"Tooth Sign"
Degenerative Disease of the Knee

General Considerations

• Degenerative enthesophyte formation on superior aspect of patella as seen on axial or skyline (sunrise) view
• Form on superior and anterior surface of patella
• Site of insertion of the quadriceps tendon
• Frequent finding with degenerative disease

Clinical Findings

• No correlation with patient's clinical symptoms

Imaging Findings

• Saw-tooth projections best seen on axial or skyline view of patella on its superior and anterior surface

Tooth Sign. Vertical ridges (white arrow) arising from superior and anterior surface of patella representing enthesophytes that have formed from degenerative disease in the quadriceps tendon.
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"Tooth" sign in patellar degenerative disease.  Greenspan, A; Norman, A and Tchang, FK. J Bone Joint Surg Am. 1977;59:483-485.