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Full Knee Hyperextension and Quad Lag after ACL reconstruction

acl knee extension

Full knee hyperextension equal to the contralateral side is essential after ACL reconstruction. or any post-operative knee.

I know most of you are already looking at this post-operatively and are doing this very well, but we still see this missed quite frequently. We find that if there is pain or difficulty transitioning as we get to higher levels of rehabilitation, it's usually a missed impairment like achieving full hyperextension equal to the opposite knee.

I find the best way to look at knee hyperextension range of motion is a dense towel roll, and I want to get that to the height on the uninvolved leg, that when they do a quad set, I can barely get my hand underneath their knee (a finger width distance so the back of my fingers touch the back of the knee and the palmar side of my fingers are flat on the table).

I do a gross measurement at this point -  when she tightens up on the uninvolved side, I can get to about my DIP.  When I get under the post-operative side, I can get my full hand under here. That is a substantial difference between the right and left side. Certainly, you can measure that with a goniometer, but the error of the goniometer doesn't allow us to identify the subtle differences in knee hyperextension. 

The other subtle problem that I see a lot, particularly post-operatively is a quad lag and a subtle quad lag being reinforced. And that poor pattern can be detrimental to the rehabilitation process. In the above video we have her come up onto her elbows here for her straight leg raise, tighten up that quad and lift up. It's that subtle usually, where it's just this little bit of lag there, where they're not keeping that knee fully hyperextended. 

Subtle hyperextension is really important to catch. If we don't catch that, we're going to be reinforcing motor programs that are really not ideal . . . that they're not going to get their full extension and may never because of that.

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