Muscle knots in the Semitendinosus are typically located in the upper posterior thigh, just below the gluteal fold, and can refer pain down the back of the thigh, into the knee, and even the upper calf, often mimicking hamstring strain or sciatic pain. Muscle knots in the Semimembranosus, which lies just beside the Semitendinosus, also cause pain in the posterior thigh, radiating to the medial knee and upper calf, and may feel like a deep ache that worsens with walking, sitting, or lifting. People often describe the discomfort as a tight, pulling sensation that limits flexibility and makes activities like squatting or sprinting feel strained.