This covers inflammation, degenerative changes of articular cartilage, pathological changes in other parts of the joint, as well as pain and damage of the function.
Articular cartilage, although being only a few millimetres in size, can bear the maximum load, which is several times heavier than the body weight. This biomechanical quality of cartilage is due to hydroelastic system, which is based on the high water binding capacity in its structure and basic architecture of its collagen fibres network. During loading of the cartilage the water is extruded and it enters the synovial space (inner joint membrane) but during the relief of the loading the liquid is sucked back into the cartilage. Along with the absorption of pressure, the characteristic of articular cartilage is facilitating mutually sliding joints, plus it does not contain blood vessels and nerves, and has the ability to repair.
Osteoarthritis or arthrosis is an inflammatory disease of the joints that occurs due to interaction between mechanical and biological events. Its development incurs degenerative changes in the articular cartilage, which then cause pathological changes in other parts of the joint, all of which eventually lead to pain and damage to the joint function (Figure 1).
After cardiovascular diseases, osteoarthritis is the second most common cause of a chronic work incapacity. Its extent is evident by the fact that, in developed countries in 50 percent of all people over the age of 40, osteoarthritic changes in bones and joints may be proven morphologically, but at that age they still don’t manifest clinical symptoms. Over the years the process progresses, so 75 percent of 75-year-olds have a cartilage damage and osteoarthritis (Figure 2). Arthritic changes are three times more common in women than in men. Out of all large joints in humans these changes are most often found in the knee joint.
There are many factors that lead to the osteoarthritis development. Although aging is considered to be among the main risk factors, the research shows that osteoarthritis is not an inevitable part of aging. Obesity is a risk factor for developing osteoarthritis in knees. There is an increased risk of developing osteoarthritis in people with sports injuries, injuries at work and other accidents.
Gradual but steady development of symptoms
The degree of cartilage degeneration can be divided into four stages (Figure 3):
- Intact cartilage
- Early degenerative changes
- Advanced degenerative changes
- Final stage of degenerative changes
Clinical symptoms develop slowly and depend on the stage of the disease. The first sign of the disease is usually a dull, gradually emerging pain after sleep. Clinical examination can establish joint pain on palpation, crepitations during movement, decreased motion range, deformity of the joints (osteophytes), swelling disorder (haemorrhage) and muscle weakness.
Radiological findings – confirmation of clinical suspicion
The progress stage of the disease influences the therapeutic approach
It consists of an application of anti-rheumatic drugs and analgesics (painkillers). This approach is based on the possibility that drugs, modifying the structure of cartilage, affect the speed of the disease progress, hence it is suitable for treatment of early stages of cartilage damage. This means that anaesthetics and corticosteroids are applied locally to the joint. Due to the adverse cumulative effects of corticosteroids, doctors prefer to use them far less than patients and resort to this only when they have no other choice, i.e. when other, less harmful methods fail in achieving an improvement. Given that the process of cartilage damage in all phases is characterized by a progressive decrease of hyaluronic acid concentration in the synovial fluid; hyaluronic acid may be injected in the knee to achieve a visco-supplementation. A hyaluronic acid is a physiological component of the synovial fluid, cartilage, and connective tissue of the human body. Its production in synovial joints decreases throughout life, so the majority of people at the age of 50 has 50% less hyaluronic acid in the knee joints than they had in their youth.
The role of synovial fluid is to protect and lubricate joints, and to enable cartilage nutrition. The synovial fluid of each synovial joint is secreted by a synovial capsule membrane of the joint capsule which continuously produces hyaluronic acid as well. A hyaluronic acid forms a continuous network in a synovial fluid and it enables its viscous properties, plus, having high water-binding capacity, it lubricates articular surfaces during the movement thus absorbing motion. By coating pain receptors in the synovial membrane, it reduces painful response of the joint and relieves pressure forces in the cartilage resulting from load, body weight and movement of the joint.
This approach will be selected by an orthopaedic surgeon only when all other non-surgical treatment methods have failed. The doctor and the patient will then choose the type of surgery, according to osteoarthritis type, severity, and patient’s physical condition. A surgical treatment includes an arthroscopic shaving of the joint, which enables processing of menisci with degenerative changes, removal of altered cartilage, with drilling or abrasion of joints bodies (microfracture), thus stimulating the formation of fibrocartilage repair on the spot of the complete cartilage loss (Fig. 5 and 6).
In the case of deeper cartilage damage, along with subchondral bone (bone area beneath the cartilage area), the mosaicplasty may be recommended (Figures 7, 8 and 9). It is a process in which the cartilage is transplanted along with subchondral bone from healthy cartilage place onto the damaged place.
A corrective osteotomy may be performed in cases of a mild and moderate arthritis, as a preventive procedure to slow down the progression of arthritis and correct deformities or a bad joint shaft, thus relieving the damaged part of the joint or the cartilage. In advanced stages of arthritis in the elderly, the treatment of choice is arthroplasty (artificial joint). In cases of a severe osteoarthritis an orthopaedic surgery can often relieve pain and restore a lost joint function. A total joint replacement usually enables a person with severe osteoarthritis of the hips or knees to walk without pain or stiffness.