Which muscle primarily extends the leg?

The vastus lateralis is the primary muscle responsible for extending the leg, particularly at the knee joint. This muscle is one of the four components of the quadriceps femoris group, which is crucial for activities that involve straightening the leg, such as walking, running, and jumping. The vastus lateralis is situated on the lateral side of the thigh, and when it contracts, it pulls on the patella (knee cap), leading to the extension of the leg.

Understanding the role of the vastus lateralis in leg extension highlights its importance in lower body strength and functionality. This muscle works in concert with the other quadriceps muscles—vastus medialis, vastus intermedius, and rectus femoris—to facilitate smooth and powerful extension of the knee, which is critical for athletic performance and overall mobility.