A bulge on the inside of the knee may be caused by meniscus cyst, knee joint effusion or osteoarthritis, etc. Corrective treatment should be carried out according to the specific disease. 1. Meniscus cyst: After the meniscus tissue appears cystic tissue, it may form a bulge on the inner side of the knee, and sometimes the local cyst may gradually increase in size, and the treatment needs to be surgical to remove the diseased tissue cleanly. 2. Knee joint effusion: when there is effusion in the knee joint, the bulge on the inner side of the knee will also appear, you can have the joint cavity punctured to extract the effusion under the guidance of the doctor, or use physical therapy and other ways to relieve the problem. 3. Osteoarthritis: after the occurrence of osteoarthritis, the tibial plateau medial margin hyperplasia, will also form a bulge in the inner side of the knee, in the progress of the disease to a certain extent, may need to carry out artificial joint replacement therapy, the bulge will also be eliminated. When a bulge appears on the inner side of the knee, the nature of the bulge needs to be clarified first, and the bulge needs to be treated actively.