1-Extensor tendon subluxation or dislocation can trigger other tendons dislocation or subluxation,
2-The head of metacarpal bones will migrate dorsally==> flexion deformity,
3-Ulnar dislocation of the extensor tendon==> adduction at MCP J==> ULNAR DEVIATION,
4-Lack of MCPJ Extension ==> over-activity of interensic muscles of hand==> hyper-extension of PIP joints==> swan neck deformity,
5- Abnormal Biomechanics==> deformity despite control of RhA activity by medicines,
6-When you do MSK US assessment of RhA patient, don't forget to do dynamic scan,
7- Abnormal biomechanics due to inflammatory attenuation of ligaments==> red flag of future damage.