Final answer:
The biceps femoris is part of the hamstring group which helps extend the hip and contributes to knee flexion, making the statement true.
Step-by-step explanation:
The biceps femoris is part of the hamstring group, which includes three long muscles located on the back of the thigh. The primary function of the biceps femoris is to flex the knee and to aid in the extension of the hip, meaning it helps to move the thigh backwards, not just bend the knee. This muscle group also plays a role in internal and external rotation of the lower leg when the knee is bent. The hammstrings, contrary to the anterior muscles of the thigh, such as the quadriceps femoris group, do not extend the lower leg at the knee; the quadriceps muscles are responsible for this action. The biceps femoris and its hamstring companions indeed help to extend the hip, which confirms the statement posed in the question as true.