Findings: A lateral view of the knee demonstrates an irregular cortical margin of the inferior patella and calcified density extending into the infrapatellar tendon. No evidence of joint effusion or displaced fracture is seen.

Diagnosis: Finding-Larsen-Johansson disease.

Discussion: The irregular calcification seen at the inferior margin of the patella results from irregular ossification of the immature inferior patellar pole thought to result from persistent or repeated minor traction injury at this site. This is a chronic injury usually occurring in active young males, 10 to 12 years of age who experiences anterior knee pain that increases with activity.

This is the inferior patellar equivalent of Osgood-Schlatter's disease which can also occur at the superior patellar-quadriceps tendon junction infrequently.

References:
Kirks D. Practical Pediatric Imaging, 3rd Edition.
Lippincott-Raven, Philadelphia; 1998:491-492.

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