The discomfort of swelling inside the knee may be caused by trauma, arthritis, infectious lesions, tumors and other pathological reasons. 1. Trauma: Trauma causes meniscus injury, anterior and posterior cruciate ligament injury, joint fracture, local oozing, edema, bleeding, etc., the patient may feel uncomfortable swelling inside the knee. 2. Arthritis: such as osteoarthritis, rheumatism, rheumatoid osteoarthritis, the patient may feel uncomfortable swelling inside the knee. 3. Infectious lesions: due to bacterial, viral and other causes of knee joint infection, infectious synovitis and other diseases, patients may appear swelling, oozing, fluid accumulation, patients may appear inside the knee feeling uncomfortable swelling. 4. Tumor: Due to the compression of the surrounding tissues by bone tumor or soft tissue tumor in the knee joint, patients may feel uncomfortable with swelling inside the knee. There may be other reasons for the discomfort of swelling inside the knee, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or therapy.