Subchondral insufficiency fracture of the knee: unicompartmental correlation to meniscal pathology and degree of chondrosis by MRI.

Objective: To assess the relationship between low- and high-grade subchondral insufficiency fracture of the knee (SIFK) and meniscal tear/type/location, severity of meniscal extrusion, grade of chondrosis, and extent of surrounding edema-like marrow signal intensity.

Materials And Methods: Our retrospective study included 219 patients with knee pain and SIFK seen on MRI. SIFK lesions were categorized from grade 1 to 4 with a low grade (1 and 2) vs high grade (3 and 4) distinction. Associations between SIFK grade, location, lesion dimensions, edema-like marrow signal intensity, incidence of meniscal tears/type/location, and chondrosis (grade 0 to grade 4), as well as patients' age and weight, were assessed.

Results: Our analysis consisted of 115 males and 104 females with 17% of the patients showing grade 1 SIFK, 59% grade 2, 16% grade 3, and 8% grade 4. No chondrosis or low-grade chondrosis was mostly present in patients with low-grade SIFK (68.9%), whereas high-grade chondrosis was mostly present in patients with high-grade SIFK lesions (65.4%) (p < 0.01). Further sub-analysis demonstrated that high-grade SIFK was associated with high-grade chondrosis in the same compartment (p < 0.01) but not in the adjacent compartment. There was a significant difference in the extent of edema-like marrow signal intensity between the two groups, with high-grade SIFK more frequently demonstrating severe edema-like marrow signal intensity compared to low-grade SIFK (p < 0.01).

Conclusion: High-grade SIFK lesions are associated with unicompartmental high-grade chondrosis.