Increased Posterior Tibial Slope in Patients With Osgood-Schlatter Disease: A New Association

Background: Osgood-Schlatter disease (OSD) is a traction apophysitis of the tibial tubercle caused by repetitive strain and chronic avulsion from the patellar tendon. No widely accepted anatomic risk factors have been associated with OSD. Purpose: To determine if OSD is associated with increased posterior tibial slope (PTS). Study Design: Cross-sectional study; Level of evidence, 3. Methods: Forty knees with OSD and 32 control knees examined by the senior author between 2008 and 2019 were included. Patients 10 to 15 years of age with a clinical diagnosis of OSD and available lateral radiograph and magnetic resonance imaging (MRI) were eligible. Age- and sex-matched patients with a history of knee pain but no evidence of OSD on clinical examination and without significant pathology on lateral radiograph and MRI were included in the control group. PTS was defined as the angle between a reference line perpendicular to the proximal anatomic axis and a line drawn tangent to the uppermost anterior and posterior edges of the medial tibial plateau. Measurements were carried out in duplicate on true lateral radiographs by 2 blinded investigators. Interrater reliability of PTS measurements was evaluated using intraclass correlation coefficient (ICC). The independent samples t test was used to compare PTS between the OSD and control knees. Results: The mean age was 12.6 +/- 1.6 years and 51% (37/72) of the knees were from male youth. There were no differences in age, sex, and laterality of knees between the OSD and control groups. The mean PTS was significantly higher in the OSD group (12.23 degrees +/- 3.58 degrees) compared with the control group (8.82 degrees +/- 2.76 degrees; P < .001). The ICC was 0.931 (95% CI, 0.890-0.957), indicating almost perfect interrater reliability. Conclusion: This study identifies an association between OSD and increased PTS. The clinical implications of this finding have not yet been elucidated. It may be speculated that in patients with OSD, stress from the extensor mechanism through the patellar tendon loads the anterior portion of the tibia disproportionately to the posterior segment, thereby resulting in asymmetric growth and an increased PTS.