DISEASE CLASSIFICATION:
Osteoarthritis is classified as a degenerative disease. Degenerative diseases are caused by a deterioration of the body.
(Mace J.D & Kowalczyk N.,2004)
ETIOLOGY (CAUSE) :
- Primary osteoarthritis is mostly related to aging. With aging, the water content of the cartilage increases, and the protein makeup of cartilage degenerates. Eventually, cartilage begins to degenerate by flaking or forming tiny crevasses.
- Secondary osteoarthritis is caused by another disease or condition. Conditions that can lead to secondary osteoarthritis include obesity, repeated trauma or surgery to the joint structures, abnormal joints at birth (congenital abnormalities), gout, diabetes, and other hormone disorders.
- Obesity causes osteoarthritis by increasing the mechanical stress on the cartilage. Obesity is the most powerful risk factor for osteoarthritis of the knees next to aging.
- Crystal deposits in the cartilage can cause cartilage degeneration and osteoarthritis. Uric acid crystals cause arthritis in gout, while calcium pyrophosphate crystals cause arthritis in pseudogout.
- Some people are born with abnormally formed joints (congenital abnormalities) that are vulnerable to mechanical wear, causing early degeneration and loss of joint cartilage.
- Hormone disturbances, such as diabetes and growth hormone disorders, are also associated with early cartilage wear and secondary osteoarthritis.
(Shiel W. C. Jr, 2008)
Who are at risks:
- Among the over 100 different types of arthritis conditions, osteoarthritis is the most common, affecting over 20 million people in the United States.
- Osteoarthritis occurs more frequently as a person gets older. Before age 45, osteoarthritis occurs more frequently in males.
- After age 55 years, it occurs more frequently in females.
- In the United States, all races appear equally affected. A higher incidence of osteoarthritis exists in the Japanese population, while South African blacks, East Indians, and Southern Chinese have lower rates.
Pathogenesis (sequence of event):
- In healthy cartilage, continual internal remodeling occurs as the chondrocytes replace macromolecules lost through degradation. This process becomes disrupted in osteoarthritis, leading to increased degenerative changes and an abnormal repair response.
- In the early stages of OA, the chondrocytes attempt to compensate for this imbalance by producing increased quantities of proteoglycans and collagen.
- This may lead to an initial thickening of the articular cartilage and enable the joint to maintain normal function for years; however, the quantity and quality of the proteoglycan and collagen produced are not normal.
- Some components of the matrix are overproduced and the quality of the proteoglycans resemble immature fetal forms
- Eventually, the arrangement and size of collagen fibers are altered and the proteoglycans begin to break down faster than they can be synthesized.
- The decreased proteoglycan content and altered collagen structure of the matrix result in a deterioration of the cartilage's normal physiologic properties.
- Early damage to the cartilage may consist of microfractures and fibrillations.
- As OA progresses, gross evidence of damage to articular cartilage becomes evident. The normally smooth surface of the cartilage becomes rough or eroded with cracks. The cartilage may also show signs of chondromalacia due to the increase in the ratio of water to proteoglycan in the cartilage matrix.
- Moreover, cartilage erosions (ulceration with exposure of underlying bone) can be seen in more severe OA.
(Hinton R., 2002)
Manifestation (observe changes)
Sign:
- Knobby bony deformity
o A very common early sign of osteoarthritis is a knobby bony deformity at the smallest joint of the end of the fingers called Heberden's node.
o The bony deformity is a result of the bone spurs from the osteoarthritis in that joint.
o Another common bony knob (node) occurs at the middle joint of the fingers in many patients with osteoarthritis and is called a Bouchard's node.
- Swelling
o Arthritis can cause swelling in joints, making them feel tender and sore.
· Deformed joints
o Joints can start to look like they are the wrong shape, especially as arthritis gets worse
(Shiel W. C. Jr, 2008)
Symptoms:
- Pain
o Joints may ache, or the pain may feel burning or sharp. For some people, it may get better after a while.
o Pain while sleeping or constant pain may be a sign that arthritis is getting worse.
- Stiffness
o When you have arthritis, getting up in the morning can be hard.
o Joints may feel stiff and creaky for a short time, until get moving.
o May also get stiff from sitting.
- The muscles around the joint may get weaker
o This happens a lot with arthritis in the knee.
- Cracking and creaking
o Joints may make crunching, creaking sounds.
- Limited range-of-motion
(Parks R., 2007)
DIAGNOSTIC TEST AND PROCEDURES:
- Significant Lab Test:
There is no specific laboratory test to diagnose OA. Blood tests are performed to exclude diseases that can cause secondary osteoarthritis, as well as to exclude other arthritis conditions that can mimic osteoarthritis.. Tests that may be ordered to rule out other conditions and to evaluate the patient’s health include:
- Rheumatoid factor (RF) and Cyclic Citrullinated Peptide Antibody (CCP)
o Used to help diagnose rheumatoid arthritis and differentiate it from osteoarthritis.
- Synovial fluid analysis
o To detect crystals that may be present in the joint and to look for signs of joint infection.
- Erythrocyte sedimentation rate (sed rate or ESR)
o This test shows the presence of inflammation in the body. ESR will be increased in RA but not in osteoarthritis.
- C-reactive protein test (CRP)
o This test also indicates inflammation and tests for the activity of the disease.
o It may be used to help differentiate osteoarthritis and RA.
o An increased level of CRP occurs in RA but not in osteoarthritis.
- Complete Blood Count (CBC)
o This is a group of tests that are used to help evaluate the patient’s red and white blood cells and hemoglobin.
o It may be ordered to monitor the side effects of some OA treatments.
- Comprehensive Metabolic Panel (CMP)
o This is a group of tests that may be used to help evaluate and monitor the patient’s kidney and liver function.
- Arthrocentesis
o Often performed in the doctor's office.
o During arthrocentesis, a sterile needle is used to remove joint fluid for analysis. Joint fluid analysis is useful in excluding gout, infection, and other causes of arthritis.
o Removal of joint fluid and injection of corticosteroids into the joints during arthrocentesis can help relieve pain, swelling, and inflammation.
(Shiel W. C. Jr, 2008)
Imaging procedure
Imaging Consideration:
- Weight Bearing Technique
o Films obtained during weightbearing or varus and valgus stress are necessary in early stages of osteoarthrosis of the knee joint.
o Ideally, the weightbearing radiographs should be obtained with a patient standing only on the involved leg in 15 to 20 degrees of knee flexion.
o Additional exposures using other degrees of knee flexion may be necessary to demonstrate the loss of joint space, especially in the lateral compartment.
o With the knee in extension, early joint space loss may not be seen .
o The weightbearing technique also allows more accurate delineation of subluxation, varus or valgus angulation, and lateral instability.
(Bontrager K.L, lampignano J.P. 2005)
o Exposure Factor (Decrease)
o Osteoarthritis causes the affected body tissue to decrease in thickness, effective atomic number, and density.
o There will be less attenuation of the x-ray beam.
o As more photon are able to pass through the body tissue, more will be available to reach the image receptor.
o This disease is easier to penetrate and called as destructive condition.
o They require decreasing the exposure to achieve he proper image receptor exposure.
(Carlton R.R.& Adler A. M.,2006)
Figure: the knee radiograph show mild OA
- CT Scan
o Doctor may want to order a CT if the standard radiograph images are not clear or a three-dimensional view of a particular joint is needed, such as when viewing the knee.
o CT images will show similar findings as standard radiographs, but with much greater detail and depth of the bones.
o Smaller bone spurs and more subtle signs of bone erosion and sclerosis may be easier to identify with CT than with standard radiographs.
o Again, when to choose this form of study depends on each individual patient’s situation and specific considerations. CT scans do emit radiation to the body and so the risks and benefits to each patient must be weighed.
Figure: knee coronal plane Ct-scan show OA
- Radionuclide Bone Scans
o Radionuclide Bone Scans are very sensitive in detecting reactive bone edema association with osteoarthritis.
o Bone scans can also image the entire skeleton in one examination and thus can provide the clinician with helpful information in patients who there are multiple sites of arthritic involvement
- MRI
o There is no radiation involved in MRI and it sees most structures which not seen by x-ray.
o Its value for the diagnosis of osteoarthritis of the knee is somewhat limited.
o The MRI is most useful for patients with very early osteoarthritis of the knee.
o For people who have knee pain without injury and who have not responded to cortisone shots or anti-inflammatory medicines, the MRI can detect a meniscus cartilage degeneration that cannot be seen on x-ray.
o Meniscus cartilage is a c-shaped shock absorber on each side which can become dried out and crumble as part of the process of osteoarthritis.
(Chester V., 1996)
Figure: T1-weighted coronal MRI of the knee shows typical findings of osteoarthritis, including narrowing and subchondral changes at the medial femorotibial compartment and osteophyte formation.
