This week we dove into discussion of the knee joint, and why is desires STABILITY. Let’s revisit some of the points and concepts discussed, a go a little bit deeper.
It started with understanding a very important concept
EACH joint has ratios of inherent bony stability to soft tissue stability (or dynamic stability). Generally speaking, joints that have more bony stability crave mobility, and vis versa. So let’s take a look at the knee:
Essentially two relatively flat bones sitting atop each other. When you consider the extreme example of boney stability like the ball and socket of the hip (fun fact: 70% of femoral head contacts the hip joint), you can appreciate the decreased boney stability of the knee, THEREFORE, the knee depends on soft tissues and contractile structures (ie muscles) for STABILITY. While inherently BONEY joints with great stability crave mobility.
Something that always resonated with me was when I heard Charlie Weingroff talk about how “the knee is dumb.” What does that mean?
It means that in closed chain, we really cannot move the knee independently with out moving the hip and/or ankle. Whats that mean? Hip and ankle have HUGE implications on knee control (aka stability).
Putting it all together:
What makes most sense than, for a awesome daily exercise for knee stability? Something that combines hip/ ankle activation, as well as isometric contraction of muscles surrounding the knees (ie quads, hammies, adductors, calfs).
How about this classic:
SINGLE LEG STANCE IN SLIGHT HIP HINGE.
You can challenge your self by closing your eyes, or standing on an uneven surface. BUT, we spend roughly 60% of our gait cycle on one leg, so it would make sense to have good single leg control, right?
Try dosing this for 10-30 seconds once a day and go from there. Stable knees are healthy knees! See post below for example of what we want, and what we do not want.
If we continue on this notion of gaining knee stability through muscle activation. Let’s look at Teddy’s post on dynamic knee stability when it comes to reducing risk for ACL injury.
As we learned from this post, the ACL is most vulnerable during the first 20 degrees of knee flexion in closed chain (roughly). This is because as we get closer towards 20 degrees of flexion, it puts the knee in a “loose pack” position, thus allowing for tibial rotation which we know contributes to the holy grail of ACL injury mechanisms.
This means that we want to OWN knee dynamic stability throughout this range of 0-25 degrees in concentric, isometric, and eccentric fashion.
Teddy does a great job of demonstrating three exerises that target deceleration (or eccentric) training of the knee musculature to help better absorb force and control knee mechanics against mechanisms associated with ACL injury.
On the contrary, Joe was able to play devils advocate, and give us some excellent food for though on why we also might want to take a look at expressing tibial rotation. Let’s first understand the closed chain “Screw Home” Mechanism. It starts by understanding the anatomy of the Popliteus muscle. The Popliteus, as shown below, has origin on the lateral femoral condyle, and runs into the tibia obliquely directly above the SOLEAL LINE, and important landmark on the back of the Tibia. So we can see how in open chain, the Popliteus will rotate the Tibia internally relative to the Femur. On the other hand, in closed chain, the Popliteus will rotate the the Femur externally relative to the Tibia, “screwing it home” and locking the knee joint.
Regardless, we understand that the knee joint HAS to be able to express some rotational ability, and Joe hits the nail right on the head with this exercise.
Joe also notes that a lot of his patients will often lack Tibial internal rotation, so this drill can be excellent for establishing baseline Tibial IR. See drill below!
CONCLUSION
So what are the key takeaways?
-Knees are a very vulnerable joint in terms of lacking bony stability, therefore we need to train dynamic stability!
-We know that knees are especially vulnerable at 0-20 degrees of flexion, so training our muscles in that range can have huge implications on reducing potential risk of ACL injuries!
-Knees must be able to express rotation in order to properly screw home and lock for gait and running, when we don’t have that ability, we might run into potential issues and knee pain secondarily.
Image Links
- http://www.precisionnutrition.com/all-about-the-knee
- http://strengthcoachconcepts.com/articles/Single+Leg+Movement+and+The+Lateral+Sub-System/
- http://corewalking.com/knee-stuff-popliteus-muscle/
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