Table 1.
Reported MR features for selected benign foot lesions.
| Lesion type | T1-weighted intensity | T2-weighted intensity | Contrast enhancement | Other MR features |
|---|---|---|---|---|
| Gouty tophi | Isointense-to-muscle [11], homogenously low-to-intermediate T1 signal | Heterogenous low-to-intermediate T2 signals [10], [11] | Variable appearance with gadolinium [11] | First metatarsophalyngeal or other joint may show evidence of articular gout including articular erosions, cartilage sparing, periarticular edema, joint effusions [10], [11] |
| Rheumatoid nodules | Low T1 signal [12] | High T2 signal [12] | — | Features of rheumatoid arthritis such as joint effusions, marrow edema, subchondral cyst, cartilage thinning, and pannus formation may be present [12]. Typically nodules appear in patients with advanced disease who have concommitant corticosteroid-induced osteopenia [12] |
| Pigmented villonodular synovitis | Inhomogenous low T1 signal [13] | Low T2 signal [13] | — | Predilection for location between digits and characteristic blooming on gradient echo imaging [8] |
| Hemangioma | Low-to-intermediate T1 signal [8] | High T2 intensity [8] | Marked enhancement [8] | Often appear morphologically as multilobed, septate lesions [8] |
| Angiomyoma | Low T1 signal [8] | Heterogenous T2 signal [8], [13] | — | Hypointense lining may be evident due to presence of cystic capsule [9] |
| Plantar fibromatosis | Iso-to-low T1 signal | Low-to-intermediate T2 signal [14] | Variable enhancement [14] | Nodules afflict plantar aponeurosis [14] |
| Morton's neuroma | Low-to-intermediate T1 signal [8] | Low T2 signal [8] | Mild contrast enhancement [12] | Perineurally located usually [5], classically at metatarsal head of second and third digits [8], [9] |
Surfers' knots can be differentiated from most other benign foot lesions because they exhibit ill-defined T1 hypointensity and speckled T2 hypointensity, with only mild enhancement after contrast administration. They are distinguished from pigmented villonodular synovitis, which exhibits similar signal characteristics, because blooming artifact is not evident on gradient echo imaging.