All About The Knee

by Ryan
Andrews
, October 18th, 2010.

To keep healthy knees, you need:
  1. Mobile joints above and below the knee
  2. A strong knee joint
  3. Proper mechanics during physical movement
That about sums it up.
bobs trick knee endless source frustration

What is the knee?

The femur, tibia, and patella come together to form the knee joint. The width
of the knee joint allows the structure to handle greater loads.
knee joint anatomy
The patella is your “kneecap” and sits within the quadriceps tendon,
providing an enhanced mechanical advantage when the quads are contracted. The
back side of the patella is a smooth surface made up of hyaline cartilage. This
is important during knee movements: flexion, extension, and rotation.

The knee ligaments, capsule and menisci help to keep your knee joint
together.

The value of exercise

Our bodies respond to the stresses that we place on them. If you exercise
regularly, you inspire turnover and growth of knee structures (muscles and
connective tissue). This is a good thing. To keep the knee joint healthy, you
need to balance exercise loading, frequency, activity type, and
rest/recovery.
Loading Frequency Activity type & variety Rest & recovery Result
Too intense Too often; irregular Not enough variation Not enough Overuse injuries, inflammation, injury
Just right Regular and consistent Varied; well-balanced Adequate; active recovery Healthy knees
Too low Rare; irregular Minimal activity Too much Weak, injury-prone ligaments
For instance, if you keep pounding out the hard miles doing only distance
running every day, you’ll probably end up with tendonitis. On the other hand, if
you sit around all day, you’ll also risk knee injury from weakened knee
structures and the pressure of the kneecap on the thighbone in the seated
position (aka “movie theatre knee”).
For healthy knees, get regular daily activity, keep the joint moving through
a full range of motion, and do different things.

Knee ligament anatomy

Knee Ligament
Anatomy Animation

Four main ligaments provide stability and prevent excessive movement of the
knee.
  1. Anterior cruciate ligament (ACL) – prevents the tibia from moving forward
  2. Posterior cruciate ligament (PCL) – prevents the tibia from moving backward
  3. Medial collateral ligament (MCL) – prevents excessive inward movement of the
    knee joint. This is the most commonly injured knee ligament, but it can usually
    heal without surgical intervention.
  4. Lateral collateral ligament (LCL) – prevents excessive outward movement of
    the knee joint
Knee ligaments are tiny. The ACL and PCL are only 6-14 millimeters wide.
Two crescent- shaped rings of cartilage comprise the menisci. The menisci
provide knee stability, distribute weight from the femur to the tibia, act as
shock absorbers, and spread synovial fluid. Just like other types of cartilage,
they can be torn.
cross sectional knee anatomy
It’s not just ligaments that keep our knee intact. The quadriceps, hamstrings
and calves enhance stability too. When these muscles are strong, we are able to
rely less on the passive structures, like ligaments, to resist unwanted
movement.

What you should know about the knee

Most knee problems develop over time, not just on a random day in your
basement during a dance-a-thon. This is repetitive trauma (think: wear and
tear), and any mechanical device (including the knee) will fail with excessive
strain. One in three sports-related injuries occurs at the knee.

Warming up and dynamic joint mobility

Warming up and dynamic joint
mobility
seem to be important for knee health. These practices help to
control inflammation, distribute joint fluid, develop structures around the
joint, and enhance range of motion.

Resistance training

Resistance training through a full (and mechanically correct) range of motion
is essential for healthy knees. Weight-bearing exercises can help to promote
joint stability and strength.
However, poor technique (including going too heavy in a partial range of
motion) and too-heavy or too-frequent resistance training without adequate
recovery can damage the knee joint. Don’t keep hammering away at those squat
one-rep-maxes too often — mix up the movements and the loading.
And remember that your legs move in more than one plane! Try asymmetrical and
one-legged movements such as:
  • “star” lunges or jumps (stepping/jumping out to the side or on a diagonal)
  • stagger-stance squats, wrestling shoots
  • side/diagonal step-ups on to platforms
  • zig-zag jumps and runs, etc.

Common knee problems

Patellar tendonitis
Get ready for this knowledge bomb: Tendonitis is
the inflammation of a tendon. Who knew? This often takes place with repeated
stress and loading (translation: overuse). Ice, adequate recovery between
workouts, and developing mobility can help. You can reduce discomfort by
limiting the range of motion during exercises, but ideally you want to work your
way back to a full,  healthy range. You can also use static holds and eccentric
training.
Chondromalacia patella/kneecap pain
You’ll often notice this with climbing stairs,
walking down hills, or sitting. This is the progressive destruction of hyaline
cartilage on the backside of the kneecap. You might hear snapping, popping and
cracking noises when you bend your knee. Perfect technique on lower body
exercises and reducing the range of motion (with the eventual aim of increasing
that ROM) can help. Women tend to suffer from this condition more than men.
Torn meniscus/removal of meniscus
Meniscus problems often manifest as a catching or
grinding sensation in the knee. Since a meniscal injury can cause pain, catching
and swelling, many people opt for surgery to remove torn bits. Menisci lack
blood supply except at their outer rim, so they often heal poorly when torn.
Heavy vertical compressive loads (e.g. heavy squatting, jumping) can interfere
with healing. Use a limited, gradually increasing range of motion and minimal
resistance while recovering.

Ligament problems

ACL injuries are common in sports with running and
jumping, such as basketball and soccer, or with twisting/lateral forces on the
knee, such as downhill skiing. Women suffer ACL injuries more than men because
their knee joints tend to be looser; however, learning and practicing proper
running and jumping form can greatly reduce the risk.
ACL repair is a biggie, since it cannot simply be
sewn together after it tears (try attaching two mop ends). Rather, ACLs are
reconstructed with borrowed tendons.
It may be months before progressive resistance
training can be re-introduced after an ACL repair. Rehab for ligament injuries
often involves partial range of motion exercises and hip/hamstring
strengthening. While open chain exercises might serve a purpose in limited rehab
settings, use is reserved until post-operative knee function is assessed.
Mild sprains can occur when a ligament is
overstretched or partially torn and recovery consists of rest and ice. Workouts
resume when tolerated once the knee feels better.
Arthritis
While breakdown and inflammation of knee joint
cartilage can take place with advancing age, it doesn’t mean pain and disability
soon follow.
The elephant in the room with most arthritis is
body weight. A higher body weight is strongly associated with knee arthritis. If
your BMI is above 30, chances of developing arthritis go up nearly 4 times. More
body mass requires more plantar flexion and a shorter stride. This leads to
hamstring dominant knee stability. Not good. An abnormal positioning of the feet
during walking and running is also common in those who carry extra pounds. The
toes can rotate out (duck walk) or in (knock-knee, aka valgus), both of which
can cause knee injury and diminished mobility.

What to do for knee health

Check your shoes and how you walk

A non-bouncy and relatively flat shoe sole can assist in balance and
integrity around the foot and ankle. There is emerging interest in
barefoot/minimally shod walking — the theory is that the more sensory input
comes through the soles of the feet, the more the body can perceive and correct
deviations in position.
Messed up shoes, feet and ankles can lead to messed up knees. In fact, too
much cushioning in a shoe could be a problem; it’s harder to stabilize feet in
squishy shoes.
“Duck feet” or the opposite, “knock knees” and excessive heel strike when
walking/running can cause knee problems.

Check your squat

Learn good squat technique and use it. Don’t sacrifice good technique for
adding more weight, especially in a partial range of motion.
Keep your hips behind your heels — sit back into the squat. The farther
forward the knees, the greater the force on the knee joint. The goal is to keep
shins closer to vertical, although Olympic weightlifters tend to squat with a
slightly greater shin angle.
Good squat form
cavemansquatting
Yes, we evolved to do full squats.
aimee-high-bar-squat
Good squat
form
Squatting with a serious forward shin lean (aka the “campfire squat”) can be
safely done unweighted, but it puts a lot more stress on the knee joint — we
don’t recommend you try it with heavy weight.
Not-so-good squat form
10054203 Campfire Cwby
Free weight squatting seems to activate muscles around the knee more than
machine squats.
The back squat results in higher compressive forces at the knee joint,
compared to the front squat.
Squatting on a decline or with something under your heels maximizes load on
the patellar tendon and minimizes glute recruitment.
Back squat Front squat
6a00d8341bf90553ef01157069d026970c-800wi crossfit-colin-front-squat
Squat with heel
elevation

6a00d8341bf90553ef01310f9e9fdc970c-800wi
Just plain
awesome

6a00e5509c89fc883401127978403128a4-800wi
A wide stance and greater range of motion when squatting can elicit more hip
musculature. If you squat wide, you’ll probably find it most comfortable to turn
the toes out slightly — be sure that your knees are following the direction of
your toes, and don’t let the knees cave in.
6a00e54edabd83883300e54f7727268833-800wi
Going down to where hamstrings contact the calves (rather than stopping and
reversing direction at parallel) seems to be the safest position for knees
during weighted squats. This will need to be adjusted based on length of femur,
tibia, and torso. Once the lower back starts to lose its lordotic curve, you are
likely going too deep.

Check your muscle balance

Many physios say that the knee is the “outlet valve” for the hip. Knee
problems may actually be hip problems.
Most people have stronger quads than hams and glutes, making knee stability
unbalanced. Counteract this with strong hips. Strengthening the hips two times
per week for six weeks reduced patellofemoral pain for one group of athletes.
The following exercises can strengthen the hips:
Hip Bridge
Dumbbell Step-Up, Alternating
Single-Leg Stiff-Leg Deadlift, Weighted
X-band
walks

Band
stomp

But don’t completely neglect the quads. Weak quads can lead to an unstable
knee joint. And an unstable knee joint can lead to weak quads. It’s a vicious
cycle. The vastus medialis obliquus (VMO) is a key knee stabilizer.
vmo
Activating the VMO can be tricky. Try terminal knee extensions (TKEs) and
backwards walking (even better on an incline) to start.

After you
master TKEs and backwards walking, full range of motion squats and single leg
exercises can help develop the VMO (well, when proper form is used).
Activating the muscles surrounding the knee can be tough with a wider
Q-angle. The Q-angle is the relative angle between the hip and knee, and
problems can arise when it’s larger (i.e. the femur has more of a tilt). This is
one of the reasons why female athletes — who have wider pelvises than male
athletes — are more likely to suffer an ACL injury.
q-angle-female-male

Check your flexibility/mobility

We need mobile joints and soft tissues around the knee to accommodate enough
movement.
In your life you’ll have a personal standard for knee flexibility depending
on what you do (professional chess player vs. collegiate pole vaulter). But if
you can’t do a full squat, you probably have limited mobility.
Joint mobility can be good, but we don’t want excessive joint mobility at the
knee joint itself. However, limited mobility can affect proper range of motion,
which alters knee mechanics. Thus, we want a balance between mobility/movement
and stabilization.
We can improve the knee’s range of motion with flexibility exercises and
building mobility at surrounding joints. (See All About Dynamic Joint Mobility.)
Conversely, we reduce the knee’s range of motion by being inactive — especially
if we sit all day, which shortens the front of the hips and “turns off” the
muscular contribution from hips. This alters hip mobility and the knees pick up
the slack.
Improving hip mobility is one of the most crucial things you can do to
improve knee health. Stretches for the hip flexors:
Lunge with knee
on pad

Mermaid/one
legged king pigeon
(advanced)
Anterior/posterior leg swings
Warrior lunge
with reach

Side to side leg
swings

Bow pose
Back dome
(starts at 2:00 in video – no resistance)
Don’t neglect ankle mobility either. Like the hips, the feet/ankles can
affect the kinetic chain. Flexibility exercises for the ankle:
Wall knee
taps

Elevated ankle
stretch

Foam rolling for the tibialis anterior (about ¾ down the
page)

Summary and recommendations

Healthy knees require…
…mobile joints above and below the knee.
  • Work on hip and ankle mobility exercises.
…a strong knee joint.
  • Do full range squatting movements.
  • Train the quads, making sure to activate the VMO.
…a strong posterior chain.
  • Train your hips, hamstrings, and glutes.
  • Include single-leg work.
Don't forget that posterior chain!
Don’t forget that posterior chain!
…proper mechanics during physical movement.
  • If it hurts your knee, avoid it (but work on your underlying biomechanics
    and solving the fundamental problems).
  • Check your gait and shoes.
  • Learn and practice proper running, jumping, and exercise form.
In general, if your knees are already in pain, the rules of exercise
modification include decreasing the resistance, adjusting the range of motion,
controlling the speed, reducing the volume of work, and/or changing
exercises.
For healthy knees, get regular daily activity, keep the joint moving through
a full range of motion, and do different things.

Extra credit

Closed chain exercises can reduce the anterior directed forces acting on the
tibia in relation to the femur, increase compressive forces between the tibia
and femur, increase co-contraction of the hamstrings and quads, mimic daily
functional activities more closely, and reduce the incidence of patellofemoral
complications. (Translation: training real-world movements like squatting and
walking uphill puts the correct forces on the knee, recruit the right muscles,
and keep your knees happy.)
Proprioception helps to protect the knee from injury and joint damage.
Develop proprioception by doing single-leg lower body exercises, wearing a knee
sleeve (for additional sensory input) or standing on one leg while you brush
your teeth and floss.
Forces on the knee can range from about twice your body weight during normal
walking, to more than four times your body weight during running and jumping
activities.
Knee wraps and sleeves can help to promote warmth and blood flow at the
joint, as well as provide proprioceptive cues. However, taping and loosely
wrapping the knees will not provide much stability, so don’t rely on this.
Heat applied to the knees pre-workout can help make tissues more elastic.
Be careful with plyometrics if you’re overweight or your knee is injured.

Further resources

Nick Tumminello’s Joint Friendly Strength Training DVD
Big legs with bad knees
Mike Robertson’s Knee Basics Part 1Part 2Part 3

References

Schwanbeck S, Chilibeck PD, Binsted G. A comparison of free weight squat to
Smith machine squat using electromyography. J Strength Cond Res.
2009;23:2588-2591.
Gullett JC, et al. A biomechanical comparison of back and front squats in
healthy trained individuals. J Strength Cond Res. 2009;23:284-292.
Paoli A, Marcolin G, Petrone N. The effect of stance width on the
electromyographical activity of eight superficial thigh muscles during back
squat with different bar loads. J Strength Cond Res. 2009;23:246-250.
Caterisano A, et al. The effect of back squat depth on the EMG activity of 4
superficial hip and thigh muscles. J Strength Cond Res. 2002;16:428-432.
Escamilla RF. Knee biomechanics of the dynamic squat. Med Sci Spots Exerc.
2001;33:127-141.
Senter C, Hame SL. Biomechanical analysis of tibial torque and knee flexion
angle: implications for understanding knee injury. Sports Med.
2006;36:635-641.
Robertson M. Bulletproof Knees. 2007.
Shankman G. Training guidelines for strengthening the injured knee: Basic
concepts for the strength coach. NSCA Journal 1989:11:32-42.
Johnson J. Treat your own knees. Hunter House Publishers. 2003.
Messier SP. Obesity and osteoarthritis: disease genesis and nonpharmacologic
weight management. Rheum Dis Clin North Am 2008;34:713-729.
O’Neill DF. Knee Surgery: The essential guide to total knee recovery. St.
Martin’s Press. 2008.
Garrett J & Reznik B. Knee pain: The self-help guide. New Harbinger
Publications. 2000.
Fleming BC, Oksendahl H, Beynnon BD. Open- or closed-kinetic chain exercises
after anterior cruciate ligament reconstruction? Exerc Sport Sci Rev
2005;33:134-140.
Visnes H & Bahr R. The evolution of eccentric training as treatment for
patellar tendinopathy (jumper’s knee): a critical review of exercise programmes.
Br J Sports Med 2007;41:217-223.
Dierks T. Presentation – American College of Sports Medicine Annual Meeting,
2010.
Lange AK, Banvanseele B, Fiatarone Singh MA. Strength training for treatment
of osteoarthritis of the knee: A systematic review. Arthritis Rheum
2008;59:1488-1494.
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About dkpilates

Pilates Instructor, Yoga Instructor, Personnel trainer and Group Fitness Instructor. Don teaches Contemporary and the Authentic forms of Pilates, in the later 90's, Don began his study of Yoga. His study of Yoga includes the Hatha, Iyengar, Bikram, and Astanga disciplines. His other areas of interest in fitness include Martial Arts, Spin, Boot Camp Training, and Weight Training. Don has extensive training and certifications from AFFA, IDEA, MadDog, B-Fit and Polestar. Don Continues his of Pilates education with Michelle Larson in Santa Fe New Mexico. His personal philosophy related to fitness is to aid students in a personalized balance of strength, stamina and flexibility. He is dedicated to design a program specifically for his students independent of the season of their life to create functional movement and help them reach their fitness goals.
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