Osteoarthritis refers to a pathological process characterized by dystrophy and degeneration of the articular cartilage. As a rule, the issue is not limited to cartilage alone - later the pathology spreads to the bone (subchondral) tissue located under the cartilage. Therefore, osteoarthritis is also called osteoarthritis. And since all of these disorders ultimately lead to a change in the structure of the joint, this process is called deforming osteoarthritis, which can affect any joint. In clinical practice, in most cases, osteoarthritis of the knee joint or knee osteoarthritis is noted.
The essence of pathology
In terms of frequency and prevalence, osteoarthritis of the knee comes right after osteoarthritis of the hip (coxarthrosis). To find out what caused this, it is worth looking briefly at the features of the anatomical structure of the knee and the functions it performs. It is one of the most massive joints, in the formation of which 3 bones are involved - the femur, tibia and kneecap. Thus, it is a complex joint formed by 2 joints - the patellofemoral and patellofemoral joints.
The articular surfaces of all 3 bones are covered with cartilage, which facilitates movement of the joint and protects the subchondral bone tissue from mechanical wear. In addition to the articular cartilage itself, the knee exhibits menisci - paired cartilage formations that improve the congruence (anatomical match) of joint surfaces. Articular cartilage does not have its own blood vessels. Its nutrition is diffused from the intra-articular (synovial fluid). Like a sponge, cartilage contracts under mechanical stress during movement, supporting heavy loads. At this time, the waste is released from the cartilage tissue into the surrounding synovial fluid. On the contrary, at the time of relaxation, rest, the synovial fluid and the nutrients it contains enter the cartilage of the knee.
For a number of reasons, the nutrition of the articular cartilage of the knee joint is disturbed, resulting in osteoarthritis of the knees. At the same time, at the beginning there is a deficiency of nutrients in the cartilage tissue - chondroitin sulfate, glucosamine, calcium and other microelements. Moisture is lost. This is a process of dystrophy, followed by degeneration - thinning of the articular cartilage. In turn, these negative processes lead to structural and motor disorders in the knee joint.
Osteoarthritis of the knee is often confused with salt deposition. Let's say that some mineral salts, including table salt, are deposited in the form of microcrystals in the joint cavity, which causes pain and movement disorders. This is not true. Apparently, a completely different process is used for the deposition of salts. In response to the destruction of articular cartilage in the subchondral bone, marginal bony growths - osteophytes - form in order to stabilize the knee at least to some extent. However, in the future, osteophytes only aggravate osteoarthritis and contribute to the subsequent destruction of cartilage.
Causes
The causes of osteoarthritis of the knee joint are diverse and may be due to the pathology of the knee itself, or to other diseases and metabolic disorders. In this regard, knee osteoarthritis can be primary and secondary. The mechanism of primary osteoarthritis is not fully understood. It is believed that in this case, the disease is caused by a combination of factors, including:
- Advanced age, when degenerative changes occur not only in the articular cartilage, but also in all organs and tissues;
- Overweight, which increases the mechanical stress on the joint;
- Physical inactivity, or vice versa, excessive physical activity;
- Certain congenital anatomical disorders of the knee, in which the articular cartilage and the subchondral bone are initially impaired;
- General metabolic disorders leading to a change in the mineral composition of the synovial fluid.
Secondary osteoarthritis of the knee joints is a complication of other diseases. Most often such diseases are arthritis of a diverse nature - gouty, rheumatic, rheumatoid, septic, tuberculous, etc. In these diseases, various pathological factors (infection, perverted immune reactions, uric acid crystals) form inflammation of the synovial membrane in the form of so-called. synovitis. Synovitis is necessarily accompanied by a deterioration in the quality of synovial fluid, which in turn leads to osteoarthritis.
Another common cause of osteoarthritis is knee injuries. Post-traumatic osteoarthritis of the knee joint is a consequence of an intra-articular fracture of the femur and tibia, hemarthrosis (joint hemorrhage), injury to the ligaments of the knee and menisci. Here the pathology is based on a mechanical factor (damage) and damage that develops afterwards (arthritis). In addition, osteoporosis is often accompanied by osteoarthritis. Deficiency of calcium in the bones leads to destruction not only of bones, but also of cartilage tissue.
Symptoms
The main symptoms of osteoarthritis of the knee joint:
- Pain;
- Impaired knee movement;
- Difficulty walking;
- Crackling when moving;
- First - pathological tension, then - muscle atrophy of the lower limb;
- Deformation of the knee joint.
At first, as a rule, the patellofemoral joint suffers, which accounts for most of the functional load. In general, knee pads with osteoarthritis are perhaps the most vulnerable. It is from the cartilage of the kneecap that dystrophic changes begin in osteoarthritis. Clinically, this manifests as swelling and pain when feeling this bone. As a result of dystrophic changes, the articular cartilage undergoes sclerotic changes - it loses its elasticity and is replaced by coarse connective tissue.
Subsequently, the articular bag and the ligamentous apparatus undergo sclerotic changes. The configuration of the joint changes. Initially, due to concomitant arthritis, it is swollen, inflamed. Subsequently, with the progression of degeneration and sclerosis, the amount of synovial fluid decreases sharply, the joint space narrows, which inevitably leads to movement disorders. At first, the gait is difficult and the muscles of the limb are tense. Then ankylosis develops - complete immobility of the knee and, as a result, atrophy of the muscles of the thigh and lower leg. All of these changes take shape over a long period of time. In this regard, there are 3 degrees of osteoarthritis:
- Osteoarthritis of the knee joint of the 1st degree. The pain is localized mainly in the area of the kneecap and along the inner surface of the knee joint. The pains are of a "beginner" nature - they appear at the beginning of the movement, then subside. In addition, the pain can appear with a great effort (long walk, weight bearing) and disappear after rest. There are no structural changes in the joint at this stage.
- Osteoarthritis of the knee joint of the 2nd degree. Pain can occur even at rest and bother for a longer time. Limitations in range of motion (contractures) appear in the knee. The patient limps, has to move with a stick. Inflammatory and dystrophic changes in the joint are formed, manifested externally as an increase in the knee due to edema.
- Third degree osteoarthritis of the knee joint. Severe knee pain that does not stop even after a long rest. Serious and irreversible disorders of the structure of the joint, leading to ankylosis and loss of the ability to move. Modification of the configuration of the entire lower limb, manifested by its curvature in valgus or varus (O or X).
The diagnosis of osteoarthritis of the knee is made on the basis of the above symptoms and complaints of the patient, as well as x-ray data (narrowing of the joint space, osteophytes, osteoporosis, hardening of the bone). Knee osteoarthritis is treated in a complex with the use of drugs and physical procedures. With 3rd degree osteoarthritis, surgery is indicated, during which various types of plastic of the knee joint are performed.