The vastus lateralis is primarily responsible for knee extension, which is vital for movements such as walking, running, and jumping. When the muscle contracts, it pulls on the patellar tendon, which moves the kneecap and consequently straightens the leg. This function is not only critical during dynamic activities but also during static positions, as it helps stabilize the knee joint, ensuring proper alignment and distributing forces effectively during weight-bearing activities. The vastus lateralis also assists in providing support to the hip joint and contributes to overall lower limb function, allowing for efficiency in movements and reduction of injury risk.