The hypotheses for this study are (1) that T1ρ and T2 will be significantly elevated in the lateral side of ACL-injured knees immediately after injury (indicating damage caused by initial injury), and will not fully recover at 6-month, 1-year follow ups; (2) that T1ρ and T2 will be significantly elevated in the medial side of ACL-injured knees at 1-year follow-up; and (3) that differences in the bio-marker expression patterns can be correlated with the initial MRI findings, which would provide information regarding the full spectrum of intra-articular pathology and the subsequent clinical outcomes.