Dislocation of the extensor tendon at the MP joint is uncommon. We reported dislocations of both long-finger and ring-finger extensor tendons ulnarward, and the left little finger radialward. Most authors found the lesion to be tear of expansion hood or intertendinous fascia. But, our patient had thinning of radial expansion hood of the left long-finger, normal expansion hood of the right long and ring-fingers. And, both intertendinous connection between the index and long fingers were absent. So, we find that the lesion is not tear of expansion hood but absence of intertendinous connection. We treated dislocation of extensor tendons operatively with intertendinous connection. No recurrence of dislocation is present 10 months after surgery.