ATI Fundamentals 5 Practice Test 2026 - Free Fundamentals Exam Practice Questions and Study Guide

Movement at a joint is produced by the muscles that act as the primary movers, called agonists. For the knee, the main agonists are the quadriceps, which extend the knee, and the hamstrings, which flex the knee. The opposing muscles that resist or slow the movement are antagonists, while synergists assist the agonists or help stabilize the joint. Antigravity refers to muscles that help keep us upright against gravity, and skeletal describes the type of muscle tissue itself. So the group that moves the knee is best described as agonists.