Crepitus

One of the reasons, aside from the whole Covid situation, I reduced physical adjustments during shavasana (that wonderful final relaxation in a yoga class) is because my knees are like a creaking door from a Hammer House of Horror film. They startle students with their cracking and creaking as I squat low; not exactly the best way to relax nor the best advert for yoga.

This sound is called crepitus and is caused by the friction between roughened or irregular joint surfaces, such as in cases of osteoarthritis, or by the formation of tiny gas bubbles in the synovial fluid within the joint. (I think of it as little joint farts). Crepitus is natural and can occur in healthy joints and is often harmless, though of course it might signify injury or trauma, as with everything- it just depends.

The term "crepitus" is derived from the Latin word "crepitare," which means "to rattle" or "to crackle”, which to my ears is far too similar to the word ‘decrepit’. But it turns out they have distinct meanings. "Decrepit" comes from the Latin word "decrepitus," which means "broken down" or "worn out." So no, my farting knees do not mean I am about to kick the bucket. Phew.

Anatomy of the knee

Our knees are remarkable joints, like bridges connecting two mighty structures - the thigh bone (femur) bone and the lower leg (tibia). Unlike the skull or pelvis, there are no big bony walls in the knees, instead, they rely on ligaments, tendons, muscles, and fascia.

Ligaments are like the ropes on a suspension bridge, ensuring your knee's stability. The anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) crisscross within your knee to control its forward and backward movements. Think of them as your knee's traffic cops, ensuring everything stays in its lane. On the sides, the medial collateral ligament (MCL) and the lateral collateral ligament (LCL) provide stability, preventing side-to-side wobbling.

Tendons on the other hand, are like sturdy, yet flexible elastic bands that connect your muscles to your bones, allowing your knee to bend and straighten smoothly.

And then there's the meniscus, a C-shaped cushioning pad, which acts like a shock absorber. I’m sure you’ve heard of someone tearing their meniscus while playing sports, it's like a cushion in your couch wearing out. All these parts work in harmony, and create the knobbliness of the knee, allowing it to perform its incredible feats.

Although we say it is a hinge joint, the knee is more complex than a simple door hinge. Instead of a straight back-and-forth movement, the knee is designed with two rounded ends, (condyles), like the rounded tip of a light bulb. These condyles enable your knee to bend (flexion) and straighten (extension) and to experience internal and external rotation, as well as pivot when needed. This unique combination of movements allows you to do everything from sitting cross-legged to standing tall.

When we walk, our knees withstand compressive forces equal to three times our body weight. This can increase to four to eight times our weight while running. The knees bear 40 to 70% of this stress, depending on individual factors such as the size, shape, and thickness of our menisci. These factors can change as we age, with exercise potentially making them thicker and stronger but excessive stress potentially making the menisci thinner.

Random knee facts

The knee is the most complicated and biggest joint in human body.
Babies are born without kneecaps, which are made of cartilage and harden into bone later.
You can walk without a kneecap, but it helps to stabilize and cushion the knee joint.
Some individuals have 2 kneecaps in a knee. A bipartite patella is where the patella consists of more than one bone.
Emus, the flightless Australian birds, have knees so powerful they can kick down fences and reach speeds of up to 30 miles per hour.
The World's Oldest Knee are fossilized remains from an extinct horse discovered in Idaho, dating back over 3.5 million years.
The Guinness World Record for the most knee bends in one hour is 2,295, achieved by Silvio Sabba in Italy in 2012.
The world's first total knee replacement surgery was performed in 1968 by Dr. John Insall in New York.
In Greek mythology, the god Hephaestus created a pair of mechanical servants with bronze knees, allowing them to move gracefully like living beings.
Kangaroos have extremely powerful leg muscles and unique knee joints adapted for hopping. Their knees are so powerful that they can cover up to 44 feet in a single leap.
Ducks knees are often hidden beneath feathers, bending the wrong way compared to ours, giving the illusion of backward-bending legs.

Knee idioms

knees knocking: meaning someone is scared and their legs are shaking. It’s from the Bible, used to describe the fear of the enemies of God’s people (Isaiah 35:3).
bend the knee: meaning to submit or show respect to someone more powerful from the Latin word genuflectionem, which means "bend the knee" ("knee", genu, and "bend", flectere). The Old English word cneowian, which means "to bend the knee, kneel", is also related to the phrase. It comes from the medieval practice of kneeling before a king or lord as a sign of loyalty or homage.
weak in the knees: The phrase originated from the Bible, where it was a Hebrew expression that referred to Old Testament figures who were terrified or not steady in their faith. It can be found in ancient Hebrew and Greek versions of the Bible and in later Latin translations.
the bee’s knees: this phrase means something very good or excellent. It came into use during the 1920s when flappers compared almost anything they considered excellent to a part of an animal, such as “the cat’s pyjamas”, “the snake’s hips”, or “the elephant’s adenoids”. The phrase originally referred to something that didn't exist, and was used as a spoof item apprentices would be sent to the stores to fetch.
take a knee: this phrase means to kneel down as a gesture of respect, solidarity, or protest. Ancient civilizations in Mesopotamia, Egypt, Greece and India all adopted the gesture for different reasons from power and respect to political protest. In recent years as a form of social activism against racial injustice. It was originated by American football player Colin Kaepernick on September 1, 2016, in protest against the lack of attention given to the issues of racial inequality and police brutality in the United States
knee-high to a grasshopper: this phrase means very young or small. It comes from the comparison of a child’s height to that of a grasshopper. It originated in the United States in 1814 as the phrase "knee-high to a toad" The phrase was later modified to include other animals such as mosquito, duck, jackrabbit, bumble bee, splinter, and others. The grasshopper version of the phrase was introduced in a political opinion article describing the opposition in about 1850.
knees up: British slang for a party, especially with dancing, and dates back to the 1940s. It is connected with the popular song Knees up Mother Brown, which became a popular song in East End pubs and bars by the 1800s.

Yoga and knees

I am not sure how useful a list of ‘yoga poses for knees’ is going to be. Any yoga pose can be used to focus on the knee…

E.g. Mountain pose, standing on 2 feet. Are the knees locked? Are they knocking in? Are the quads engaged? Does that lift the knee?

E.g. Warrior II. Is there excessive strain on the bent knee? Is the knee tracking in the direction of the toes? Does the knee veer inward? How does engaging the quadriceps affect the knee joint? What about the back leg, is the knee locked? Which direction does the knee point? Where is the direction coming from the foot? The hip? The knee?

But we like our lists, so far be it for me to buck convention. So here are a few yoga poses with a focus on the knee:

Child's Pose (Balasana): This often called ‘resting’ pose places pressure and strain on the knees (which doesn’t mean it is a bad thing!). For knee issues, widen your knees and place a cushion under your hips for support, or place rolled mat or towel between thight and calves.
Bridge Pose (Setu Bandha Sarvangasana): Strengthens the quadriceps, helping to stabilize the knee joint. Modify by keeping your feet hip-width apart and or placing a block under the tail.
Standing Forward Fold (Uttanasana): Stretches the hamstrings and calves, which indirectly benefits the knees. Bend your knees slightly if you have discomfort and/or use a block on the floor to lessen the forward fold.
Tree Pose (Vrksasana): Improves balance and stability, which is also beneficial for knee health. Use a wall or hold onto a chair for support if needed. Choose your height of the bent leg: ball of foot/toe can be on the floor, the foot can be on ankle, on the calf, on the knee, on the inner thigh or heel to groin.
Extended Triangle Pose (Utthita Trikonasana): Lengthens and strengthens the inner and outer thigh muscles, supporting knee stability. Notice if you’re dumping into the knee, consider pushing into the heal and toe mound into the floor. Use a block for support if you can't reach the floor.
Low Lunge (Anjaneyasana): Stretches and strengthens the quadriceps and hip flexors. If you have knee issues, place a cushion under your back knee or lessen the depth of the lunge.
Supine Hand-to-Big-Toe Pose (Supta Padangusthasana): Stretches the hamstrings while minimizing knee strain. Use a strap or towel to reach your foot without overextending your knee.

I was undecided whether to add this pose, because it is such an advanced pose that places significant amount of strain on the knees. It certainly is not a pose for everyone.

Lotus Pose (Padmasana): Deeply stretches and opens the hips and places the knees in a position of extreme flexion. An option is to consider Half Lotus Pose instead (one foot on the opposite thigh while keeping the other foot on the floor.) or just not do lotus at all. (We need our knees more than we need lotus pose).

This list could be filled with so much more information, but what I think is more important to know is that there is a modification for every pose. Come to one of my classes and we will find a shape that suits you. If the front of the knees hurt when you kneel, how about a high blanket under the shins? If the backs of the knees hurt when you kneel, how about a rolled up towel there? If you struggle in chair pose, how about a block between the thighs? There are so many options. It’s about experimenting and playing with what works for you and your body. And always asking HOW DOES THIS FEEL IN MY BODY? Who cares that it doesn’t look like the photos. How does it FEEL? Once you start to work from within, then your yoga will take off.

And to conclude as always try to end on a light note, so I scoured the internet for some funny knee jokes, but kneedless to say they were too terrible to share.