Understanding The Knee Joints


The knee joint, one of the largest and most complicated joints in the human body, is essential for mobility. It is the crucial link between the thigh bone (femur) and the shin bone (tibia), functioning similarly to a hinge on a door. This design allows your leg to bend, allowing you to perform everyday tasks including walking, standing, running, and sitting.

The knee joint is constructed of bone, ligaments, tendons, and cartilage, and it is supported by massive muscle groups that cross it.

The knee’s ability to support forces larger than your body weight demonstrates its power. However, this capability exposes the knee to potential injury. Its role in absorbing enormous mechanical stress makes it one of the most injury-prone joints.

Understanding the form and function of the knee can help you recognise potential problems and make proactive efforts to keep your knee healthy. Whether it’s through preventive maintenance, regular exercise, or recognising the early signs of knee strain, caring for your knee joint is critical for maintaining an active and healthy lifestyle.

The fundamental structure of the knee joint (knee anatomy)

The knee joint is a critical component of the musculoskeletal system, allowing for movement and supporting the body’s weight. Anatomically, it is essentially made up of three bones: the femur (thigh bone), the tibia (shin bone), and the patella (kneecap). The femur’s rounded ends, known as condyles, rest against the tibia’s flat surface, while the patella sits in front of the joint, providing protection and leverage. This configuration enables the knee to operate efficiently as a hinge, allowing for necessary actions such as bending, straightening, and small rotation.

Supportive Structures Enhancing Stability

Ligaments, tendons, and cartilaginous tissues all work together to keep the knee stable. The knee’s stability is dependent on four key ligaments: the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL), all of which prevent excessive movement that could result in injury. The menisci are two crescent-shaped cartilage pads that sit between the femur and tibia. They cushion the joint, absorb shock, and improve stability. Tendons, notably the big quadriceps tendon that connects the quadriceps muscle group to the patella, and the patellar tendon, which connects the patella to the tibia, are essential for movement and stability.

Synovium and Joint Fluid: Enhanced Mobility and Protection

The knee joint’s motion is supported by the l membrane, which secretes synovial fluid. This fluid lubricates the joint, minimising friction and wear on the articulating surfaces. The synovial fluid also nourishes the cartilage, so preserving its health and function. Furthermore, the joint capsule encloses the knee, keeping the joint structures and fluid in place and allowing the knee to function smoothly and efficiently.

Muscles Controlling Knee Motion

The dynamic movement of the knee is primarily regulated by strong muscle groups that surround and support the joint. The quadriceps muscles, positioned in the front of the thigh, are among the most important for knee mobility. They are made up of four muscles: the vastus lateralis, vastus medialis, vastus intermedius, and rectus femoris. These muscles work together to extend the leg at the knee and are essential for straightening the leg from a bent position. On the posterior (back) side, the hamstring muscles, which include the biceps femoris, semitendinosus, and semimembranosus, aid in knee flexion (bending of the knee) and thigh extension at the hip. Furthermore, the calf muscles, which include the gastrocnemius and soleus, link to the knee via tendons and aid in bending and stabilising it while walking, running, and jumping. These muscles are required not just for movement but also for stabilising the knee during dynamic activities, making a significant contribution to the knee joint’s overall functionality and durability.

Why does my knee swell after an injury?

Swelling is frequent after a knee injury. Depending on the intensity and nature of the injury, this swelling may be mostly composed of synovial fluid or blood. In cases of severe trauma, such as a fracture or ligament rupture (e.g., ACL), a blood artery may be injured, resulting in bleeding into the joint area. In contrast, less severe injuries, such as a meniscus tear or arthritis, cause the body to produce more synovial fluid. This increased fluid helps to lubricate the joint and separate the injured surfaces, minimising friction and discomfort.

However, if the underlying cause of the swelling is not addressed, the body will continue to create fluid, resulting in persistent swelling. Rapid swelling can raise pressure within the knee capsule, causing significant pain. If the knee swells frequently, the excess fluid may eventually drain into the back of the knee, causing a Baker’s cyst. This cyst is a fluid-filled sac that temporarily stores extra synovial fluid, but it can also cause pain in the knee.

Understanding why knee swelling occurs and addressing the underlying cause as soon as possible can help control symptoms and prevent long-term consequences. If you have chronic knee swelling, you can try a knee compression sleeve to help manage your symptoms, but it is unlikely to treat the underlying cause.

The normal human anatomy of a knee

Common Knee Problems.

Osteoarthritis is a degenerative illness that causes the cartilage in the knee joint to wear away over time.

Meniscal Tear Knee: 

Injury to the shock-absorbing cartilage (meniscus) between the bones of the knee, which frequently occurs during sports. Knee meniscus injury is one of the most prevalent cases presented to an orthopaedic surgeon.

Ligament Injuries:

ACL (Anterior Cruciate Ligament) injury is common in sports and causes severe stretching or rupture of the ACL in the knee.

PCL (Posterior Cruciate Ligament) Injury: Often caused by a direct impact to the front of the knee.

MCL (Medial Collateral Ligament): Injury is caused by a force pushing the knee sideways.

LCL (Lateral Collateral Ligament) Injury: Injury to the ligament on the outside of the knee, which is less prevalent than MCL injuries.

Patellar Tendinitis (Jumper’s Knee): Inflammation of the tendon that links the patella to the shinbone; commonly found in athletes who jump frequently.

Patellofemoral Pain Syndrome (Runner’s Knee): is a condition that causes pain at the front of the knee and around the patella. It is frequent among runners and cyclists.

Dislocated Kneecap: This occurs when the patella moves out of its normal place in the knee joint.


Patellar fractures are breaks in the kneecap caused by falls or direct impact.

Distal Femur Fracture: A break at the top of the shinbone or the bottom of the thighbone near the knee.

Iliotibial Band Syndrome (ITBS) is an overuse injury that causes pain on the outside side of the knee, particularly among distance runners.

Diagnostic Tools for Knee Problems.

Physical Exam:

Visual Inspection: The doctor examines the knee for symptoms of swelling, redness, or deformity.

Palpation involves feeling the knee to detect soreness or abnormal swelling.

Range of Motion Tests: These involve bending and straightening the knee to determine the joint’s mobility and the existence of pain while moving.

Special Tests: Various manoeuvres (e.g., McMurray’s test, Lachman test) are used to assess the integrity of knee structures such as ligaments and meniscus.

Imaging tests:

X-rays: These provide images of the bones and can assist detect fractures, misalignments, or degenerative changes in the knee joint.

MRI (Magnetic Resonance Imaging): This technique employs powerful magnets and radio waves to provide detailed images of both hard and soft tissues in the knee. This is especially beneficial for detecting soft tissue injuries such as ligament tears, meniscus tears, and cartilage damage.

CT Scan (Computed Tomography): This instrument combines X-rays shot at various angles to provide cross-sectional images of the knee. It’s particularly beneficial when assessing complicated fractures.

Ultrasound is an imaging technology that employs sound waves to create images of soft tissues. It is useful for examining tendons and ligaments around the knee and directing operations such as injections.

Laboratory Tests:

Synovial Fluid Analysis: Fluid is sometimes collected from the knee (aspiration) to look for evidence of infection, or disease (such as gout or rheumatoid arthritis), or to determine the origin of fluid buildup.

Treatment Options For Knee Problems

Knee difficulties can be effectively managed with several treatment options customised to the severity and nature of the injury or ailment. Non-surgical treatments are frequently the first step, and may include physical therapy to strengthen muscles around the knee and improve flexibility; medications such as anti-inflammatories and analgesics to reduce knee pain and swelling; and corticosteroid injections to provide temporary relief from arthritis symptoms. A knee brace or knee support can help stabilise the area and prevent further injury, while a hinge knee brace provides more mobility control.

When non-surgical procedures are insufficient, surgical options may be considered. Arthroscopic surgery, a minimally invasive approach, is commonly used to repair or remove damaged cartilage, rebuild torn ligaments, and remove loose bodies from the knee joint. In more serious cases, partial or total knee replacement may be required to replace damaged elements of the knee with artificial components, restoring function and relieving discomfort. A knee cushion can be used after surgery to preserve appropriate alignment and alleviate pressure on the knee during recuperation.

Preventive Care and Maintenance of Knee Health

1. Regular exercise:

Strength Training: Strengthening the muscles surrounding the knee joint, particularly the quadriceps and hamstrings, helps to stabilise and protect the knee.

Flexibility & Stretching: Regular stretching can assist in maintaining range of motion and flexibility, lowering the risk of injury.

Low-Impact Aerobics: Activities like swimming, cycling, and walking can keep joints in good working order without causing additional stress.

2. Weight Management: 

Every time you take a step 3 times your body weight goes through your knee joint. So even carrying a small amount of extra weight can greatly enhance these forces. Maintaining a healthy weight is vital since excess body weight increases the stress on knee joints, particularly during daily activities like walking or climbing stairs. Losing weight can greatly reduce the chance of developing osteoarthritis and improve existing knee discomfort.

3. Injury-Prevention Techniques:

To avoid putting too much strain on your knees, use proper techniques and form when participating in sports or exercising. The use of suitable sports gear and personal protection equipment can also help to reduce danger.

4. Understanding Body Signals:

It is critical to be aware of indicators of discomfort and pain that may signal overuse or potential injury. Early attention can prevent more serious injuries and longer recovery times.

Individuals who implement these preventative care measures can not only lower the likelihood of knee injuries but also improve their overall knee function and health. Regular management of knee health promotes longevity in mobility and quality of life.

How to Strap / Tape a Knee.

Strapping or taping your knee is an effective way to provide support and stability to the joint when recovering from an accident or preventing injuries during activities. To correctly tape a knee, make sure the skin is clean and dry so that the tape adheres better. For sensitive skin, consider applying a pre-tape spray or under wrap. Begin with a base of flexible tape beneath the kneecap to provide support, followed by a more stiff knee strap or tape above and below the kneecap in a crisscross pattern to stabilise the tendons and ligaments. To avoid circulation difficulties, apply knee tape snugly but not too tightly. Consider viewing a video or talking with a physiotherapist to learn the proper technique for maximising the benefits of tape and avoiding future injury. This procedure is especially good for athletes or others who lead active lifestyles and need extra knee support during physical exercises.

Why does my knee click?

If you hear a clicking sound in your knee, it is usually caused by the movement of the kneecap or the stretching of ligaments in the joint. While this is a normal occurrence without underlying knee pain, repeated clicking accompanied by discomfort may indicate misalignment or cartilage damage. A knee brace or knee strap can give crucial knee support by aligning the knee cap and stabilising the joint, potentially reducing the clicking. It is critical to monitor the noises and sensations in your knee, especially if the clicking is accompanied by discomfort or swelling. In such instances, wearing a knee support can not only relieve knee discomfort but also protect against additional harm.

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As a leading Perth orthopaedic surgeon, Rhys performs a range of knee surgeries – from knee replacements and partial knee replacements to knee arthroscopies.