Anatomy Lesson: The Knee

Time for another installment of Anatomy Lessons.  Last week we went over the Foot/Ankle, now we're moving up the chain to the knee.  When you think about the knee in sports, the first thing that pops into most heads is injury; and not just a little ding but season ending injuries.

The knee is susceptible to injury because of the nature of certain sports, and the because the knee is often left helplessly to follow the hip and/or left to compensate for the foot/ankle.  The knee is stuck between two joints who often leave crap behind, and the knee is forced to take much of that crap. 

"The knee is a dumb joint, the foot/ankle and hip dictate not only the position of the knee, but what it's capable of doing as well". - Mike Robertson

So while the knee is often the joint that gets injured, it's usually a result of problems seen elsewhere in the body.  But for now let's find out the nitty gritty of the knee!

Bones: Four bones make up the knee joint.

• Tibia - Shin bone
• Fibula - Smaller lower leg bone running parallel to the tibia
• Femur - Thigh bone
• Patella - Knee cap

Muscles: 

• Quadriceps - The quads are the group of muscles on the front side of your thigh.  The quad group is made up of 4 muscles - rectus femoris, vastus lateralis, vastus medialis, vastus intermedius. The quads work to extend the knee joint as well as provide stabilization.  
• Hamstrings - The hamstrings are the group of muscles on the backside of your thigh.  The hammy group is comprised of 3 muscles, biceps femoris, semitendinosus, semimembranosus.  The hamstrings work to flex the knee joint as well as provide stabalization.
• Popliteus - This muscle runs on the backside of the knee joint.  It is often thought to unlock the knee from extension during walking/running.  The popliteus assists in flexion, but also provides a rotational component to the knee.  It will rotate the tibia and femur inward during certain situations or positions. 
• Lower Leg - We're bunching these all into 1 group for simplicity sake.  The calves (gastrocnemius and soleus) and tibialis anterior also have some influence on the knee.  Aiding in flexion and extension respectively, but far far less in comparison to the quads and hammies. 

Ligaments: Ligaments connect bone to bone. They are key in stabilization of the knee

• Medial Collateral Ligament (MCL) - The MCL runs on the inside (medial) aspect knee attaching to the femur and tibia.  It prevents excessive inward movements or valgus forces.  A typical injury to the MCL will be caused by a force acting on the outside of the knee, forcing the knee inward.
• Lateral Collateral Ligament (LCL) - The LCL runs on the outside (lateral) aspect knee attaching to the femur and fibula.  It prevents excessive outward movements or varus forces.  A typical injury to the LCL occurs when a force occurs on the inside of the knee, forcing the knee outward.
• Posterior Cruciate Ligament (PCL) - The PCL is the strongest ligament in the knee, and is deep inside the knee joint behind the ACL.  Cruciate ligaments cross in the middle of the knee joint, and the PCL travels from the posterior surface of the tibia to the anterior surface of the femur.  It prevents backward motion of the knee.
• Anterior Cruciate Ligament (ACL) - The most well known, and "infamous" knee joint.  The ACL runs from the anterior surface of the tibia, to the posterior surface of the femur.  It prevents the tibia of moving forward.  Injury to the ACL is severe and can cause a recovery period of 9-15 months. 

Cartilage/Tendons: Cartilage is a connective tissue that cover the ends of the knee joint bones to help bones more freely against each other.  Tendons attach muscle to bone.

• Menisci - The lateral and medial menisci attach to the tibia on the respective outside or inside portions of the knee.  These menisci act as shock absorbers and help distribute forces evenly through the knee.  Menisci also aid in keeping the knee stable.
• Articular Cartilage (AC) - Articular cartilage is on the ends of all bones, in any joint.  So in the knee joint, AC covers the ends of the femur, tibia, and back of the patella.  AC is lubricated by synovial fluid, synovial fluid and AC create a slippery, lubricant that is 3 times more slippery than ice and even more impressive, 5 times more slippery than the road runner is to the coyote.  This combination allows the bones to move against each other freely and without pain or resistance. 
• Quadriceps Tendon - Connects the quad muscle to the patella.  It helps assist in knee extension and provides stability of the patella. 
• Patella Tendon/Ligament - The patella tendon connects the patella to the tibia, so in reality it is a ligament, but most people know it at as the patella tendon.  The patella tendon assists in knee extension and works to keep the patella stable

Common Issues

Stability + Mobility - In the joint-by-joint theory it is stated that the knee joint prefers and needs stability.  The knee is often thought as a hinge joint, with only flexion and extension movement, but the knee does have rotational components.  So while the knee does lean towards needing stability, it also needs adequate mobility. 
We definitely want to see full extension from the knee joint - a quick easy test for this is to sit on the ground with your legs extended flat.  From there, extend your knee and see if you can get your heel to come off the ground - without flexing your hip!  Essentially seeing if you can go beyond 180 degrees of extension or not.  If you can't then you A. lack knee extension ROM and/or B. lack some quad/extension strength.  Both are very important for knee health.

Stuck in the Middle - The knee is between the hip and ankle joints, and often receives the brunt of bad news if these two joints are not working optimally.  The knee often just follows suit with what occurs up at the hips.  The knee is in a position that forces it to just follow the path set by the hips and pelvis.  So while the knee may be perfectly happy and healthy, it can get pulled down by problems at the hip or ankle.

Ligament Injuries - We all know the horrible effects that a ACL or some other kind of ligament injury can have.  During a surveillance study on 100 high school from 2005-2001

• 15% of all athletic injuries were knee injuries
• Half of these knee injuries were ligamentous
• MCL was the most common injury
• Over 21% of all knee injuries were treated with injury
• Occurrence rate were higher for games than practice
• Occurrence rate for females was higher than male

Many of these are contact type injuries, where avoidance is hard to prevent.  On the other hand, we also see many non-contact ligament injuries, and these can be prevented.  Many will say these occur from an "un-stable" knee, but this is far to simplistic. The occurrence of a knee actually being "un-stable" or lax is not very common. This "un-stableness" is more likely a result of weakness or lack of mobility at the hip, ankle, or surrounding muscles. Training or continuing to allow poor knee mechanics, even if they are rooted elsewhere, is a major No-No. 

Valgus Knee Collapse - Valgus knee collapse is the term given the knees "buckle" inwards.  This collapse is a break in proper knee mechanics and puts a ton of stress on the knee joint and has been associated with MCL and ACL injuries, patellofemoral pain, IT band pain, and tibial stress fractures.  This is seen in so many athletes, and work to correct valgus knee collapse needs to be essential in injury prevention and sport performance programs.

Fixes

Hip/Pelvis Strength - Like we touched upon, the knee is often helpless to the actions and control of the hip/pelvis.  If the hip and pelvis is strong and stable and gives a good path, the knee will follow.  But if the they are weak and present a poor path, the knees can't really help but follow.  This is when bad things occur.  The knee often will see great benefits from better strength and control of the pelvis/hip and work targeted to the glute max, glute medius, diaphragm, core, hip rotators, psoas, and QL.

Ankle Mobility - Like we touched upon in the Foot/Ankle Anatomy Lesson, problems in ROM at the foot/ankle will often lead to compensations at the knee.  This might contribute to a valgus knee, or a tibial torsion, or some other compensations at the knee.

Strengthen the Quads and Hamstrings - Adequate strength and balance between the quads and hamstrings help influence stability, control, and distribution of forces among the knee.  Weakness or an imbalance between the quads and hams can alter the stability and control of the knee in certain directions or actions.  This can increase the stress seen in certain parts of the knee and over time this can add up, and lead to injury or altered mechanics.

Motor Control - Proper knee mechanics and tracking need to be taught.  Often times valgus or other compensations occur because the person is lazy or just developed poor motor control.  With young people, often just telling them to correct their mechanics is all that is needed.  They just need to know the proper technique. 

When looking at the knee from the side view, you should see the hip, knee, and ankle in a single line.  Next view from the front, it should show a relatively stacked position of the hip, knee, and ankle as well.  Depending on body types (more the case with females) you might have a natural medial alignment of the knee in comparison to the hip, but ideally the closer to stacked the better. This alignment is a great start in improving knee function and health. 

Knee ROM - Despite the tendency for the knee to be stable, we also need to make sure it has adequate ROM.  In flexion, you should be able to get your heel to your butt.  If you cannot then you are leaving performance potential on the table, as many track and field coaches have stated that if one cannot cycle their leg through close to thier butt, they will not run at their full potential.
Along with knee flexion, we need to see full extension, past 180 degrees.  Lack of extension is a major cause of concern for future dysfunction.  Check these out by KStarr and get it fixed!

Conclusion

If you take away one thing from this today, it's that problems at the knee are usually rooted elsewhere.  Whether that be the hips or ankle or pelvis or spine.  Don't always think a knee injury or problem is directly caused by the knee, mostly it's rooted elsewhere.  The knee is a conformist, it just follows what other body parts are doing.  Fix them and make them all cool and dandy, and the knee will follow suit and become part of the cool crowd. 

Well that's all we got for you today.  Hope you enjoyed, if you did be sure to sign-up for BBA updates to keep up with us here at BBA.  Until next time Go Get 'Em!


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