In the total examination of the knee, degenerative changes and
ossification in the quadriceps tendon easily recognized on the lateral
roentgenogram may cause confusion in diagnosis when seen on the axial view.
Vertical ridging of the osteophytes at the patellar insertion of the
quadriceps tendon can resemble dentate structure ("tooth" sign). Two
hundred and fifty examinations of the knee in different age groups were
reviewed and several anatomical sections of the quadriceps-patella
insertion were studied. The "tooth" sign represents the relief of severe
osteophyte formation in the bundle of the quadriceps tendon at its
insertion into the patella.