Osteoarthritis (OA) is a prevalent chronic degenerative joint disorder marked by cartilage degradation, subchondral bone remodeling, and synovial inflammation. Despite its widespread occurrence, effective pharmacological interventions to halt or reverse OA progression remain elusive. Thus, an in-depth understanding of its pathogenesis is imperative for developing novel therapeutic strategies. Sixty-four male Sprague-Dawley rats (8 weeks old, weighing 180-220 g) were randomly assigned to two groups: the anterior cruciate ligament transection (ACLT) group and the sham-operated group. Primary osteoblasts were isolated from the subchondral bone at 0, 4, 8, and 12 weeks after ACLT. Nuclear magnetic resonance (NMR)-based metabolomics was used to elucidate metabolic changes and the underlying mechanisms in osteoblasts. A total of 26 metabolites were identified from the NMR spectra of osteoblasts. Distinct metabolic profiles were observed in the ACLT group at 0, 4, 8, and 12 weeks after surgery. In particular, several differential metabolites were identified, including glucose, lactate, NADP, phosphocreatine, and alanine, as well as eight perturbed pathways, such as alanine, aspartate, and glutamate metabolism, phenylalanine metabolism, and taurine metabolism. Key energy-related metabolites, including glucose, lactate, creatine phosphate, and creatine, were identified as key markers of osteoblast dysfunction in OA, underscoring the profound metabolic perturbations induced by ACL injury. These disturbances in energy homeostasis are strongly implicated in the progression of OA. In addition, branched-chain amino acids emerged as potential biomarkers, further highlighting the metabolic dysregulation associated with the disease. Taken together, the metabolic changes observed in rat osteoblasts following ACL injury reveal a complex interplay between energy and amino acid metabolism, providing critical insights into the pathogenesis of post-traumatic OA and highlighting potential therapeutic targets.