Osteoarthritis of the knee (gonarthrosis)

The knee joint consists of three anatomical parts (compartments): the tibiofemoral (tibiofemoral) section, which has medial and lateral areas, and the patellofemoral (patellofemoral) section. Each of these areas can be affected by osteoarthritis separately, or any combination of lesions is possible. The most common are isolated osteoarthritis of the knee joint in the medial tibiofemoral section and combined lesions of the medial tibiofemoral and patellofemoral sections.

On average, the medial tibiofemoral region is affected in 75%, the lateral tibiofemoral region in 26%, and the patellofemoral region in 48% of cases.

Articular cartilage loss is usually most pronounced in the lateral patellofemoral compartment and on the articular surface of the tibia in the tibiofemoral compartment, the area least covered by menisci. According to arthroscopy and MRI, in addition to articular cartilage damage, gonarthrosis also affects the menisci. Osteophytosis is most pronounced in the lateral tibiofemoral compartment, while maximum cartilage destruction is usually found in the medial compartment.

The biomechanics of the knee joint is well studied. In a normal joint, the load axis passes through the center of the tibiofemoral region. However, during movements when the load on the tibiofemoral region is 2-3 times greater than the body weight, the maximum load falls on the medial part of the joint; when the knee joint is flexed, the load on the patellofemoral part is 7-8 times greater than the body weight. Perhaps this explains the high frequency of damage to the medial tibiofemoral and patellofemoral regions of the knee joint. The development of gonarthrosis is facilitated by some physiological anomalies of the knee joint - physiological genu varum, joint hypermobility, etc. Meniscectomy and damage to the ligamentous apparatus disrupt the normal distribution of the load on the knee joint, which is a predisposing factor to the development of secondary gonarthrosis.

Patients with osteoarthritis of the knee joint can be divided into two groups. The first group includes young patients, more often men, with isolated lesions of one, less often both knee joints, with a history of trauma or surgery (for example, meniscectomy) on the knee joint. The second group includes middle-aged and elderly people, mainly women, who have osteoarthritis of other localizations at the same time, including the hands; many patients in this group are obese.

The most important symptoms of gonarthrosis are pain in the joint when walking, standing for a long time and going down the stairs; crunching in the joints when moving; localized pain on palpation, mainly in the medial part of the joint along the joint space; painful limitation of flexion and later extension of the joint, marginal bone growths, atrophy of the quadriceps femoris. Damage to the medial part of the knee joint leads to the development of varus deformity. Rarely occurring damage to the lateral part of the tibiofemoral joint can cause the formation of valgus deformity. With any type of damage, osteoarthritis of the knee joint often shows signs of inflammation. In this case, the nature of the pain changes: the pain intensifies, "starting" pain, pain at rest, morning stiffness in the joint lasting up to 30 minutes appear. A slight swelling and a local increase in skin temperature appear in the joint area. Due to the presence of a bone or cartilage fragment (“joint mouse”) in the joint cavity, a patient with gonarthrosis may experience symptoms of a “blockade” of the joint (acute pain in the joint, depriving the patient of the ability to make any movement).

Factors associated with the progression of gonarthrosis (according to Dieppe PA, 1995)

• Old age
• Female gender
• Overweight
• Generalized osteoarthritis (Heberden's nodes)
• Diet deficient in antioxidants
• Vitamin D Deficient Diet/Low Plasma Vitamin D

The course of osteoarthritis of the knee joint is long, chronic, progressive, with a slow increase in symptoms, often without sharply expressed exacerbations. In some patients, gonarthrosis can proceed stably both clinically and radiographically for many years. Spontaneous decrease in the severity of symptoms may occur periodically. Unlike coxarthrosis and osteoarthritis of the hand joints, spontaneous improvement (reversal) of radiographic signs of osteoarthritis occurs extremely rarely. Osteoarthritis of the knee joint most often proceeds with periods of "exacerbation", which are usually accompanied by the appearance of effusion in the joint cavity and last for days/months, and improvement, or "remission". In some cases, deterioration of the disease occurs over several weeks or months. This may be due to the development of joint instability or destruction of the subchondral bone. Sudden, almost instantaneous pain in the knee joint may indicate the development of aseptic necrosis of the medial femoral epiphysis - a rare but severe complication of osteoarthritis.

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