Walking a lot of pain on the outside of the thigh may be caused by physiological factors, but also may be a symptom of certain diseases, such as trauma, sciatica, lumbar disc herniation, soft tissue tumors and so on. 1. Physiological factors: If you don’t pay attention to exercise, lack of exercise, short-term sudden strenuous physical activity, there will be a large accumulation of lactic acid in the thigh muscles, lactic acid produces acidic metabolites, stimulating the peripheral nerves caused by the walking thigh muscle pain on both sides. 2. Pathological factors (1) Trauma: If there is an impact injury or fall in the thigh area, it can lead to muscle pain on both sides of the thigh, and there may be trauma or bruising, which may lead to fracture in serious cases. (2) Sciatica: It is a group of syndromes with pain along the sciatic nerve pathway and its branches. The main symptom is pain, which may radiate from the lower back and buttocks to the back of the thighs, the outside of the calves and the back of the feet. (3) Lumbar intervertebral disc herniation: due to the degeneration of lumbar intervertebral discs, rupture of fibrous ring, protrusion of nucleus pulposus, irritation and compression of nerve roots, it can lead to lumbago, sciatica, numbness of limbs and other symptoms, and compression of bony nerves can lead to symptoms of muscle pain on both sides of the thighs. (4) Soft tissue tumor: originated from mesenchymal tissues, located in soft tissues, mainly manifested as painless lump, fever, weight loss and other symptoms, due to the local muscle mass or cyst, compression of the surrounding muscle tissues can lead to muscle pain on both sides of the thigh. If the muscle pain on both sides of the thigh, it is recommended to consult a doctor in time to clarify the diagnosis and avoid delaying the condition.