Which muscle is primarily responsible for knee extension?

Which muscle is primarily responsible for knee extension?

• A. Biceps Femoris short head
• B. Adductor longus
• C. Vastus lateralis
• D. Adductor magnus

Answer: (C)

Knee extension is produced by the quadriceps femoris group, which straightens the knee by pulling on the patella and transmitting force through the patellar ligament to the tibia. Among the options, the vastus lateralis is a major component of that group and sits on the lateral side of the thigh; its fibers contribute directly to extending the knee and also help stabilize the patella laterally during extension. The other muscles listed are not primary knee extensors: the biceps femoris short head flexes the knee, while adductor longus and adductor magnus mainly act on the hip (with the latter having a hamstring portion that affects hip movement rather than knee extension). Thus, vastus lateralis best fits the role of knee extension.

Knee extension is produced by the quadriceps femoris group, which straightens the knee by pulling on the patella and transmitting force through the patellar ligament to the tibia. Among the options, the vastus lateralis is a major component of that group and sits on the lateral side of the thigh; its fibers contribute directly to extending the knee and also help stabilize the patella laterally during extension. The other muscles listed are not primary knee extensors: the biceps femoris short head flexes the knee, while adductor longus and adductor magnus mainly act on the hip (with the latter having a hamstring portion that affects hip movement rather than knee extension). Thus, vastus lateralis best fits the role of knee extension.