Right leg knee pain on the inside of the knee straightening or bending pain, may be the medial collateral ligament injury, lumbar disc herniation, osteophytes and other causes. 1. Injury to the medial collateral ligament: If the medial collateral ligament is damaged, it may manifest as pain on the inside of the knee. 2. Herniated lumbar disc: If a herniated lumbar disc compresses the nerve root, pain symptoms may occur in the soft tissues of the leg muscles it innervates. 3. Osteomalacia: If the knee joint develops degenerative lesions, causing osteophytes, it may manifest as joint swelling, pain, and limited joint movement. It is recommended that people with right knee pain go to a regular hospital in time to clarify the cause of the disease and standardize the treatment under the guidance of the doctor, so as not to delay the condition.