Low bone mineral density is associated with the onset of spontaneous osteonecrosis of the knee

Abstract

Background and purposeThe primary event preceding the onset of symptoms in spontaneous osteonecrosis in the medial femoral condyle (SONK) may be a subchondral insufficiency fracture, which may be associated with underlying low bone mineral density (BMD). However, the pathogenesis of SONK is considered to be multifactorial. Women over 60 years of age tend to have higher incidence of SONK and low BMD. We investigated whether there may be an association between low BMD and SONK in women who are more than 60 years old.MethodsWe compared the BMD of 26 women with SONK within 3 months after the onset of symptoms to that of 26 control women with medial knee osteoarthritis (OA). All the SONK patients had typical clinical presentations and met specified criteria on MRI. The BMDs measured at the lumbar spine, ipsilateral femoral neck, and knee condyles and the ratios of medial condyle BMD to lateral condyle BMD (medial-lateral ratios) in the femur and tibia were compared between the two groups. The medial-lateral ratios were used as parameters for comparisons of the BMDs at both condyles.ResultsThe mean femoral neck, lateral femoral condyle, and lateral tibial condyle BMDs were between x% and y% lower in the SONK patients than in the OA patients (p < 0.001). The mean femoral and tibial medial-lateral ratios were statistically significantly higher in the SONK patients than in the OA patients.InterpretationA proportion of women over 60 years of age have low BMD that progresses rapidly after menopause and can precipitate a microfracture. These findings support the subchondral insufficiency fracture theory for the onset of SONK based on low BMD.

Femoral condyle insufficiency fractures: associated clinical and morphological findings and impact on outcome

“…The high frequency of osteopenia or osteoporosis among our study population, especially in comparison to previously reported rates of osteopenia or osteoporosis in normal adult populations, supports that the impaired bone architecture along the load-bearing surfaces is likely a risk factor for insufficiency fracture [28,29]. However, the degree of abnormality (osteopenia versus osteoporosis) to predispose to fracture remains controversial [10,30]. Additionally, in our study, female gender did show a modest association with progression of FCIF to TKA.…”

“…This discovery prompted a reevaluation of SONK at the femoral condyle [2,5,6]. A spectrum of femoral condylar pathology has since been proposed, with FCIF and osteonecrosis being recognized as distinct entities along this spectrum, and osteoporosis was implicated as a risk factor [2,[7][8][9][10]. Currently, there remains limited knowledge about the clinical findings and morphological abnormalities associated with femoral condyle insufficiency fractures (FCIF).…”

Spontaneous Osteonecrosis of the Knee: A Retrospective Analysis by Using MRI and DEXA

“…These may induce microfracture, thus leading to subcondral insufficiency fracture [2-7] the prognosis of which is thought to be dependent on the lesion as detected in the MRI [8-12], few studies with the combination of BMD and MRI have been reported [13]. In this article, we examined the cause and prognosis of our cases which were initially diagnosed as SONK by using MRI and DEXA.…”

Cross-sectional and longitudinal associations between systemic, subchondral bone mineral density and knee cartilage thickness in older adults with or without radiographic osteoarthritis

“…Subchondral BMD (sBMD) and subchondral bone remodelling also play important roles in OA pathology 10 11. Some studies have demonstrated that knee OA was associated with lower sBMD,3 12 while another study documented that patients with high tibial sBMD had increased joint space narrowing (JSN) over 1 year 13…”