Patella partita.

Patella partita is a malformation of the knee cap, generally characterized by one or a few vertical lines of discontinuity in sagittal planes, caused by incomplete ossification within a single ossification center. In other cases, disorder of ossification in frontal planes results in frontal subdivision of the patella. While patella partita is sometimes diagnosed as a coincidental radiographic finding, in other cases, especially in elderly individuals, it is a finding associated with symptoms which require treatment.