There are many reasons for left knee pain without redness or swelling, and the common reasons are meniscus injury, osteoarthritis, osteophytes and so on. 1. Meniscus injury: meniscus injury is the knee joint in different triggers under the integrity and continuity of the meniscus has been damaged caused by the meniscus injury, meniscus injury symptoms can be mild only the inner side of the knee joint pain, no restriction of activities, no redness and swelling. 2. Osteoarthritis of the knee: it is a chronic disease that progresses gradually. In the early stage of the disease, there will be joint pain after cold, exertion or slight trauma, with mild symptoms, not accompanied by redness and swelling, and then there will be joint stiffness and pain, which may be accompanied by limp, and then the pain will be reduced gradually after activities. 3. Osteomalacia: Degenerative changes in the knee joint can lead to osteophytes on the inner side, which can also lead to pain without redness or swelling on the inner side of the knee joint. Left knee pain without redness or swelling may have other causes such as knee joint medial collateral ligament injury, etc., it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, and standardize the treatment under the guidance of the doctor.