Magnetic resonance imaging definitions of key entheseal pathologies.
| Pathology | Definition |
|---|---|
| 1. Intratendon hypersignal (entheseal tendonitis) | Signal characteristics consistent with increased water content/inflammation* within the tendon/ligament/aponeurosis close to its insertion |
| 2. Peritendon hypersignal (entheseal peritendonitis) | Signal characteristics consistent with increased water content/inflammation* in the soft tissues surrounding the tendon/ligament/aponeurosis, close to its insertion |
| 3. Bone marrow edema (entheseal osteitis) | Bone lesion with ill-defined margins and signal characteristics consistent with increased water content/inflammation,* close to the tendon/aponeurosis insertion |
| 4. Bursitis † | Signal characteristics consistent with increased water content/inflammation* in an above normal–sized bursa |
| 5. Tendon/aponeurosis thickening | Abnormal thickening of the tendon/aponeurosis close to its insertion |
| 6. Enthesophyte | Abnormal bone formation at the insertion of tendon/ligament/aponeurosis insertion into the bone |
| 7. Bone erosion (entheseal bone erosion) | A sharply marinated bone lesion, with typical signal characteristics** and a visible cortical break, located close to the tendon/ligament/aponeurosis insertion |
| 8. Intra-tendon hypersignal on T1W | Increased signal in T1-weighted (T1W) sequence within the tendon/ligament/aponeurosis close to its insertion |
↵† This lesion should only be assessed in entheseal regions in which a relevantly located bursa is present.
↵* High signal intensity on short-tau inversion recovery/T2wFS images and/or above normal post-gadolinium enhancement on T1W images.
↵** On T1W images without contrast injection: loss of normal low signal intensity of cortical bone and loss of normal high signal intensity of marrow fat. T2wFS: T2w fat-suppressed [images].