| Grade 1 | Distal avulsion of volar plate from base of middle phalanx. Hyperextension of PIP joint. (swan-neck deformity) Proximal avulsion of checkreins less common and can cause pseudoboutonniere deformity |
| Grade 2 | Volar plate injury extends to collateral ligaments. Dorsal subluxation produces more instability. Volar plate tilting with detachment of collateral ligament |
| Grade 3 | Fracture-dislocation of distal attachment of volar plate. Stable injury: fragment involves <40% of articular surface with integrity of collateral ligament attachment Unstable: dorsal subluxation with larger fracture fragment |