Objective To summarize the characteristic manifestations in the middle and old aged people with meniscus injury and the outcome of the treatment under the arthroscope. Methods Fifty-two patients, aged 52-58 years, with meniscus injury to a total of 57 knee joints, were diagnosed and treated under the arthroscope. The history of their knee diseases was 1-21 years. Horizontal tearsoccurred in 19 knee joints, degenerative tears in 13 knee joints, complex tears in 9 knee joints, longitudinal tears in 5 knee joints, oblique tears in 4 knee joints, radial tears in 4 knee joints, and flap tears in 3 knee joints. Three meniscus tears were sutured and 54 meniscus tears were cut fully or partly under thearthroscope. Results All the postoperative patients were followed up for 6-15 months, and the average follow-up period after operation was 9 months. According to the DONG Tianxiang’s standards for the therapy under the arthroscope, the excellent result was achieved in 39 knee joints, good in 12 knee joints, and fair in 6 knee joints, with no failure. The excellent and good rate was 89.5%. Conclusion The clinical manifestations of meniscus injury are not typical in the middle and old aged people. The therapeutic effect with the help of the arthroscope is satisfactory with an advantage of minimal traumatic invasiveness to the knee joint.