Isolated subcortical trabecular bone injury (bone bruise) has rarely been described. Our purpose is to report a series of patients who had a history of traumatic injury, knee effusion, normal radiographs, and initial equivocal physical examination for ligament and meniscal integrity, and who were found to have isolated injury of the trabecular bone on magnetic resonance imaging. We evaluated demographic data, physical examination findings, radiographs, magnetic resonance imaging, and clinical outcome for 23 patients. Follow-up data included time to return to preinjury activity level, International Knee Documentation Committee activity level rating before and after injury, and postinjury Lysholm scores. All magnetic resonance imaging scans were negative for associated grade III meniscal lesions and ligament injury. Time to return to preinjury activity level was under 7 months in 96% of the patients. Postinjury International Knee Documentation Committee rating was unchanged in 91% of patients. Postinjury Lysholm score was 90 or more in 91% of patients. We propose that the recognition of these injuries is important because magnetic resonance imaging can distinguish them from meniscal or ligament injury requiring surgical intervention (arthroscopy). If detected on magnetic resonance imaging as an isolated injury, surgical arthroscopy is unnecessary since these patients can be expected to recover well in the short term with restricted weightbearing and initial activity modification.