Definition and pathogenesis of Osteoarthritis
Primary osteoarthritis is the most frequent joint disorder. It affects all joint tissues, predominantly the articular cartilage, the adjacent subchondral bone, the synovial membrane, but also the menisci, the ligaments, and the joint capsule. The following are considered to be risk factors: family history of osteoarthritis, age, obesity, malalignement of the joints and female gender. There is a mismatch between tissue maintenance and degeneration at the beginning of the disease process. The eventually reduced quality of articular cartilage leads to a physical breakdown of the formerly smooth surface releasing micro particles into the joint cavity, which in turn provoke a mild inflammation in the synovial membrane. The bone undergoes a remodeling process at the edges and in the subchondral area. Osteoarthritis is generally a slowly progressing disease which leads gradually to a reduction in joint function. The range of motion may be limited and instability leads to painful overstrain of the ligaments.
Primary osteoarthritis affects typically the knees, hips, the metatarsophalangeal joins of the big toe, the first metacarpophalangeal joint of the thumb, the proximal and distal interphalangeal joints of the fingers, and the facet joints of the cervical and lumbal spine (see picture).
Secondary osteoarthritis resembles primary osteoarthritis in its clinical presentation. However, secondary osteoarthritis is the result of any preceding joint-destructive process such as primary inflammatory arthritis, joint-fractures or metabolic arthropathies. Secondary osteoarthritis may affect any joint of the body.
Pain is the leading symptom of osteoarthritis. Classically, the pain is strain-induced. In the weight bearing joints, pain is most intense for the first couple of steps after resting, eases eventually and increases again with ongoing physical activity. During inflammatory phases, the joints become swollen, warm and tender to touch. The pain may then be constantly present. The joints may feel stiff in the morning for only a couple of minutes. In advanced disease, the range of motion becomes limited due to bony alterations; the affected joint loses its stability hindering activities of daily life.
The diagnosis can be made with a thorough patient’s history and physical exam alone. If in doubt, imaging studies may support the diagnostic process. The calcified tissue may be very well evaluated in standard X-rays. Ultrasound allows for an evaluation of inflammatory activities. MRI-studies, finally, depict any tissue within a joint and may be especially helpful in the assessment of the patellar cartilage, the menisci, the cruciate ligaments, and also the inflammatory activity. Routine blood tests show usually results within normal limits. The inflammatory markers, however, may be slightly elevated during inflammatory phases. Laboratory analyses are primarily of help in ruling out other joint diseases than osteoarthritis. If the pain source is suspected to be located within the articular bone, specific blood test to assess bone metabolism may be necessary. Synovial fluid presents with typical characteristics, such as a low leucocyte count, and is also mainly of help to rule out other or concomitant disease such as gout.
Informative material is part of the therapeutic strategy to teach the patient how to protect the osteoarthritic joint, how to support the regenerative potential by moderate physical activity and to inform about the natural course of the disease. Ergotherapy is further helpful to instruct the patient face to face in joint protection. Physiotherapy helps strengthen the muscles of the affected region to compensate instability. In addition, physiotherapy can provide pain relieve with massages, electrotherapy, and application of heath and therapeutic ultrasound. Joint-tissue maintenance is supported by neutraceuticals such as Vitamin D, Vitamin C, Calcium, Chondroitin sulfate and Glucosaminesulfate. Pain relieve is best obtained with non-steroidal anti-inflammatory drugs (NSAIDs). Overstrain of collateral ligaments and tendon insertion sites may respond very well to NSAID-crèmes instead of pills. In case of an acute inflammatory phase, glucocorticoids can be injected directly into the joint cavity to provide rapid anti-inflammatory activity and pain-relieve. Intra-articular injections of Hyaluronic acid provide not as fast a pain relieve as seen in glucocorticoids, but are known for a sustained effect which exceeds the glucocorticoid-effect. And finally, an autologous blood product, platelet rich plasma (PRP), has been shown to attenuate the inflammatory joint activity and to relieve symptoms. In case of a predominantly inflammatory phenotype of osteoarthritis, such as the erosive form of osteoarthritis of the hands, a disease modifying antirheumatic therapy (DMARD) may be used as in Rheumatoid Arthritis. Orthoses and braces may be helpful in unstable osteoarthritic joints. The therapeutic endpoint is considered to be joint surgery, e.g. osteotomy, joint replacement surgery, or joint fusion. Arthroscopic joint lavage is no longer indicated for Osteoarthritis.
The treatment plan is arranged on an individual basis taking into account the degree of suffering, the predominant disease characteristics, and the stage of the disease to meet the patients’ specific needs.