The Anatomy of the Knee

There are over 300 joints in the human body. The largest of these joints is the knee. I am fascinated by the knee because of it’s complexity and vulnerability. I have also suffered from knee pain for the majority of my life, so I’d like to take a closer look at it’s function.
The knee is made up of four main substances: bones, cartilage, ligaments and tendons. The anatomy of the knee consists of the Femur (thighbone), the Tibia (shinbone) and the Patella (kneecap). These bones are held together by four different ligaments: the Anterior Cruciate Ligament (ACL), the Posterior Cruciate Ligament (PCL), the Medial Collateral Ligament (MCL) and the Lateral Collateral Ligament (LCL).
Within this joint there is a layer of cartilage sitting on the flat area of the Tibia, the Meniscus. The Meniscus acts as a stabilizing cushion, or shock absorber, for the knee. Finally, the muscles that cause the knee to move are connected to the bones by tendons. The Quadriceps tendon connects the front thigh muscle to the patella. The Patellar tendon connects the patella to your shinbone.
There are also many muscles around the knee joint that support it’s function. The main muscles that aide the knee are the quadriceps, hamstrings, iliotibial band (IT band) and the gastrocnemius (calf).
The knee is one that is most easily injured according to the American Academy of Orthopedic surgeons. Injuries to the knee can include fractures, dislocations, sprains and ligament tears. Signs of injury typically include pain and swelling. Other signs might include a popping noise, sharp pain or immobility. It is also common for the knee to feel as though it is “locked” and possibly give way allowing you to lose your step. I find this happens to me often. This is more common in those that experience hyper mobility.
The most common bone broken around the knee is the patella. Or, a simple dislocation can occur when the bones are out of place. All of the bones surrounding the knee can be forced out of alignment or just slip out of place. Many fractures and dislocations are caused by high energy trauma, such as falling from significant heights, vehicle accidents or high contact sports.
The most commonly discussed knee injury is of the ACL. This injury is also most likely caused during sport specific activity. Athletes who participate in high contact sports such as football, soccer, basketball, volleyball and softball are more likely to tear their ACL. A tear, whether minor or major, can be caused from changing direction quickly or landing incorrectly from a powerful jump. Typically when one tears their ACL, damage to other structures in the knee occur.
A less common injury is a tear to the PCL. This is a common injury to those who hyper extend or have had a blow to the front of the knee. Once injured, any pressure to the front of the knee can cause discomfort or even pain.
Injuries to the MCL and LCL are usually caused by force or pressure to the sides of the knees. Injuries to the MCL are usually caused by force to the outside of the knee and are often sport related. Force to the inside of the knee that push the knee outward typically injure the LCL. LCL injuries occur less frequently than other knee injuries.
As these ligaments stretch and tear over time, it is difficult to get them back to their regular state. Think of a slinky, that toy you used to play with as a kid. The more you pull on the slinky, the harder it is to get the springs to be wound tight. Although, ligament injuries can heal themselves over time with rehab and yoga, it is pertinent that we take good care of the knee to prevent these ligaments from over use.
Another very common knee injury is that of the meniscus. Sudden meniscal tears occur more often than not during sport performance. Meniscal tears may also occur as a result of arthritis or aging. Even an unsettling twist in the shower can cause a tear if the meniscus is already weakened from age or over use.
Tears can also occur in the quadriceps and patellar tendons. These injuries affect all shapes and sizes but typically occur in middle aged athletes. Falling, blunt force trauma or an improper jump landing can cause tendon injury.
As soon as you experience sign of injury, seek immediate attention from a licensed doctor. Many injuries can be treated with non invasive remedies such as RICE. As a kid, I was taught the RICE method. 25 years later, I’m still using this method and swear by it. I’m also happy to hear that the AAOS is still promoting this method for rehabilitation. This method is great for the knee but can be used for any injury. RICE simply stands for Rest, Ice, Compress and Elevate. This allows the blood flow to drain away from the injured area, alleviates pain, reduces inflammation and helps speed up the recovery process.
If you think you have fractured a bone, you need to immobilize the joint. You may need a brace or cast to hold the bones in place to heal properly. To further protect the knee, be sure to take weight off the area by using crutches or another alternative.
Physical therapy and some yoga postures can also help to rehabilitate injuries properly. Specific asana can restore function to the knee and strengthen the leg muscles supporting it. Many fractures and ligament injuries can require surgical treatment. In order to avoid this route, it is imperative to find a steady, safe yoga practice as a means of prevention.
The thing about anatomy is that it is not simple. Our bodies are so intricate and fascinating. Just take a look around you. Every body is different. We are all born with similar, but very different skeletal systems. It must be noted that not every body is the same. Therefore, not every body will move in the same way, suffer the same injury or rehabilitate similarly. Everyone’s knees affect their hips, back, and ankles in different ways. Age, weight, height, genetics and activity all affect our make up. Just something to think about when teaching or practicing any form of movement.
There are a few poses that society argues are bad for the knee including Lotus Pose (Padmasana), Heros Pose (Virasana) or even Pigeon Pose (Eka Pada Rajakapotasana). However, I’d like to argue that these poses can be very restorative for the knee when practiced properly. It is very important to warm up the body before practicing asana in general. Listen to your body and be patient. Bending and moving the knee properly can break up, or re-align scar tissue that has produced and tightened over time. Breaking up scar tissue will alleviate pain in the long run and allow for more mobility.
According to the Yoga Journal there are 7 ways to protect your knees during yoga practice.
1. Avoid Hyperextension. This can be difficult to do if you naturally hyper extend. Typically women suffer from this hyper mobility issue. It is important to not lock out the knee by keeping a slight bend at the joint and engage the quadricep muscle to support the knee. Hyperextension is common in poses where the legs need to be straight and strong such as Triangle Pose (Trikonasana) and Seated Forward Bend (Paschimottanasana). In seated forward bends you can roll up a small blanket and place it under the knees to avoid hyperextension.
2. Strong, grounded feet in Mountain Pose (Tadansana). Proper alignment in your feet is key. Grounding down through all four corners and lifting through the inner arches of the feet builds strength evenly in the knees. Having strong feet in every pose allows the kneecap to glide with ease and avoid wearing down the cartilage.
3. Knee alignment is important. Take Warrior II (Virabhadrasana II) and Side Angle Pose (Parsvokonasana) for example. The knee should be directly over the ankle forming a 90 degree bend in the leg. The knee cap should face forward and align with the second toe in most cases. Press evenly through the back foot and engage the back quadricep.
4. Listen to your body. Signs may be subtle but important. If you feel aching or sharp pain, come out of the pose. You are looking for a pleasurable discomfort to build strength and grow. You are not looking for pain. Contrary to popular belief, pain is not weakness leaving the body. Pain is pain. Pain is injury.
5. Build strength in balancing postures such as Eagle Pose (Garudasana). This is a great pose for breaking up scar tissue without causing stress on the knee with a deep twist.
6. Don’t discount the use of props. They are there for a reason. Props can be a great tool to use in seated postures to support the knee. You never want the knee just hanging in space. A hanging, tired knee could cause some ligaments to over stretch and work too hard. For example, sit on a block in Hero Pose (Virasana) or prop a block under your knee in half Pigeon.
7. The last and most important tip is to warm up the body for hip openers. Hip stretches could include Bound Angle Pose (Baddha Konasana) or Cow Face Pose (Gomukhasana). Always practice these hip openers when warm and ready. They can be great stretches for knee repair and increased performance.
The knee is a fabulous tool for movement. Without it, we could not walk, run, sit, jump or practice yoga. Take care of your knees and they will take care of you.
SOURCES: Department of Research & Scientific Affairs, American Academy of Orthopaedic Surgeons. Rosemont, IL: AAOS; February 2014. Based on data from the National Ambulatory Medical Care Survey, 2010; Centers for Disease Control and Prevention; Yoga Journal.

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2 Responses
  1. Darlene

    Thank you for sharing such valuable information. As a physical education teacher, coach and former collegiate and international athlete, I value the yoga practice for prevention of injuries. I feel many of our young athletes are overworking their bodies without proper recovery and healthy practices to sustain themselves to remain active past collegiate play.

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