03/02/2026
Have you noticed that when the MCP joint is hyperextended, you aren’t able to full extend you IP joints? 🤔 A relative motion splint can assist in correcting this patterning 🙌🏼
The lumbricals originate from the flexor digitorum profundus (FDP) tendon and insert into the extensor hood. When the MCP joint hyperextends, tension in the FDP increases and is transmitted through the lumbricals. Instead of helping extend the IP joints, the lumbricals are pulled volarly, drawing the extensor hood forward and causing IP joint flexion during MCP extension.
A relative motion splint helps correct this by holding the affected fingers in slight MCP flexion compared to the others, which prevents MCP hyperextension, reduces FDP tension, and decreases abnormal lumbrical pull. With less stress on the extensor hood, the IP joints can straighten more easily during finger extension.