Sunny Deo - Knee Surgeon Swindon, Keyhole Knee Surgery & Sports Clinic

Knee Anatomy

Knee Anatomy and Key Terms 

Normal knee pictures
These are all pictures of the inside of a knee.
The one most people have in their minds when they think of knee problems
is the one on the right.
Knee Biomechanics
Knee Anatomy
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​There are however other structures outside the joint mechanism that can and do cause symptoms and problems. This is the first of a number of issues that arise with knee conditions and patients ability to understand exactly what’s going on.
The knee is a hinge joint between the femur (thighbone) and the tibia (shinbone). The joint is protected in front by the patella (knee cap). Articular cartilage on the ends of each bone and the underside the knee cap cushions the joint. The meniscii (cartilages) further cushion abd transfer load within and through the joint. Ligaments run along the sides and front of the knee connecting the shinbone to the thighbone at the center of the knee. These components of your knee, along with the muscles of your leg, work together to manage the stress your knee receives as you walk, run and jump.

Over time, the joint surfaces and meniscus that cushion the joint can deteriorate, causing pain and stiffness when now roughened surfaces rub directly against each other.
Knee pain originally may be only felt when a person is bending or putting pressure on the knee (such as while walking or going up and down stairs). Eventually the pain may become more frequent or nearly constant. Physical therapy, pain relieving medications or walking aids may work temporarily, but the only long-term solution in many cases may be surgery if symptoms fail to settle.  In a significant proportion of people, such deterioration within the joint may cause no symptoms or problems at all.

There are two principal groups of muscles involved in the knee, the quadriceps muscles (located on the front of the thighs), which straighten the legs, and the hamstring muscles (located on the back of the thighs), which bend the leg at the knee.
Tendons are tough cords of tissue that connect muscles to bones. Ligaments are tough cords of tissue that connect bone to bone. Some ligaments on the knee provide stability and protection of the joints, some ligaments limit forward and backward movement of the tibia (shinbone).
This is what these structures look like when we visualise them directly during an arthroscopy (keyhole procedure to view the interior of the knee joint)

Key terms
​​Femur - A bone of the leg situated between the pelvis and knee in humans. It is the largest and strongest bone in the body.
Bursa - A sac or saclike bodily cavity, especially one containing a viscous lubricating fluid and located between a tendon and a bone or at points of friction between moving structures.
Synovial membrane - The connective-tissue membrane that lines the cavity of a synovial joint and produces the synovial fluid. Also called synovium. This will thicken following acute injuries and chronic conditions (synovitis) 
Articular cartilage - The joint surfaces covering the inside surfaces of the bones forming a synovial joint. Also called arthrodial cartilage, diarthrodial or investing cartilage. 

Capsule - a tough, flexible connective tissue layer that site around the whole knee joint.
Tibia - The inner and larger of the two bones of the lower human leg, extending from the knee to the ankle.
Patella - A flat triangular bone located at the front of the knee joint. Also called kneecap.
Synovial fluid - A clear, viscid lubricating fluid secreted by membranes in joint cavities, sheaths of tendons, and bursae.
Synovium - The inner lining of all mobile, synovial joints. This is a specialised tissue which will inflame in the presence of acute or chronic injury

Meniscus - A cartilage disk that acts as a cushion between the ends of bones that meet in a joint.
Patellar tendon - The part of the tendon of the extensor mechanism that extends from the patella to the tibia, sometimes called the patellar ligament.
Quadriceps tendon -  The tendon attaching the bulk of muscles at the front of the thigh to the top of the kneecap.
Anterior Cruciate Ligament (ACL) - one of two deep central ligaments within the knee which is frequently invloved in significant twiting knee injuries.
Medial Collateral Ligament (MCL) - The most frequently injured ligament lies on the inner side of the knee.
Posterior Cruciate Ligament (PCL) - The other, slightly larger and less commonly injured central knee ligament.
Lateral Collateral Ligament (LCL) - The main ligament complex on the outer side of the knee.
Postero-Lateral Corner (PLC) Ligament -  an additional complex of 3 ligaments at the back/other side of the knee.
Postero-Medial Corner (PMC) Ligament - a capsular condensation on the back, inner side of the knee.