Knee

Synonyms in further meaning

German Knie

Explanation

Here you can observe the most important anatomical fundamentals of a healthy knee joint and gain an overview about all essential maladies of the knee joint with a short definition of each affliction. In order to obtain detailed information, please follow the link to the appropriate explanation.

STRUCTURE OF THE KNEE JOINT

Anatomy

The Anatomy of the Healthy Knee Joint:

The knee joint is the largest joint of the human body and it establishes the mobile linkage between the thighbone (Femur) and the shinbone (Tibia). Three bones comprise a framework of the knee joint together with a complex capsular and ligament apparatus (lateral and cruciate ligaments).

These are:

• The thighbone roll (Femur condyle)
• The shinbone head (Tibia plateau)
• The knee cap (Patella).

Anatomy of the knee joint: Thigh muscle (Musculus rectus femoris) Thighbone (Femur) Quadriceps tendon Knee cap (Patella) Knee cap tendon (Patellar tendon) Knee cap tendon insertion (Tuberositas tibiae) Shinbone (Tibia) Splintbone (Fibula)

In the figure it can be seen that the bones have close contact to one another. In order that a pain-free and unhindered mobility of the knee joint can occur, the bones have been coated with a very smooth, white cartilage layer on their respective contact surfaces, the so-called hyaline cartilage. Only in such a manner is a pain-free and unhindered mobility of the knee joint possible. The hyaline cartilage is composed of cartilage cells and matrix tissue. While cartilage cells of adults have lost their capability to divide and thus to be healed, the cartilage cells of children can repair cartilage damage by propagation. The cartilage cells are embedded in matrix tissues which they have produced themselves. These consist of water to a great extent and supporting connective tissue; they confer stability and elasticity to the cartilage tissue.

In the knee joint, itself, one differentiates the joint coupling between the thighbone condyles and the knee cap (Femoropatellar joint) as well as between the thighbone condyles and the shinbone head. The connection between the thighbone condyle and the knee cap is the portion of the knee joint that is stressed the most. When one is climbing stairs, for example, this joint is stressed by more than three-fold of the body weight.

The most important tendon of the knee joint is the knee cap tendon (patella tendon / patellar tendon), which stretches as a strong band from the knee cap on the anterior side of the knee joint to the shinbone (Tuberisitas tibiae).

The knee joint is enclosed by the knee capsule, whose inner portion is designated as the inner skin of the joint (synovia). It produces synovial fluid that is important for nourishment of the cartilage. In adults, the cartilage tissue is nourished mainly by diffusion (passive transport) from the synovial fluid, because it is not perfused with blood, in contrast to other tissue types of the body (muscles, bone, skin etc.). Therefore, the usual nourishment via blood circulation does not function. Movement of the knee joint mixes the synovial fluid and improves the uptake of nutrients by the cartilage cells (chondrocytes). Furthermore, the proper amount and composition of the synovial fluid is decidedly significant for lubricating the knee joint. Through this means, the friction of corresponding cartilage surfaces is minimized upon movement. Hyaline cartilage possesses an extremely low frictional resistance that is lower than all known artificial material couplings.

Between the thighbone condyle and the shinbone, two fibrous-cartilaginous discs (meniscus) are located, which lie as buffers between the cartilage surfaces, and which are important for evenly distributing pressure in the knee joint upon stress. The cruciate ligaments traverse the knee joint and connect the thighbone with the shinbone. The principle task of the cruciate ligaments is to guarantee a stable knee joint and thereby to enable a harmonious movement process that is as friction-free as possible. Upon stress, both cruciate ligaments prevent the knee from moving forward (anterior cruciate ligament) or backward (posterior cruciate ligament). In their stabilizing action, they are supported by lateral ligaments (collateral ligaments), the knee joint capsule and muscles that surround the knee.

The musculature that surrounds the knee determines the function of the knee joint. Movement is only made possible through them. Furthermore, they support the passive joint stabilization of the capsule / ligament apparatus. The extension musculature of the knee joint (quadriceps musculature) on the anterior side of the thighbone is very strongly developed. Upon bending the knee joint, the muscles are activated instinctively, in order to prevent a buckling of the knee when walking. The most important flexors of the knee joint are the ischiocrural musculature on the posterior side of the thighbone, which are also active in stabilizing the knee joint. The ischiocrural musculature especially supports the anterior cruciate ligament; therefore, its training is especially important following a ruptured anterior cruciate ligament.

Thighbone (Femur) Inner meniscus Anterior cruciate ligament (ACL) Shinbone (Tibia) Outer meniscus