The present invention relates to the discovery that the expression levels of some RNA molecules, comprising messenger RNA (mRNA), non-coding RNA (ncRNA) and/or microRNA (miRNA), and protein can be used as a diagnostic signature to predict or monitor the bone healing ability in an acutely injured subject or in a chronic nonunion subject. In certain embodiments, the invention relates to methods and compositions useful for differentiating between a nonunion, slow healing, and/or normal healing of a fractured bone and treatment recommendations. The invention further includes a kit comprising biomarker probes for assessing the bone healing ability in an acutely injured subject or in a nonunion subject after receiving therapeutic treatment.