Figure 13. (a) Abscess arising from joint. Sagittal T1 weighted image demonstrating a rounded low signal mass (arrows) which appears to communicate with the first metatarso-phalangeal joint. (b) Sagittal short tau inversion recovery (STIR) image demonstrating a round fluid signal collection overlying the first metatarsophalangeal joint. There is periarticular oedema in the first metatarsal head indicating septic arthritis.