Objectives: To evaluate the spectrum and frequency of MR findings of the first metatarsophalangeal joint (MTPJ) in asymptomatic volunteers.
Methods: MR imaging of 30 asymptomatic forefeet was performed with a dedicated extremity 1.5-Tesla system. Participants were between 20 and 49 years of age (mean ± SD: 35.5 ± 8.4 years). Two radiologists assessed cartilage, bone, capsuloligamentous structures, and tendons of first MTPJs on MR images.
Results: Cartilage defects were observed in 27 % (n = 8) of first MTPJs, most frequently located at the base of the proximal phalanx (23 %, n = 7), whereas cartilage defects of the metatarsal head (13 %, n = 4) and the metatarsosesamoid compartment were rare (0 %-3 %, n = 0-1). Bone marrow oedema-like signal changes were present in 37 % (n = 11) and subchondral cysts in 20 % (n = 6) of first MTPJs. Hyperintense areas on intermediate-weighted sequences (range: 30-43 %, n = 9-13) and on fluid-sensitive sequences with fat suppression (range: 33-60 %, n = 10-18) within the medial and lateral collateral ligament complex were common. Plantar recesses (77 %, n = 23) and distal dorsal recesses (87 %, n = 26) were frequently observed.
Conclusions: Cartilage defects, bone marrow oedema-like signal changes, subchondral cysts, plantar recesses, and distal dorsal recesses were common findings on MRI of first MTPJs in asymptomatic volunteers. The collateral ligaments were often heterogeneous in structure and showed increased signal intensity.
Key points: • Cartilage defects of asymptomatic first metatarsophalangeal joints were common on MRI. • The collateral ligaments were often heterogeneous in structure and showed increased signal intensity. • Areas of increased signal intensity within the flexor and extensor tendons were rare. • These observations need to be considered in MR examinations of symptomatic cases.