Cartilage

Cartilage: what it is and what it is used for

Articular cartilage is an elastic tissue with remarkable resistance to pressure and traction (it is a specialized connective with a supporting function). It has a pearly white color and covers the ends of the joint bones, protecting them from friction. Its function is similar to that of a shock absorber bearing which with its action safeguards normal joint relationships and allows movement.

These important characteristics are permitted by its particular chemical constitution. In fact, inside the cartilage there are cells, called chondrocytes, which - especially when they are young (chondroblasts) - have the task of producing the fundamental substance. This substance consists mainly of water, collagen fibers, proteoglycans, hyaluronic acid and glycoproteins. Beyond the names, what is important to remember is that cartilage is composed of a fluid part (which gives it the ability to absorb traumas) and a solid part (which increases its resistance). These phases interact with each other to ensure a kinematic motion without friction and to protect the articular surfaces from wear.

Cartilage tissue is not vascularized as it has no blood capillaries. Cartilage (excluding the articular hyaline cartilage) is surrounded by a layer of dense connective tissue (perichondrium), rich in blood vessels, which allow it to feed by diffusion. Feeding chondrocytes by diffusion is a slow and much less effective process than blood circulation; for this reason the regenerative capacities of this fabric are very low.

In our body we commonly distinguish three types of cartilage tissue with different characteristics and functions:

• hyaline cartilage: bluish-white in color is the most abundant cartilage type . In the fetus it constitutes a large part of the skeleton and as it grows it is almost completely replaced by bone tissue *. In the adult it constitutes the costal, nasal, tracheal, bronchial and laryngeal cartilages and covers the articular surfaces. The cartilage is covered with a thin envelope of compact connective tissue called perichondrium. This tissue disappears near the articular surfaces.
• elastic cartilage : opaque yellow in color, it has particular characteristics of elasticity . It constitutes the scaffolding of the auricle, of the epiglottis, of the Eustachian tube and of some laryngeal cartilages.
• fibrous cartilage: whitish in color it is particularly resistant to mechanical stress. It is found at the insertion point of some tendons on the skeleton, in the intervertebral discs, in the menisci of some joints (knee) and in the pubic symphysis

* until the end of the growth between epiphyses and diaphyses of long bones there remains a small area called the epiphyseal disk which continues to proliferate cartilage tissue. This tissue is gradually transformed into bone ensuring normal skeletal elongation. By reaching maturity the disc is also ossified and the bone can no longer grow.

Cartilaginous lesions

The strength and functionality of cartilage tissue are exceptional. Suffice it to say that it normally withstands almost 80 years of continuous stress and that no man-made device can boast the same properties.

However, during the life span this resistance can be undermined by a series of factors that expose the cartilage to more or less important injuries. Normally cartilage lesions are classified into two distinct categories:

primary or post-traumatic that arise as a result of mechanical incidents (fractures, sprains, stress fractures) or are linked to genetic factors

secondary or degenerative that arise as a result of continuous stress or problems of metabolic or immune nature (for example following a deficiency of the immune system such as for rheumatoid arthritis)

Regardless of its nature, a lesion of articular cartilage marks the onset of osteoarthritis.

Osteoarthritis is, by definition, a degenerative pathology of articular cartilage. In Italy, over 4 million people, especially the elderly, suffer. More than 80% of people over 55 have radiographic signs of arthrosis (especially women). The pain associated with it involves limitations in movement and represents a huge cost to society. Knee, hands, hip and spine are the most affected sites.

Arthritis is a degenerative inflammatory disease that affects the joints. It manifests itself with inflammation, pain and stiffness in the movements; until in the most serious cases the affected joints are deformed. There are various types of arthritis that arise for different reasons.

Patellar chondropathy (or chondromalacia) is quite common in sports and in the long run can lead to arthritis of the knee. The cause of origin is linked to the excessive stresses to which the knee is subjected during sports activity. Then there are a whole series of predisposing factors (such as muscular and articular imbalances) that contribute to the premature onset or aggravation of the pathology. Even acute trauma, like a fall, can contribute to its onset.

The patellar chondropathy affects the layer of protective cartilage behind the patella which wears out over time. In most cases it is asymptomatic but sometimes the subject complains of widespread pain around the kneecap associated with slight swelling (especially in severe cases).

Prevention of cartilaginous lesions

Cartilage, although poorly vascularized, is a living tissue that responds to external stimuli. In particular, the proliferation and functionality of the chondrocytes is regulated based on the mechanical stress suffered by the joint. If these stimuli fail, as happens following prolonged immobility (fracture), the production of proteoglycans slows down. And it is precisely from this consideration that the importance of regular physical activity in the prevention of osteoarthritis is evident.

Exercise also helps improve mood and appearance, reduces pain, increases elasticity and keeps body weight in check, improving balance and decreasing the risk of falls

The importance of physical exercise also derives from the consequent muscular reinforcement. Precisely this last point plays an important role in the prevention and treatment of patellar chondropathy. The strengthening of the quadriceps and in particular of the vast medial is very important for the patellar stabilization and the knee joint in general. It is performed thanks to a tool called leg extension working in the last degrees of extension with the tips of the feet facing outwards.

Also the diet has an important role in the prevention of cartilaginous lesions and if in the past someone has tried to draw up a whole series of useful and harmful foods today the general orientation is to propose a balanced and varied diet. The rules to follow are not specific for arthrosis but general pathology. It is therefore advisable to limit saturated fats, to prefer foods of biological origin, to take the right amounts of fiber, vitamins and minerals, as widely explained in the article: dietary advice.