Common causes of thigh to calf lateral tendon pain include lumbar disc herniation, tendon strain, and pyriformis syndrome. 1. Herniated lumbar intervertebral disc: the nucleus pulposus of the herniated intervertebral disc compresses the nerve root at the back, and the nerve is stimulated, resulting in soreness from the thigh to the lateral tendon of the calf. 2. Tendon strain: The tendon is strained due to strenuous activities, resulting in spasm and edema, causing soreness from the thigh to the lateral calf tendon. 3. Piriformis syndrome: the sciatic nerve is stimulated by the adhesion and compression of the piriformis muscle, which manifests as radiating pain in the distribution area of the nerve root, radiating from the lateral thigh to the lateral calf. Caused by thigh to calf lateral tendon pain, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, and standardized treatment under the guidance of the doctor.