartilage loss. In contrast, there were no statistically significant associations for bone marrow lesions of the sesamoids, cysts of the proximal phalanx, or effusion-synovitis (plantar aspect). Osteophytes, bone marrow lesions, subchondral cysts, effusion-synovitis, joint space narrowing, and cartilage loss are characteristic MRI features of first MTP joint OA. First MTP joint OA is a disease of multiple joint tissues and this has implications for the assessment and management of this condition.