Effect of Zoledronic Acid and Alendronate on Bone Edema and Pain in Spontaneous Osteonecrosis of the Knee: A New Paradigm in the Medical Management.

Objective  The aim of the present study was to determine the effect of combined zoledronic acid and alendronate therapy on bone edema and knee pain in cases of spontaneous osteonecrosis of the knee. We report our experience with this treatment. Methods  A retrospective case series of 11 patients with spontaneous osteonecrosis of the knee confirmed by magnetic resonance image (MRI). The patients were treated with a single dose of 5 mg of intravenous zoledronic acid combined with 35 mg twice a week of oral alendronate, for 16 weeks. The visual analogue scale scores were noted before the beginning of the therapy, at 8 weeks, and at 16 weeks of follow-up. The size of the bone marrow edema adjacent to the lesion was measured on T2-weighted MRI coronal images at the beginning of the therapy and at 16 weeks. Results  The average visual analogue scale score at 0 weeks was of 7.72, and of 0.81 at 16 weeks of therapy; the difference was statistically significant ( p  = 0.03). The mean bone marrow involvement at 0 weeks was of 80%, which reduced to 11.81% at 16 weeks of therapy. This change was statistically significant ( p  = 0.03). Conclusion  Our data shows that the combination therapy causes early pain relief and reduction of the bone edema, and it is safe, effective and well-tolerated for a painful disease entity like spontaneous osteonecrosis of the knee.