The quads are least efficient in their inner range partially due to the concept of active insufficiency and partially due to reduced mechanical advantage at terminal 20° of knee extension. It’s quite easy to appreciate the loss of strength in the final 20° of knee extension when you try a knee extension machine at the gym. As PTs we can also appreciate the quads lag on our patients post ACL repair or TKA.
I propose that MOST individuals with hip & knee symptoms have a “quads lag” to some degree …but it is simply not visible.
My patients have benefitted when I have prescribed the following closed kinetic chain quad exercise. The beauty of this exercise is that it is most often comfortable to do even in those with PFPS or knee OA who may have reported of pain with other strengthening exercises.
Step 1: Loop a “Superband” or “Strength Band” (available at Fitness stores for $20) around a sturdy structure such as a bedpost.
Step 2: Place the other loop of the band behind the knee while in a lunge position. Step back until there is significant tension on the band.
Step 3: Push the popliteal fossa back into the band and FULLY extend the knee as if stepping up on a step. Hold the strong quad contraction for a few seconds and very slowly release.
Step 4: Repeat as many reps or sets as needed until fatigue …which is inevitable.