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Archive for the ‘Knee Anatomy’ Category

The menisci act to disperse forces accross the joint surface to reduce point-specific pressures. If the menisci are injured, the knees suffer increased risk of osteoarthritis.

The knee joint is the junction of the femur (thigh bone) and the tibia (shin bone), with the patella (knee cap) resting in an anterior groove.  When the leg is loaded, weight travels down the thigh towards the knee, but before it hits the shin, the force is dispersed by two shock absorbers in the knee called the menisci.  The menisci are filled with fluid, and when loaded, they spread the force over a broader area to prevent point-specific loading.  Without the  menisci, isolated forces could lead to breakdown and could damage the cartilage in the knee, and eventually the bone surfaces themselves.

Unfortunately, the menisci are often injured.  More specifically, the medial meniscus is frequently damaged as part of the “terrible triad” (a simultaneous injury to the medial collateral ligament (MCL), the anterior cruciate ligament (ACL), and the medial meniscus).  Meniscal tears are particularly dangerous because the menisci have very little blood supply.  This means that it is difficult for your body to provide the nutrients necessary to heal the menisci, and so they recover very slowly.  This is also troublesome because it may permit serious harm without severe pain, so you may not be aware of the severity of your injury.  This lack of pain is often short-lived, since research published in the journal, Arthritis and Rheumatism demonstrates that meniscal injury often precedes damage to cartilage and then osteoarthritis.

Even painless meniscal injuries are nearly always accompanied by swelling, so do not assume that you are healthy if your swollen knees are painless.  Anything that cause s excessive swelling may be causing harm.  If you think you may be injured, consult your doctor immediately.  If you wait until you feel pain, you may already be waiting too long.



 

The knee joint is the connection between two bones, the femur (thigh bone) and the tibia (shin bone).  The femur has two adjacent “condyles”, which are rounded portions that extend down to the tibia.  The tibia has two slightly cup-shaped sockets which meet the femoral condyles.

In healthy knee alignment, the femoral condyles rest evenly on the tibia, and apply nearly even pressure to both sides.  There are two types of knee deformities with asymmetrical force distributions: varus and valgus deformities.  A valgus (knock-kneed) deformity is where the knees are closer together than normal.  Valgus is more common than varus, and often occurs in overweight individuals.  A valgus deformity leaves a gap between the femur and the tibia on the lateral side, and increases pressure on the condyles on the medial side.  A varus deformity is where the knees are farther apart than normal.  Varus knees leave gaps between the femur and tibia on the medial side, and increase pressure on the lateral condyles.

These deformities are fairly common and lead to asymmetrical degeneration of the cartilage in the knee.  This means that  an osteoarthritic knee in valgus would have extreme damage to the medial side of the knee, and milder effects on the lateral side.

A medial knee brace for osteoarthritis is a tested and reliable treatment for knee osteoarthritis.  It is especially effective on an individual with a mild valgus deformity, because they have increased stress on the medial compartment.



Doctor-Speak

October 13, 2012

My mother recently had her annual check-up.  She returned, horrified, with a list of words that her doctor had said regarding her mild knee pain.  He told her that:

“Your menisci appear to be intact, but I note mild ligamentous laxity in your MCL.  I also suspect degradation of the articular cartilage along the anterior aspect of your medial compartment.”

My terrified mother began planning her funeral.

In the spirit of her struggle, this post is designed to help you understand doctor-speak.  Their language does not need to be frightening.

For example:

Medial:  Towards the midline of the body.  Your big toe is medial to your pinky.

Lateral:  Away from the midline of the body.  Your arm is lateral to your torso.

Anterior:  Towards the front of the body.  Your nose is anterior to your ear.

Posterior:  Towards the back of the body.  Your heel is posterior to your toes.

Superior:  Towards the top of the body.  Your head is superior to your neck.

Inferior:  Towards the bottom of the body.  Your foot is inferior to your knee.

So next time your doctor uses these words, remember the directions that they describe.



OA and the Quadriceps

September 14, 2012

Quadriceps Musculature

The quadriceps is a muscle group in the front of the thigh.  It is composed of the vastus lateralis, vastus intermedius, vastus medialis, and the rectus femoris muscles.  The vastii connect the thigh bone to the knee-cap and shin bone.  The rectus femoris stretches from the pelvis to the shin.  The primary function of the quadriceps is to straighten the knee, but because of the rectus femoris’s origin on the pelvis, it can also bend the leg at the hip.  The quadriceps are often used with the foot on the ground but can fire when the leg kicks.  When the foot is on the ground the quadriceps will contract to control knee bending and leg straitening.  This means that the quadriceps are important in activities like climbing and descending stairs, and sitting down and getting up from a chair.

Because the quadriceps muscles cross the knee, when they contract, they increase forces on the joint.  This extra pressure can increase friction, which can put stress on cartilage.  This means that using the quadriceps can increase pain for individuals with osteoarthritis of the knee.  Tension in or spastic firing of the quadriceps can put prolonged stress on the inflamed joint.  Individuals with weak quadriceps hyper-extend their knees when they walk.  This promotes stability but is damaging to knee ligaments and the hamstring muscles.  This also dramatically increases the stress on the cartilage and bone in the front of the knee.

Excessive tension in the quadriceps may be treated with slow stretching.  Spasticity and quadriceps weakness have more rigorous treatments, often including bracing.  For quadriceps weakness, bracing is often implemented to support the knee and prevent hyper-extension.  More sophisticated braces provide that support only when the leg is supporting body weight, while other braces may lock the knee full-time.  Quadriceps strengthening exercises are often recommended for individuals with osteoarthritis of the knee in order to avoid the pathological gait associated with quadriceps weakness.

 

 



Knee Structure

August 14, 2012

Knee bones

When understanding knee osteoarthritis it is important to understand the overall bone structure. The knee is comprised of four major bones. Understanding how your body works, you can better understand ways to reduce knee pain and increase your exercise and stretching routines.

Patella: The patella is your kneecap, a flat triangular bone that moves as the leg moves. The patella is located on the front of the knee, protecting the knee joint.

Tibia: Commonly referred to as the shin bone, this bone is used to connect the knee and ankle. The tibia is the second largest bone in the body and does the majority of weight bearing during movement.

Femur: Also know as the thigh bone. The femur is the longest bone in the human body. This bone runs from your knee to your hip joint, connecting your leg to torso.

Fibula: The fibula can also be called the calf bone. The fibula connects your knee and ankle and is located on the outside of your body alongside the tibia.



Who do people with osteoarthritis of the knee get bowlegged?

A person suffering from osteoarthritis of the knee will begin to walk differently over time.  If the arthritis is affecting the inside of a person’s knee that person is likely to start walking on the outside of their feet.  This is a gradual progression, so gradual the person may not recognize they are shifting their body weight when they walk.

This transference of body weight from the middle of their feet towards the outside of their feet causes a knee joint to bow.  Over time and thousands of steps the knee’s anatomy changes  to accommodate the change in gait.

If a person has osteoarthritis of the knee that affects the outside or lateral compartment of the knee, that person is likely to transfer their body weight towards the inside of their feet.  The resulting change in knee anatomy is the opposite of bowlegged.  This person will become pigeon toed.



Arthritis Exercises

November 20, 2011
Joint Cartilage

Joint Cartilage

 

Why does your doctor recommend exercise as a treatment option for your knee osteoarthritis?

Imagine the joint cartilage in your knee as a sponge on your kitchen sink.  When you are young the sponge is brand new and able to absorb large quantities of water.  Now think about the sponge on your sink that is well-used – it doesn’t absorb as much water as it used to, right?

Your knee is the same way.  Joint cartilage is 90% water.  The purpose of the other 10% is to retain that water to provide a cushion.  By bending your joint (exercising) what you are doing is forcing the sponge inside your knee to absorb and release water.  This keeps the cartilage hydrated and healthy.

Think about the forgotten sponge under the sink.  It is dry, brittle and sad.  It crumbles in your hands.  Exercise will help keep your knee joints lubricated and happy.



chondrocyte

chondrocyte

A chondrocyte is a cell found within cartilage.  Chondrocytes are like small factories that produce collagen and proteoglycans – the main ingredients in the cartilaginous matrix.

Collagen is a thin, ropey protein that is the primary component of connective tissue.

Proteoglycans fill in the spaces between the collagen cells.  Glucosamine and chondroitin help strengthen the cartilaginous matrix and help control knee osteoarthritis on the cellular level.



articular capsule

articular capsule

The articular capsule or capsular ligament contains the knee cap, ligaments, bursae, and menisci.  Also included is the synovial membrane and the fibrous membrane.  These membranes are separated by fatty deposits in the front and back of the knee.

Injury or wear and tear to any of these components could lead to of affect your osteoarthritis.



knee meniscus

knee meniscus

The menisci of the knee joint is a crescent-shaped cartilage structure that disperses friction in the knee joint.  The knee menisci is flat on the bottom and concave on the top.  The menisci of the knee is divided into two parts: medial (inside) and lateral (outside).  Both sides of the menisci provide structural strength to the knee when tension and torsion are applied to it.

When the meniscus is injured doctors either repair it or remove part of it.  It depends on where the tear is located, the age of the patient, and the skill of the doctor.  Either a repair or removal of the meniscus can lead to osteoarthritis.