Description of the disease (onset, main symptoms, hospital visited, etc.): More than one year old. Left knee pain when walking. 306 hospital MRI, impression: degenerative changes in left knee; effusion in left knee; degeneration of half meniscus (degree I-II); medial collateral ligament injury (grade I); currently only treating degenerative changes, not yet involving treatment of effusion, meniscus, collateral ligament. Please explain the degree of severity requested in the title. Degenerative degeneration of the knee, also known as knee osteoarthritis, commonly known as old cold leg, is a common disease in the elderly, with recurring conditions, easily induced by weather changes, exertion, etc. It manifests itself in many forms, such as osteophytes, meniscal degeneration, joint effusion due to synovitis, free bodies, degeneration of collateral ligament damage, cartilage exfoliation, joint stiffness, etc. It manifests in slightly different forms in different people. There are three degrees of meniscal injury, degree I is the mildest, it is the signal change inside the meniscus parenchyma, no special treatment is needed; degree II is the injury extends from the meniscus parenchyma to the outer edge of the meniscus, whether treatment depends on the extent of the injury, degree III is necessary for surgical treatment, arthroscopic meniscoplasty can be done. Your case should be relatively mild and does not require surgery. Usually, you should pay attention not to make frequent knee flexion exercises, such as climbing, stairs, squatting, etc. First degree ligament injury means that there is edema signal, but the fibers are intact and continuous, no special treatment is needed.