Popliteal cyst is characterized by swelling and pain in the popliteal fossa, and in severe cases, it may prevent knee flexion and extension, and cause severe pain or weakness of the lower limbs on the affected side. 1. Swelling in popliteal fossa: This is a typical symptom of popliteal cyst, which can be seen as a round lump, which feels fluctuating and has smooth edges when touched. If the cyst is large, it may hinder the flexion and extension of the knee joint, resulting in movement difficulties. 2. Pain: If the cyst compresses the nerves, it may cause chronic persistent pain or numbness. If the cyst ruptures, it may cause severe pain on the affected limb. 3. Movement disorders: in severe cases, it may prevent knee flexion and extension, and the affected side of the lower limb may have severe pain or weakness. It is recommended that patients with popliteal cysts go to the hospital in time. Popliteal cysts are generally benign lesions, after active treatment, most patients can be cured.