A Case of Spontaneous Osteonecrosis of the Knee with Early and Simultaneous Involvement of the Medial Femoral Condyle and Medial Tibial Plateau

Bilateral Spontaneous Osteonecrosis of Knee with Concomitant Medial Femoral and Tibial Condyle Involvement - A Rare Presentation and Short Review

Introduction:

Osteonecrosis of knee is classified as primary spontaneous osteonecrosis of knee (SPONK) and secondary osteonecrosis of knee. Primary SPONK usually involves medial femoral condyle (MFC). Incidence of medial tibial plateau (MTP) is only 2% among the patients with SPONK and simultaneous involvement of MFC and MTP is very rare.

Case Report:

We report a very rare case of 45-year-old female with SPONK affecting both MFC and MTP simultaneously with subchondral insufficiency fractures. She presented with pain in both the knees and difficulty in walking since 1 year. Physical examination revealed decreased range of motion and local tenderness over MFC and medial tibial condyle. Subchondral fracture with articular surface collapse of MFC with joint space narrowing and varus deformity was seen on X-ray in both the knees. Sclerosis was seen in the medial tibial condyle bilaterally. Magnetic resonance imaging showed characteristic focal hyperintense areas surrounded by band like hypointense areas in both MFC and MTP which was suggestive of subchondral collapse with ill-defined bone marrow changes. X-ray of both knees revealed SPONK in Koshino’s Stage IV and Carpintero’s Stage IV. Bilateral total knee replacement (TKR) was planned. First left knee was operated. A cruciate retaining type of TKR was done. Two weeks, later right side TKR was operated. MFC of right side also had a large osteochondral fragment which was excised to leave defect with depth more than 2 cm. Defect was reconstructed with bone graft obtained from posterior condylar cuts. Posterior stabilized type of knee replacement component was used along with femoral extender stem. Histopathological examination revealed necrotic bone surrounded by an area of fibrovascular granulation tissue on both the femoral and tibial sides. Patient has good functional outcome at 2 years follow-up.

Conclusion:

Concomitant SPONK of MFC and MTP in bilateral knee is very rare and in advanced stages TKR can provide good radiological and functional outcome. Furthermore, pre-operative assessment of bone defects is necessary and appropriate use of augments (extender stem or metal wedges) is crucial.

Subchondral insufficiency fracture of the knee: grading, risk factors, and outcome

OBJECTIVE

To propose an magnetic resonance imaging (MRI) grading system for subchondral insufficiency fracture of the knee (SIFK) to predict outcome and assess risk factors.

MATERIALS AND METHODS

A total of 50 SIFK patients were retrospectively reviewed utilizing two MRI examinations approximately a year apart and compared them with 51 control subjects. A grading system was introduced that classifies lesions as low- vs high-grade. Lesion location 3D dimensions, extent of bone marrow edema (BME), location of meniscal tears and associated extrusion, degree of chondrosis and among other parameters were stratified according to lesion grade and compared with follow-up examinations. Statistical analyses were performed (Pearson's correlation, binary logistic regression, and Chi-squared analysis).

RESULTS

The majority of SIFK lesions were low-grade (LG; 78%) and most of them (70%) were observed in the medial femoral condyle. Predictor variables comparing low-grade and high-grade SIFK lesions included meniscal tear (p = 0.01), degree of extrusion (p < 0.003), chondrosis (p = 0.01), medial chondrosis grade (p = 0.001), medial femoral condyle (p = 0.01), surface collapse (p < 0.0001), marrow edema improvement (p < 0.0001), first MRI anteroposterior dimension (p = 0.001), transverse dimension (p < 0.001), and ellipsoid volume (p = 0.02). Predictor variables found to be significantly different between controls and patients were meniscal tear (p = 0.024), location of the medial meniscal tear (p < 0.0001), degree of extrusion (p < 0.0001), chondrosis (p < 0.0001), joint effusion (p < 0.0001), Baker's cyst (p < 0.0001), knee lock (p = 0.03) and buckle (p = 0.01), and history of trauma (p = 0.01).

CONCLUSION

A SIFK grading system for MRI is introduced. Surrogate markers of high-grade lesions include medial meniscus posterior root tears with associated moderate to severe extrusion, high-grade chondrosis, larger lesion sizes (anteroposterior/transverse), and articular surface collapse. Improvement of BME on follow-up was highly predictive of low-grade disease.

Subchondral Insufficiency Fracture in the Lateral Compartment of the Knee in a 64-Year-Old Marathon Runner

A 64-year-old marathon runner presented to our clinic with a history of worsening pain in her left knee. Following magnetic resonance imaging, the diagnosis of subchondral insufficiency fracture of the knee (SIFK) was made. A course of conservative management via bisphosphonates was initiated. The patient successfully recovered and returned to full athletic function, having recently returned to competitive marathon running. This article aims to present this unusual case of lateral compartment SIFK and summarise the literature on this uncommon condition.