What is the Knee Extension?

Elderly man kneeling on the sand knee strengthening Knee Extension


The knee extension is an isolation exercise that targets the quadriceps by extending the knees against resistance from a bent position.


  • Sit with back supported, knees bent 90 degrees. Straighten one knee using the quad muscles against resistance then control return to bent.
  • Perform 2-4 sets of 10-20 reps with both legs independently. Cables, machines, bands or dumbbells can provide resistance.
  • Full range of motion is crucial – keep knees bent as far as comfortable without strain then fully extend.
  • Knee extensions strengthen quads but are easier on the knees than squats. They help balance leg training.


  • Seated knee extension machine
  • Banded kneeling knee extension
  • Cable knee extension

Related Terms

  • Quadriceps, leg extensions, open vs. closed kinetic chain

Common Questions

  • Are knee extensions bad for your knees? No if using proper form – they can benefit knee health.
  • Should I do partial reps? Partial reps near full extension can isolate quad muscles, but perform full range too.

Do Not Confuse With

  • Leg press – Compound quad exercise that also involves the knees.
  • Leg raises – Abs exercise lying on back and lifting legs up.
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