Bilateral Osteochondrosis of the Primary Patellar Ossification Centers in a Young Athlete

A Case Report

Aisha S. Dharamsi, MD; Rebecca L. Carl, MD


Clin J Sport Med. 2014;24(1):80-82. 

In This Article


The etiology of osteochondrosis is multifactorial, caused by abnormal development, acute injury, and/or overuse of the growth plate and surrounding ossification centers.[9] The patella develops by endochondral ossification at primary and secondary ossification centers. Primary centers are responsible for longitudinal bone growth; secondary centers contribute to spherical growth. The patella forms around the ninth week of embryonic life as a cartilaginous mass. Primary ossification occurs between 3 and 6 years old; secondary centers appear in early adolescence and close during early adulthood.[10]

The most common sites of osteochondrosis associated with anterior knee pain occur at secondary centers including the tibial tubercle (Osgood-Schlatter disease) and/or the inferior patellar pole (Sinding-Larsen and Johansson disease). Osteochondrosis of the primary ossification center (Köhler's disease of the patella), however, is infrequently described in the literature.

Most cases of this clinical entity have been reported in individuals with associated osteochondrosis of secondary ossification centers.[2,3,5] In these instances, determining the etiology of anterior knee pain becomes complicated as it is well known that osteochondroses of secondary centers are commonly associated with pain. In these cases, it could be argued that the concurrent findings of osteochondrosis of the primary patellar ossification center could be incidental with no clear relationship to pain.

A literature review identified 4 reported cases of patellar osteochondrosis isolated to the primary ossification center.[6,8] Three of these were part of a case series[6] of males between 5 and 6 years old who presented with bilateral anterior knee pain, no history of trauma, and x-ray findings consistent with osteochondrosis isolated to the primary center. The fourth case[8] was an incidental finding in an 8-year-old male with no pain complaints seen in trauma clinic after a trivial left knee injury. Before his evaluation, unilateral x-rays resulted in a misdiagnosis of patellar fracture; further examination included contralateral x-rays confirming incidental findings present bilaterally.

Our case seems to be the first case of isolated painful bilateral osteochondrosis of the primary patellar ossification centers identified radiographically by both x-ray and MRI. Because our clinical evaluation was negative for traumatic, infectious, or inflammatory processes, nor was there evidence of a concurrent overuse or biomechanical injury, we are confident in attributing this patient's anterior knee pain to bilateral primary patellar osteochondrosis. Although rare, this condition is an important part of the differential diagnosis in a skeletally immature individual with anterior knee pain not attributable to more common causes. Similar to other osteochondroses, this condition seems to be self-limited with a benign course; long-term follow-up, however, is certainly warranted.