Potential Utility of SPECT/CT for Early Detection of Spontaneous Osteonecrosis of the Knee.

Spontaneous osteonecrosis of the knee (SONK) is the most common phenotype of osteonecrosis of knee joints in older adults. Early diagnosis with appropriate management is crucial for improving the prognosis of the SONK. We present SONK in bone scintigraphy and SPECT/CT in 65-year-old man with sudden worsening knee pain and normal radiographs. SPECT/CT revealed intense uptake in subchondral area of left femoral medial condyle, which can be differed from progressed osteoarthritic change of the knee joints suspected on planar scintigraphy. Subsequently performed MRI showed characteristic finding of SONK. Total knee replacement arthroplasty was performed with final histological diagnosis of SONK.