Name of test

Knee extension

What it tests

knee extension, active and passive, tests the range of motion and the ability of the extensor mechanism to extend

How to do it

  • have the patient lie supine
  • lift the leg off the table, by holding on to the patient’s ankle. assess passive motion
  • have the patient sit up, and ask him or her to straighten the leg. that assesses active motion
  • passive motion can also be assessed with having the patient lie prone with the thighs at the end of the table, knees hanging off. gravity will extend the knee joint and the height difference between the feet can be used to quantify the loss of motion

The normal response

the patient should be able to fully extend, symmetrically with the other side

What it means if not normal

  • if the knee does not fully extend passively, a flexion contracture is present
  • if the knee does extend passively but not actively, an extensor lag is present
  • if there is no active extension at all, the extensor mechanism is damaged (quad, patella, patellar tendon)


an ability to fully extend the knee may reflect patello-femoral joint pain (see patellar inhibition)


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