The most common causes of knee pain are chronic injury, acute injury, allergic reaction and degenerative factors, as follows: 1) Chronic injury: excessive knee activity can cause cumulative damage to the articular cartilage, resulting in significant pain in both knees. 2) Acute injury: for example, both knees are subjected to external forces at the same time, causing local soft tissue damage, joint capsule damage, meniscal damage, ligament damage, fractures and dislocations. The patient has rheumatoid arthritis, gouty arthritis, bacterial dysentery, allergic purpura, tuberculosis infection, etc., which can lead to painful symptoms in both knees. 4, degenerative factors: such as the presence of primary or secondary osteoarthritis, will lead to the presence of significant pain symptoms on both sides of the knee.