Maximus Gage
The knee is the body's largest joint, allowing humans to walk, run, jump, and sit. It is a hinge joint that sits between the thigh and the shin, connecting the lower and upper leg. The knee is made up of bones, cartilage, muscles, ligaments, and nerves. The knee's main functions are made possible by the quadriceps and hamstrings. The quadriceps is a group of four muscles that sit on the front of the thigh, allowing the knee to straighten. The hamstrings are a group of three muscles that sit at the back of the thigh, allowing the knee to bend.
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What You'll Learn
Popliteus muscle
The popliteus muscle is a small, flat, triangular-shaped muscle in the lower leg. It is a deep muscle, forming the floor of the popliteal fossa, and is one of the main posterolateral stabilisers of the knee joint.
The popliteus muscle assists in knee flexion and its function is decided according to the position of the lower extremity, i.e. weight-bearing or non-weight-bearing. In a non-weight-bearing position, it is a primary internal rotator of the tibia. During weight-bearing, 'locking' of the knee occurs, where the femur medially rotates on the tibia, allowing for full extension without muscular expenditure.
To 'unlock' the knee, the popliteus muscle needs to contract, causing flexion and lateral rotation of the femur on the tibia. This gives the muscle the term 'key' to the locked knee. The popliteus is also involved in both the closed chain phase and open-chain phase of the gait cycle. During the closed chain phase, when the foot is in contact with the ground, the muscle externally rotates the femur on the tibia. In the open-chain phase, or when the limb is not in contact with the ground, the popliteus muscle medially rotates the tibia on the femur.
The popliteus muscle is supplied by the tibial nerve, from spinal nerve roots L4 or L5 through S1, with approximately 2 to 3 parallel tibial nerve branches. The entry point of the nerve is the lateral distal margin of the muscle, which is found inferior to the fibular head. After entering the muscle, the nerve splits into anterior, medial, and lateral distributions.
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Knee injuries
The knee is the body's largest joint and is also one of the most frequently injured. The knee joint is made up of bones, cartilage, muscles, ligaments, and nerves. The popliteus muscle is a small, thin, flat, triangular-shaped muscle in the lower leg that forms the floor of the popliteal fossa, a shallow pit at the back of the knee. It is one of the main stabilisers of the knee joint, causing medial and lateral rotation, and assists in knee flexion.
There are many different types of knee injuries. One common injury is a strain or tear of the hamstring muscle, which can lead to pain behind the knee and difficulty bending it. This can be caused by overstretching or sudden, forceful movements. Another common injury is a pulled tendon, which can cause sharp pain at the back of the knee and thigh, and may make walking difficult. Tendinitis, or inflammation of the tendon, is often caused by overuse and is common in runners. In some cases, a knee injury can lead to a collection of fluid within the knee, known as a popliteal cyst or Baker's cyst, which can be felt at the back of the knee.
Diagnosing a knee injury typically involves a physical examination and a discussion with a doctor about how the injury occurred. X-rays and MRI or ultrasound scans can be used to assess the damage. Milder injuries often heal naturally with rest, ice, and anti-inflammatory medication, while more serious tears may require surgery. Braces, crutches, physiotherapy, and exercise plans can also be used to protect and strengthen the knee during the healing process.
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Knee pain
There are many possible causes of knee pain, ranging from a simple muscle strain or tendonitis to arthritis. Knee pain can also be caused by sports injuries, but you don't have to be an athlete to experience this type of pain. Some common knee injuries include sprains, strains, and tears. Tendonitis, or swelling of the tendon, can also cause knee pain. This condition can affect both children and young people. Osgood-Schlatter's disease is another common knee problem, especially in children and young adults. The bony lump below the kneecap becomes painful and swollen during and after exercise.
If you are experiencing knee pain, it is important to visit a healthcare provider. They will be able to diagnose the cause of your pain and suggest appropriate treatments. In the case of long-term knee pain, doctors will try to break the inflammatory cycle by controlling the substances that cause inflammation and preventing further injury to the tissues in the knee. This can be done through protection, rest, ice, compression, and elevation (PRICE therapy). For short-term pain that is not disabling, PRICE therapy and over-the-counter anti-inflammatory medications are recommended for a week. If symptoms persist, it is advised to see a doctor, physical therapist, or sports medicine orthopedic specialist.
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Knee anatomy
The knee is the largest joint in the body. It is a synovial joint, which means it has the most freedom to move. The knee moves like a hinge, allowing you to sit, squat, walk, or jump. The knee is also one of the most commonly injured joints.
The knee joint connects the thigh bone (femur) to the shin bone (tibia). The patella, or kneecap, sits over the other bones at the front of the knee. The ends of these bones are covered in hyaline cartilage, a slick, elastic material that absorbs shock and allows the bones to glide smoothly against one another as they move. The surfaces of the femur, tibia, and patella that touch have a hyaline cartilage lining.
The knee contains two articulations: patellofemoral, where the patella meets the femur, and tibiofemoral, where the tibia meets the femur. The bones are held together by a joint capsule, which consists of two distinct layers: an outer layer of dense connective tissue and an inner membrane, called the synovium, which secretes a fluid to lubricate the joint.
The knee contains several ligaments, including the lateral collateral ligament (LCL), which stabilizes the outer part of the knee, and the medial collateral ligament (MCL), which gives stability to the inner part of the knee. The knee also contains the anterior cruciate ligament (ACL), which is located in the center of the knee and prevents excessive forward movement of the tibia, and the posterior cruciate ligament (PCL), which is behind the ACL and prevents excessive backward shifting of the tibia.
The popliteus muscle is a small, thin, flat, triangular-shaped muscle in the lower leg. It is a deep muscle of the knee joint, forming the floor of the popliteus fossa. It is one of the main posterolateral stabilizers of the knee joint, causing both medial and lateral rotation of the knee. The popliteus tendon passes beneath the LCL and the tendon of the biceps femoris. The popliteus muscle assists in knee flexion and is involved in both the closed chain phase and open-chain phase of the gait cycle.
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Knee function
The knee is the body's largest joint, connecting the thigh bone (femur) to the shin bone (tibia). It is also one of the most complex joints in the body and is constructed by four bones and an extensive network of ligaments and muscles. The knee is a synovial joint, which means it has the most freedom to move. It is also a hinge joint, meaning it opens and closes in one direction, like the hinges that hold a door in place.
The knee joint is made up of three compartments: the medial compartment, the lateral compartment, and the patellofemoral compartment. The medial compartment is the joint between the femur and tibia on the inner side of the knee. The lateral compartment is the joint between the femur and tibia on the outer side of the knee. The patellofemoral compartment is the joint between the kneecap and its groove on the femur.
The knee's main movement is flexion-extension. During flexion and extension, the tibia and patella act as one structure in relation to the femur. The patella, or kneecap, is a triangular sesamoid bone that increases the efficiency of quadriceps contractions. Contraction of the quadriceps pulls the patella upwards and extends the knee. The quadriceps muscle group is made up of four different individual muscles that join together to form a single tendon that inserts into the anterior tibial tuberosity.
The knee joint also contains cartilage, which acts as a shock absorber and provides a well-lubricated surface that allows for smooth, low-friction movement between the bones. The synovial membrane produces synovial fluid, which lubricates the knee joint and provides nourishment to the surrounding structures. The knee also contains ligaments, which are bands of tissue that connect the thigh bone to the lower leg bones. The two collateral ligaments are like straps on opposite sides of the knee, with the medial collateral ligament (MCL) on the inner side and the lateral collateral ligament (LCL) on the outer side. The cruciate ligaments are inside the knee joint and control the way the knee moves front to back.
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Frequently asked questions
The popliteus muscle is a small but important muscle located in the posterior aspect of the knee joint. It is often referred to as the "key of the knee" or the "key to the locked knee" as it is responsible for unlocking the knee joint.
The primary function of the popliteus muscle is to unlock the knee joint by laterally rotating the femur on the tibia when the foot is in contact with the ground. It also helps to stabilise the knee joint during weight-bearing activities and controls the internal and external rotation of the tibia during walking and running.
Pain behind the knee can be caused by various factors, including hamstring injuries, a Baker's cyst, meniscus tears, tendon injuries, and osteoarthritis, among others.
It is recommended to visit a healthcare professional if you experience pain or other symptoms in your knees. They will be able to diagnose the issue and suggest appropriate treatments to help you return to your normal activities.
