Subchondral Insufficiency Fractures and Osteonecrosis of the Knee

Subchondral insufficiency fractures of the knee (SIFK) arise when normal physiological loads exceed the weakened structural capacity of the subchondral bone, leading to microfracture, pain and bone marrow oedema. In many cases these lesions heal with conservative management, but a subset progress to subchondral insufficiency fractures with osteonecrosis (SIF-ON), characterised by compromised blood supply, bone collapse and rapid cartilage degeneration. Age-related bone mineral density loss, varus malalignment, meniscal root tears and focal overload of the medial femoral condyle or tibial plateau are key risk factors. Magnetic resonance imaging (MRI) enables early detection through marrow oedema patterns and subchondral low-intensity lines, while plain radiographs may reveal late collapse. Clinical management spans from protected weight bearing, pharmacological bone-strengthening and rehabilitation to joint-preserving osteotomies or partial joint replacement when collapse is imminent. Recognition of SIFK and its distinction from primary osteoarthritis or complex regional pain syndrome is critical to preventing irreversible joint deterioration and guiding appropriate treatment.

Research from Nature Portfolio

Advances in imaging have refined lesion assessment by comparing cone beam computed tomography (CBCT) with high-field MRI. Recent work demonstrates that CBCT offers superior delineation of subchondral plate integrity, accurately grading trabecular fractures and subtle areas of collapse that MRI may under- or overestimate. High reproducibility of CBCT grading supports its use in clinical decision-making, particularly when determining the threshold for surgical intervention versus conservative care. These findings underscore the importance of precise imaging to optimise outcomes in patients with SIFK.

Subchondral Insufficiency Fractures and Osteonecrosis of the Knee publication trend

The graph below shows the total number of articles in subchondral insufficiency fractures and osteonecrosis of the knee across all publications each year (not limited to Nature Index journals).

Technical terms

Subchondral bone: The layer of bone immediately below articular cartilage that supports joint loads.

Bone marrow oedema (BME): A fluid-like signal on MRI indicating marrow inflammation or stress reaction.

Osteonecrosis: Localised bone death due to compromised blood supply, often leading to collapse.

Subchondral plate: The thin cortical layer separating articular cartilage from deeper trabecular bone.

Cone beam computed tomography (CBCT): A low-dose CT modality providing high-resolution images of bone microarchitecture and fracture lines.

References

1. Subchondral insufficiency fractures, subchondral insufficiency fractures with osteonecrosis, and other apparently spontaneous subchondral bone lesions of the knee—pathogenesis and diagnosis at imaging. Insights into Imaging (2023).
2. Advantages of cone beam computed tomography for evaluation of subchondral insufficiency fractures of the knee compared to MRI. Scientific Reports (2024).
3. Osteoporosis, Osteoarthritis, and Subchondral Insufficiency Fracture: Recent Insights. Biomedicines (2024).
4. Spontaneous Osteonecrosis of the Knee: State of the Art. Journal of Clinical Medicine (2022).