Generality
The cartilage of the knee is the layer of cartilaginous tissue that covers the lower surface of the femur, the upper surface of the tibia and the inner surface of the patella.
The cartilage of the knee is divisible into three zones, the names of which are: medial meniscus, lateral meniscus and articular cartilage. The medial meniscus and the lateral meniscus reside exclusively on the surface of the tibia; the articular cartilage, instead, occupies the entire lower surface of the femur, the entire inner surface of the patella and the upper surface parts of the tibia not covered by the two meniscuses.
The cartilage of the knee has different functions, which are indispensable for the correct functioning of the joint and the safeguarding of its health.
Brief review of what is Cartilage or Cartilage tissue
Cartilage, or cartilaginous tissue, is a connective tissue, having a supporting function and endowed with extreme flexibility and resistance.
Composed of chondrocytes (a particular cell line) and devoid of blood vessels, the cartilage present in the human body is not all exactly the same, but has different peculiarities depending on the anatomical site and the specific tasks for which it is responsible.
Here then is that, as a result of the aforementioned peculiarities, the anatomists have thought of distinguishing the cartilage tissue in three types: hyaline cartilage, elastic cartilage and fibrous cartilage .
- Hyaline cartilage. Smooth, flexible and bluish-white in color, it is the most common type of cartilage in the human body.
Location (examples): ribs, nose, trachea, bronchi, larynx and articular surfaces.
- Elastic cartilage. Matt yellow in color, it has remarkable elasticity.
Location (examples): auricles, Eustachian tube and epiglottis.
- Fibrous cartilage. Of whitish color, it is particularly resistant to mechanical stress.
It is richly present in the joints.
See (examples): intervertebral discs, menisci of the knee and symphysis pubis.
In order to understand this article on knee cartilage, it is particularly important to keep in mind the existence and characteristics of hyaline and fibrous cartilages.
What is Knee Cartilage?
The cartilage of the knee is the indispensable cartilaginous component of the knee that covers the lower surface of the femur, the upper surface of the tibia and the inner surface of the patella .
The cartilage of the knee is fibrous, in some areas of the joint, and of the hyaline type, in others; its disposition is not accidental, but is a function of the tasks it has to perform.
For a better understanding: Anatomy and Function of the Knee
The knee is the important synovial joint of the human body, placed between the femur (superiorly), tibia (inferiorly) and patella (anteriorly).
In addition to cartilage, the knee includes several other structural elements, including:
- The synovial membrane, which covers the joint from the inside and produces synovial fluid, a fluid with a lubricating action for all the internal structures of the knee;
- The collateral ligaments, the cruciate ligaments and the patellar tendon, which, all together, guarantee the stability of the joint and the right alignment between the femur and tibia;
- The synovial bags, which are small synovial membrane pockets, filled with a lubricating liquid very similar to the synovial fluid;
Thanks to its strategic position and its particular anatomy, the knee plays a fundamental role in supporting the weight of the body and in allowing the movements of extension and flexion of the leg, during a walk, a run, a jump etc.
Anatomy
According to the most classical of anatomical descriptions, the cartilage of the knee is divisible into three zones, whose names are:
- Medial meniscus,
- Lateral meniscus and
- Articular cartilage .
The areas of the medial meniscus and the lateral meniscus localize exclusively on the tibia, while the area of the articular cartilage is divided between the inferior surface of the femur, the inner surface of the patella and the upper surface of the tibia not covered by the zones of the meniscus.
Medial meniscus: details
The medial meniscus, or internal meniscus, is the area of the cartilage of the knee in the shape of a crescent (or of C), which takes place on the medial portion of the upper surface of the tibia.
In anatomy, the term "medial" is synonymous with proximity to the sagittal plane, ie the anteroposterior axis which symmetrically separates the human body into two halves, a right half and a left half.
With reference to the medial meniscus, therefore, the medial portion of the upper surface of the tibia is nothing but the portion of this bony surface closest to the axis which divides the human body into equal and symmetrical halves.
The medial meniscus is pure fibrous cartilage, characterized by high resistance.
Lateral meniscus: details
The lateral meniscus, or external meniscus, is the area of cartilage of the knee that is more similar to an O, than to a crescent, which extends over the lateral portion of the upper surface of the tibia.
In anatomy, the term "lateral" is synonymous with distance from the sagittal plane.
With reference to the lateral meniscus, therefore, the lateral portion of the upper surface of the tibia is nothing other than the portion of this bony surface furthest from the axis which divides the human body into equal and symmetrical halves.
Like the medial meniscus, the lateral meniscus is pure fibrous cartilage, characterized by high resistance.
Articular cartilage: details
Articular cartilage is the area of cartilage of the knee that occupies almost the entire lower surface of the femur, the inner face of the patella and the areas of the upper surface of the tibia included within the two meniscuses.
Example of hyaline cartilage, articular cartilage is a white, hard, smooth, flexible cartilage layer and, thanks to the lubricating action guaranteed by the synovial fluid, also very slippery.
Did you know that ...
The area in which to take articular cartilage is part of the so-called tibial plate .
Function
In the guise of the two meniscuses, the cartilage of the knee serves to:
- Protect the knee joint from possible damage resulting from hyperextension and lower limb hyperflexion;
- Absorb any impact to the joint in the best possible way;
- Amortize the weight of the body and distribute it uniformly over the entire joint (thus avoiding that the weight of the body is concentrated in a single point);
- Help the ligaments to stabilize the joint;
- Promote a synovial fluid distribution that guarantees optimal lubrication of the articular cartilage.
Did you know that ...
Knee experts compare the medial meniscus and lateral meniscus with shock-absorbing pads.
On the other hand, in the joints of articular cartilage, the cartilage of the knee is responsible for:
- Ensure the smooth sliding of the femur on the tibia and patella. Such a slide is at the base of the joint mobility that characterizes the knee;
- Avoid direct collision between the lower surface of the femur, the inner surface of the patella and the lower surface of the tibia. If these bone portions collided, the human being would complain of pain with each movement.
Did you know that ...
Thanks to the synovial fluid, the slipperiness of the articular cartilage of the knee is 3 times higher than that of a skate on the ice and 4 to 10 times higher than that of the components which, in knee prostheses, should replace the articular cartilage layer.
diseases
The most important pathologies concerning the cartilage of the knee are lesions of the medial or lateral meniscus and arthrosis of the knee .
Lesion of the medial or lateral meniscus
Commonly known as lesions of the meniscal cartilage, the lesions of the medial or lateral meniscus are injuries to the cartilage of the knee that can occur when the joint is the victim of sudden traumas and sudden or repeated harmful stresses, which cause its progressive degeneration.
The most classic of abrupt and sudden traumatic events at the origin of a medial or lateral meniscus injury is knee sprain .
The typical cause of the degenerative lesions of the medial or lateral meniscus, on the other hand, is the continuous repetition of movements wearing the meniscal cartilage.
The lesions of the medial or lateral meniscus are responsible for a typical symptomatology, which includes: knee pain, joint swelling, reduced joint mobility, sense of knee stiffness, the emission of strange noises from the knee at the time of its movement and joint instability.
Knee arthrosis
Osteoarthritis of the knee is the chronic inflammation of the knee, resulting from the thinning of the cartilage of the knee, accomplices of degenerative type phenomena, and the consequent anomalous rubbing of the femur on the tibia.
Also known as gonarthrosis, knee osteoarthritis is, unfortunately, an irreversible and progressive condition; in fact, it produces injuries to the cartilage of the knee that are impossible to recover and are destined to worsen over time.
Usually bilateral, knee osteoarthritis causes various symptoms; in particular, it is responsible for: knee pain, redness and swelling at knee level, reduction of joint mobility, joint stiffness, crackling or crackling of the knee when bending the lower limb, joint instability and formation of osteophytes within the joint.
Osteoarthritis of the knee is a more severe condition, the more marked the degeneration of the cartilage of the knee.
