Why do we need a straight knee?
This is not medical advice.
This is a problem that really needs to be addressed by professionals in person. This article is just a review to understand why it might be necessary.
We need a straight knee when we are walking. When we walk, and plant our heel, the knee is mostly straight. As momentum carries us forward, we vault over a straight knee. This is more efficient than having a bent knee. Our leg muscles have to work much harder if we have a bent knee, and we might have pain with every step.
When do we have a bent knee when walking?
I usually see this after someone has had a knee injury or surgery. The knee becomes stiff as part of the normal healing process. Inflammation brings some stiffness, and scar tissue starts to set it.
Sometimes people have a meniscus tear or cartilage damage that is more of a mechanical reason that they are unable to straighten their knee. This is more difficult.
This is also a habit forming problem due to pain, and sometimes requires conscious retraining with every step to reverse.
This problem is best watched and progressed earlier than later. Once scar tissue and habits set in, this is extremely difficult to reverse, and it’s more painful to address it later.
Exercises to fix the problem
There are usually two problems.
Passive
There is a passive restriction, meaning the joint is stiff and unable to straighten.
This picture shown helps address this stiffness. Usually people place a weight on their knee for a gravity stretch. The weight should not be so heavy that the muscles can’t relax, yet not too light where no stretch is felt. For most people this is in the 2-4 pound range, 3-5 sets of 30 seconds, 2x/day.
Active
The quadricep muscles are unable to straighten the knee, due to weakness, poor leverage, or in combination with the first issue. This exercises helps the quadricep get stronger and push the knee straight. Sometimes the body will cheat by pushing with the hips backwards. Emphasis needs to be at the knee joint.
Do we need a straight knee in nature?
If you watch an indigenous person walk in the jungle, or you are walking barefoot in nature, do you plant your heel on the ground, and straighten the knee? Unlikely, as that would probably hurt more to plant our heel on rocks and roots.
I am guessing most of us would walk on the ball of the foot, which transfers impact force of walking to soft tissues and muscles, instead of our bones.
Planting our heels with a straight knee when walking and running transfers force of impact to our bones. Is this what causes increased likelihood of joint pain and osteoarthritis? Diet is likely also a factor.
Just curious about this and can’t prove it. I am unlikely to walk barefoot at work, yet walking on concrete and asphalt is probably not part of our original design.