One Big Reason Your Knee Won’t Bend After Stroke
I am gratefully a member of lots of different Stroke groups online. One problem that I see folks bring up frequently is difficulty with “knee bending”. It is actually fairly common and folks will put loads of effort into trying to bend that knee any way they can. But, for most folks there is a key thing that they need to spend time on before they go straining away to bend the knee.
What is it you ask? I will tell you, but first let's look at how the knee (basically) works. It is a joint that bends and straightens. There are 2 large muscle groups that create that movement. The muscles on the front of your thigh (Quadriceps) straighten the knee. The muscles on the back of your thigh (Hamstrings) bend the knee.
Before your stroke your brain was sending signals to these muscles in a coordinated way. To make the knee bend, the brain sends signals to the Hamstrings, to straighten the knee the brain sends signals to the quadriceps. And, when one muscle group gets the signals dialed up, the opposite muscle group has the signal dialed down. So, straighten the knee= increased signal to quadriceps, decreased signal to hamstrings.
What happens for many stroke survivors who are having trouble bending their knee is that their injured brain is sending signals to the Quadriceps (straighteners) too much. THat signal doesn’t get dialed down or it may even get dialed up. Many times with effort, people over activate the knee straightener (and foot pointers). This happens even when the person intends to bend the knee!
Most people would refer to this as spasticity. However, I prefer to think of it as over activation of an unintended muscle group. So then, the treatment for this is to learn how to decrease the activation/signal your brain is sending to the Quadriceps and then work on increasing the signal to the hamstrings.
There are some simple things you can do for this.
Don’t work so hard! What I mean is, give less effort toward the knee bending. Many times, with increased effort to bend the knee, the knee straighteners turn on more. The general way I think of it is this- Our brains try to do the easy thing. It is easy to turn on the straighteners. So whenever you are working hard without success, the brain says “Hey! I know what I CAN do really easy- straighten that knee” so it just sends the “easy signals”. Therefore, when doing something that requires knee bending, I will have someone work at 10-25% effort toward that movement. Another cue that I give is to “let the leg go” (or “be a noodle” or “be easy”) and then try the knee bending activity.
You can practice “letting the knee straighteners go”. Sitting somewhere that your foot dangles without touching the floor, you straighten your knee with less than 100% effort, then let your foot fall like it is heavy - really practicing letting go.
When you work on knee bending- make it easy. For this I will make the surface that the foot is moving on low friction. I might use a furniture slider, a nylon “transfer” sheet, a paper plate, a skate or something with wheels, or orient the exercise where gravity helps the bending.
These are all concepts that I use with regular success to help people improve their ability to bend their knee. And, while it may seem counter intuitive to focus on the straightening of the knee as well, it is one of the key things that seems to hold people back when improving knee bending.
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