Inclusion Criteria:  Have a clear history of knee injury, clinically suspected knee injury, need MRI examination; Arthroscopy or treatment is planned.  Exclusion Criteria:  Patients with the following diseases: rheumatoid arthritis, septic arthritis, tumor, anterior cruciate ligament mucinous degeneration, and articular fibrosis; Previous history of knee surgery; MRI contraindication: patients with metal in body (pacemaker, prosthetic eye, metal implant), pregnancy or claustrophobia; Arthroscopy was not performed after MRI examination for various reasons; The time interval between MRI examination and arthroscopy was more than 2 months.