The etiology and pathogenesis of popliteal cysts in children are extremely complex and are usually either primary popliteal cysts or secondary popliteal cysts. There are no obvious predisposing factors.
1. Primary popliteal cyst: Various reasons lead to the increase of intra-articular fluid, the pressure can be increased after the synovial fluid into the popliteal fossa bursa, when the pressure in the joint cavity is abnormally high, the joint fluid will flow out of this fissure, so that the bursa will be enlarged.
This fissure has a unidirectional flow valve mechanism, which ensures the unidirectional flow of joint fluid into the capsule and makes it difficult to flow back into the joint from the capsule, resulting in the formation of popliteal cysts.
2. Secondary popliteal cysts: usually caused by arthritis in the joint, meniscus injury or other ligamentous injuries that lead to the formation of joint effusion.
After the pressure of the effusion reaches a certain level, it can be extruded out of the joint capsule through the living flap structure of the medial joint capsule at the back of the knee joint at the same time. The flap structure can only go out but not in, and the joint fluid enters into the posterior part of the joint through the flap and slowly gathers and develops into a popliteal cyst.
Children with popliteal cysts are advised to go to the hospital in time and be treated under the guidance of the doctor.