Are the hamstrings a two-joint muscle group and is their hip function influenced by knee position?

• A. Yes, they are a two-joint muscle group and their hip function is influenced by knee position
• B. No, they are single-joint muscles
• C. They are three-joint muscles
• D. They are only knee extensors

Answer: (A)

The hamstrings cross two joints—the hip and the knee. They run from the pelvis to the lower leg and work to extend the hip and bend the knee. Because they span both joints, the angle of the knee changes the length and tension of the hamstrings when they act on the hip. When the knee is more extended, the hamstrings are longer across both joints, which can place them on a less favorable part of the length-tension curve for hip extension; when the knee is flexed, their length across the knee changes, altering the hip-extensor capacity. So yes, they are a two-joint group, and their hip function is influenced by knee position.