Osteoarthritis- classification & diagnosis

Given the puzzling etiology of osteoarthritis, different classifications of the disease have been proposed, yet all coincide in making a clear distinction between primary or idiopathic osteoarthritis and secondary osteoarthritis. According to the American College of Rheumatology (ACR):
Idiopathic

- Localized (spine, knee, hip, hands, feet, elbow, shoulder, and other joints)
- Generalized (involving 3 or more joints)
Secondary
- Trauma
- Developmental and congenital diseases (dysplasia, etc.)
- Metabolic diseases (gout, etc.) - Endocrine disorders (diabetes, hypothyroidism, etc.)
- Calcium deposition diseases (pyrophosphate, hydroxyapatite, etc.)
- Other bone and joint diseases (rheumatoid arthritis, etc.)
- Neuropathic (Charcot) arthropathy
- Septic arthritis

- etc.
Diagnosis
Osteoarthritis is diagnosed by evaluating symptoms related to the location and characteristics of pain, the conditions under which it improves (rest) and worsens (when bearing a load), crepitus, and disorders in the axes of the lower limbs and the affected areas.

The symptoms of osteoarthritis depend on the joints affected, but have some characteristics in common. Symptoms begin gradually and progression is slow. At first, the pain appears when the joint is moved and goes away after rest. As osteoarthritis becomes more severe, the pain becomes more persistent. Pain usually appears after a period of rest until the joint warms up, and then reappears after prolonged exercise. Sometimes, as a result of rest and a lack of exercise, the muscles around the joints become atrophied, while on other occasions, the pain and bone deformations cause muscle contractures. In both cases, disorders in the muscles produce more pain, affect the normal mobility of the joint and result in a greater tendency for the disease to progress.

Radiographic studies make it possible to observe the characteristic changes caused by osteoarthritis in any location, as well as the intensity of those changes. The advantage of performing laboratory tests is that other diseases can be ruled out. It is always necessary for clinical symptoms to be present for radiographic tests to be useful. About 15% of people with disorders visible as a result of radiographic tests do not present with any discomfort.

Among others, the main signs and symptoms of osteoarthritis are:
Pain; restricted, painful movement
Stiff joints
Loss of mobility
A feeling of insecurity or instability
Functional impairment
Soft spots around the joint
Inflammation around the joint

Diagnosis of osteoarthritis is usually very simple. In general, the disease can be detected because of its clinical and radiological signs. The doctor can diagnose it based on the location and kind of pain, the situations under which it improves or worsens, and through a simple exploration of the joints affected. S

Methods used to detect the clinical manifestations of osteoarthritis include:

Measuring pain: pain can be quantified by the patient with the help of a scale using words (e.g.: no pain, minimal, moderate, severe, very severe), or by asking patients to evaluate the pain using the following scales:

- The most commonly used method at the present time is Huskisson’s Visual Analogue Scale (VAS), in which patients have to rate their level of pain from 1 to 10 or from 0 to 100.

- The WOMAC ( Western Ontario and McMaster Universities ) Osteoarthritis Index is also used because is has a section with five questions to be answered by patients to evaluate their own pain.
Measuring functional status: different indices are available, based on the location of osteoarthritis:
- Lequesne Algofunctional Index: indicated for gonarthritis and coxarthrosis. Consists of a questionnaire to be filled in by the patient with questions about pain and functional capacity.
- WOMAC Index: also contains a section to be filled in by patients to evaluate their functional capacity.

- Dreiser Functional Index for arthropathies of the hand: another questionnaire to be filled in by patients that includes questions on their ability to perform everyday hand movements.
There are other measurement tools that have not been validated but which are regularly used in practice to detect the clinical manifestations of osteoarthritis: measure of joint rigidity, inflammation, joint mobility, joint deformation, esthetic repercussions, functional impairment, quality of life and use of symptomatic treatments ( analgesics , NSAIDs, etc.).

Methods are also used to determine the progression of osteoarthritis in different joints:

Method developed by Gust Verbruggen to determine the progression of osteoarthritis in the finger joints. According to this scale, this progression can be determined by its evolution through previously described anatomical phases: “N” (not affected), “S” (classic osteoarthritis), “J” (loss of joint space), “E” (erosive osteoarthritis) and “R” (remodeled joint).

Method developed by Vignon et al. to determine the progression of osteoarthritis in the knee joints. It is based on the evaluation of the reduction in the articular space of the knee using quantitative radiology. X-rays are taken of both knees with the foot in the standard position and the knee in the Schuss position (flexed at 20%) at the beginning and after a certain amount of time. The X-rays are blindly analyzed using a validated digital image analysis system to observe the progression of: mean thickness, minimum width of the joint space and surface area.
Rheumatologists occasionally perform a series of tests to confirm the initial diagnosis and to gain an idea of the severity of the disease and its progression at the structural level. These tests may include:

Joint-fluid aspiration: The synovial fluid can be analyzed when viscosity is high and cellularity is low. This analysis is particularly useful for ruling out the existence of other inflammatory or microcrystalline processes.
Blood analysis: Blood disorders are not common in osteoarthritic patients, unless there is an associated disease. The sedimentation rate is usually normal except in cases of primary osteoarthritis, when it is moderately high. The results of systematic analysis (hemogram, urine, biochemistry parameters, etc.) are normal.
Radiology: In early stages, few or no disorders are detected, but the following symptoms gradually appear as the disease progresses:

- Narrowing of the joint space as a consequence of the loss of joint cartilage.
- Subchondral sclerosis, detected as an increase in bone density below the joint cartilage, the result of the reactive response of the bone.
- Osteophytes, the most specific symptoms of osteoarthritis. They are bone spurs the body produces and deposits in the osteoarticular area as a result of the new secondary bone formation due to constant stress on the joint bone.
- Subchondral cysts or geodes, which appear in intermediate stages of osteoarthritis.
- Luxations, joint dislocations that are found in advanced stages of osteoarthritis.

Other tests include: nuclear magnetic resonance (NMR), ultrasound, bone gammagram, CT scan, arthroscopy, etc.

A system of radiographic grading of osteoarthritis is also used. It was developed by Kellgren and Lawrence and is key in current radiological assessment of osteoarthritis:
Grade Classification Description of X-ray
0- normal no symptoms of OA
1- doubtful indications of osteophytes
2- minimal definite osteophytes
3- moderate moderate narrowing of joint space
4- severe joint space very narrow, subchondral bone loss