IS OSGOOD-SCHLATTER DISEASE TRULY A BENIGN KNEE CONDITION? A PILOT STUDY DEMONSTRATING INCREASED POSTERIOR TIBIAL SLOPE

BACKGROUND: Osgood-Schlatter disease (OSD) is a traction apophysitis caused by repetitive strain and chronic avulsion of the secondary ossification center of the tibal tuberosity from the patellar tendon. PURPOSE: The aim of this study was to determine if OSD is associated with increased posterior tibial slope (PTS). METHODS: A total of 40 knees with OSD and 32 control knees examined by the senior author between 2008 and 2019 were included. Patients aged 10 to 15 years old with clinical diagnosis of OSD supported by radiographic findings on lateral X-ray and MRI were eligible. Age- and sex-matched subjects with history of anterior knee pain but no evidence of OSD on clinical exam and no fragmentation of the tibial tubercle on lateral X-Ray and MRI were included in the control group. PTS was defined as the angle between the reference line 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 X-Rays by two blinded investigators. Interrater reliability of posterior tibial slope measurements between the two examiners was evaluated using intraclass correlation coefficient (ICC). Independent-sample student t-test was used to compare PTS in the OSD and control knees. RESULTS: Mean age at time of lateral radiograph was 12.6 ± 1.6 years and 51% (37/72) of knees were male. There were no differences in age, sex, and laterality of knees between the OSD and control groups. Mean PTS was significantly higher in the OSD group (12.23º ± 3.58º) compared to the control group (8.82 º ± 2.76 º, p<0.001) (Figure 1). ICC was 0.931 (95% confidence interval, 0.890 to 0.957) for measurement of PTS between the two examiners, indicating almost perfect interrater reliability. CONCLUSION: This study is the first to identify an association between OSD and increased PTS. The clinical implications of this novel finding have not yet been elucidated. However, several studies have demonstrated that increased PTS is a risk factor for ACL injury and re-tear. It may be speculated 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.