Exercise guide
Knee - Extension
- Intermediate
- Isolation
- Timed hold
- Lower legs
- Upper legs
This isolation exercise targets the quadriceps, specifically the vastus medialis, to improve knee stability and terminal extension strength. It is an excellent low-impact movement for knee health and muscle activation using only a step for elevation.
Reviewed by the Crucible Fit team · Updated June 2026
Muscles worked
Setup
- Sit on the edge of a high step or bench so your feet hang freely without touching the floor.
- Place your hands on the sides of the step to stabilize your torso.
- Keep your back straight and your core lightly engaged to maintain an upright posture.
- Position the back of your working knee firmly against the edge of the step.
How to do it
- Exhale as you slowly straighten your leg by contracting your quadriceps until the knee is fully extended.
- Hold the peak contraction for one second, squeezing the thigh muscle as hard as possible.
- Inhale as you slowly lower your foot back to the starting position using a controlled 3-second tempo.
- Complete the desired number of repetitions on one leg before switching to the other side.
Form checklist
- Keep the torso stationary; avoid leaning back to swing the leg up.
- Ensure the movement occurs strictly at the knee joint without hip involvement.
- Flex your toes toward your shin (dorsiflexion) to maximize tension in the quadriceps.
- Maintain a smooth, fluid motion without using momentum at the bottom of the rep.
Pro tips
- To emphasize the vastus medialis (the 'teardrop' muscle), slightly rotate your toes outward at the top of the extension.
- Focus on the mind-muscle connection by visualizing the quadriceps shortening as you lift the weight of your lower leg.
Make it harder
- Pause for 3-5 seconds at the top of each rep to increase time under tension.
- Perform the exercise with a slow 4-second eccentric (lowering) phase to challenge muscle control.
Frequently asked
- What muscles does the knee - extension work?
- The knee - extension primarily targets the quadriceps, and also works the glutes as secondary muscles.
- What equipment do you need for the knee - extension?
- The knee - extension requires no equipment — just your body weight.
- Is the knee - extension good for beginners?
- The knee - extension is rated intermediate. Build a base with simpler variations first, then progress to it with light load and strict form.