
The basilar joint of the thumb is between the thumb metacarpal and the trapezium. This joint in critical for proper thumb function. For this reason arthritis in this joint can be quite problematic.

When artritis develops in the basilar joint of the joint the thumb can start getting a "zig-zag" type of a deformity. This progresses as the arthritis worsens.

On physical exam, there can be significant pain with direct palpation, or with what is called the "grind test". In this test the thumb metacarpal is rotated on the trapezium.

Various treatment options are available.