Can Ellipsoid Sign be One of the Earliest Findings of the Medial Femoral Condyle Chondromalacia of Knee Antero Posterior X-Ray?

BACKGROUND/PURPOSE OF THE STUDY: Aim of the study was to investigate whether ellipsoid sign (ES) in the region corresponding to the cartilaginous facet of the medial femoral condyle (MFC) indicates early cartilage lesion. The finding has not been defined in the literature yet.
METHODS: The study was performed retrospectively with 50 patients who underwent articular cartilage examination and arthroscopy between 2015 and 2018. Patients were divided into two according to the presence or absence of ES. There were 24 patients in case group (Group A) and 26 patients in controls (Group B). Weight-bearing cartilage areas of MFC in the region where ES was found in both groups were classified according to arthroscopic Outerbridge classification (OC) and compared statistically with each other.
RESULTS: There was no significant difference in terms of age, gender and alignment between Group A and Group B (p > 0.05). All OC grades were higher in Group A (p  <  0.001). Positive correlation between ES and MFC chondromalacia grade was detected (r: 0.671, t: 6.266, p < 0.05).
CONCLUSION: ES, which refers to the difference in bone density in MFC seen in antero-posterior (AP) X-Ray, is a result of changes in subchondral bone due to chronic cartilage loss. ES detected on AP X-Ray may help in early diagnosis of medial femoral articular cartilage chondromalacia, even at grade 0 or 1. We recommend searching for ES, as the earliest symptom of chondromalacia, which occurs even before MRI lesions. Future studies may reveal additional information about ES. © Indian Orthopaedics Association 2020.