Bilateral distal femoral sclerotic lesions in elderly women: a distinct benign imaging pattern associated with fat necrosis and dystrophic calcification.

OBJECTIVES

To characterize a previously unreported pattern of bilateral distal femoral sclerotic lesions in elderly women and to describe its radiographic, CT, MRI, and histopathologic features.

MATERIALS AND

METHODS

This retrospective study included patients with bilateral distal femoral sclerotic lesions identified on knee radiographs between 2018 and 2023. Lesions related to known skeletal disorders were excluded. Two musculoskeletal radiologists independently assessed lesion location and morphology. Available CT, MRI, and histopathologic findings were reviewed. Clinical and laboratory data were compared with age-matched controls. Interobserver agreement was assessed using Cohen's κ.

RESULTS

Thirty women (mean age, 76.7 ± 7.7 years) were included, with 60 knee radiographs, 13 CT scans, 10 MRI examinations, and one histopathologic specimen. On radiographs, sclerotic changes were exclusively lateral in 40%, predominantly lateral in 33.3%, and central in 26.7% of knees. Lesion morphology was linear (36.7%), nodular (10%), popcorn-like (8.3%), or mixed (45%), with almost perfect interobserver agreement (κ ≥ 0.88, p < 0.0001). MRI demonstrated a reticulonodular fibrous-like pattern aligned with the trabeculae within fat-like marrow signal intensity on T1- and T2-weighted images. Histopathologic examination of a surgically sampled similar tibial lesion demonstrated necrotic adipocytes with interstitial dystrophic calcification, without extensive trabecular bone formation or osteonecrosis. Clinical and laboratory parameters did not differ between patients and controls.

CONCLUSION

Bilateral distal femoral sclerotic lesions associated with fat necrosis and dystrophic calcification may represent a distinct benign imaging pattern in elderly women. Further studies are needed to determine whether recognition of this bilateral pattern may avoid unnecessary investigations.

KEY POINTS: QuestionDo bilateral distal femoral sclerotic lesions in elderly women represent a distinct benign imaging pattern? FindingsIn 30 elderly women, bilateral distal femoral sclerotic lesions exhibited a consistent imaging pattern without aggressive features. MRI revealed a reticulonodular fibrous-like pattern within a background of fat-like marrow signal on T1-weighted images. Clinical relevanceRecognition of the characteristic bilateral distribution and benign imaging features may help avoid unnecessary follow-up examinations or biopsies.