Mauro Keiserman, MD. Rheumatology Specialist by the Brazilian Society of Rheumatology.
Synonyms: osteoarthrosis, osteoarthritis, degenerative joint disease.
What is it?
It’s the most frequently found joint disease, and the cartilage is the tissue initially altered. The cartilage is attached to the surface of the bones that articulate with each other. It’s formed by a tissue rich in proteins, collagen fibers and cells.
How does it develop?
Osteoarthritis (AO) begins when some protein constituents undergo change, while others decrease in number or size. There’s an attempt at repair through proliferation of cells of the cartilage, but the outcome from the balance between destruction and regeneration is a cartilage that loses the smooth surface that allows bone surfaces to properly glide on.
This process is accompanied by a release of enzymes that usually are inside the cartilaginous cells. The action of these enzymes cause a local inflammatory response, which enhances the tissue lesion. Erosions appear on the articular surface of the cartilage, which seems full of small craters. The disease development leads the adjacent bone to be compromised, presenting fissures and cysts.
At the same time, as if attempting to increase the contact surface and achieve greater stability, the bone grows. But this is not a normal bone, being stiffer and more susceptible to microfractures that take place chiefly in weight-bearing joints.
Apparently, due to the local inflammatory response, every element of the joint undergoes hypertrophy: capsule, tendons, muscles and ligaments. The joints undergo an increase in size and may present local warmth.
The level of compromising greatly varies. The disorder can evolve until the destruction of the joint, or stall at any moment. There are individuals with deformities in the fingers and toes who have never experienced pain, while others will experience pain and a progressive aggravation of the disease with consequent deformity and decreased joint function.
What initially triggers osteoarthritis is not known. Different mechanisms are believed to lead to similar changes in the function and composition of articular structures.
The disease becomes evident from age 30. It is estimated that 35% of people already have osteoarthritis in some joint by this age, the vast majority being asymptomatic. The knees and the spinal column are the most affected sites. At age 50, prevalence greatly increases, and from age 70, 85% of the individuals will present radiographic changes.
Osteoarthritis (AO) in the fingers is more frequent in women and shows a high family incidence, favoring a genetic mechanism.
Osteoarthritis in joints subject to strain, such as hips and knees, is more frequent in obese people; the same may happen to the spinal column.
Postural defects- as bow legs or knocked knees favor osteoarthritis of the knee. An inadequate position of the femur in relation to the pelvis induces to cartilage degeneration in specific sites of the coxofemoral joint.
Similarly, foot defects will lead to the onset of osteoarthritis, bunion being the best example. However, there are patients suffering from another type of osteoarthritis in the great toe that is not related to any postural defect.
Joint hyperelasticity – most common in women, it may allow joint surfaces to go beyond their anatomic limits, and the cartilage, gliding on hard surfaces, undergoes erosion. Osteoarthritis between the femur and the patella (femoropatellar joint) is a common example.
Metabolic diseases as diabetes and hypothyroidism favor the development of osteoarthritis.
Other diseases that affect the cartilage, as rheumathoid arthritis, infectious arthritis and crystal deposition disease (gout and chondrocalcinosis) may present with the same kind of injury and are labeled as secondary osteoarthritis.
What does one feel?
Prior to pain, osteoarthritis patients may complain about articular discomfort or discomfort around the joints, and tiredness. Subsequently, pain appears, followed, later, by deformities and restriction of the articular function. In the beginning, pain emerges after a prolonged use of the compromised joints or strain on these.
Afterwards, patients complain that following a long period of inactivity, such as sleeping or prolonged sitting, in cases of hip or knee osteoarthritis, pain is experienced in the beginning of the motion, remaining for a few minutes.
Examples are discreet pain and stiffness in the fingers and knees that last a few minutes in the morning, or after sitting for a while. In patients with progressive aggravation, pain becomes stronger and longer, and deformities accentuate.
In hip and knee osteoarthritis, climbing or descending stairs is made harder, as well as longer walks.
Inflammation may produce an increase in the synovial fluid. In these situations, pain increases, motions become more restrained, and joint palpation demonstrates local warmth, in addition to the presence of fluid accumulation.
It’s believed that the fact alone of a joint being compromised is enough for the development of muscle atrophy, but, certainly, the lack of full motions and inactivity are significant adjuvant factors. In extreme cases, patients need to use canes or crutches. A hip and knee osteoarthritis patient seldom ends up on a wheelchair.
Osteoarthritis of the hands
It’s more frequent in women. There may be an exclusive compromising of joints near the nails (distal interphalangeal joints). After a slow development that isn’t necessarily accompanied by pain and redness, these joints start presenting hard bony spurs of irregular distribution.
Less frequently, similar injuries may occur to proximal interphalangeal joints. Grip ability may become highly impaired.
A usually involved site is the joint below the thumb (trapeziometacarpal joint). Often, this joint, in both hands, is the only one involved.
Severity is quite variable. It may not affect the function of the hands, but there are cases of dislocation of the thumb to the palmar region and strong pain on holding objects.
Osteoarthritis of the feet
Bunions are commonly found. They’re the result from a defect in the position of the bones that form the joint between the great toe and the midfoot.
Osteoarthritis is resultant from the wear of the cartilage and the adjacent bone, and consequent abnormal bone growth. The attrition caused by wearing shoes forms a bursa (cyst under the skin) that becomes inflamed and aches.
A number of postural defects or defects in the foot mechanics that aren’t corrected with appropriate shoes, exercises, insoles, or surgery, lead to cartilage lesions, and, thus, osteoarthritis. The feet may become greatly deformed and stiff, making it hard to walk and wear shoes.
Hip osteoarthritis (coxarthrosis)
Most coxarthrosis cases are secondary to early acquired or congenital defects in the pelvis or femur.
When the two joints are involved, obesity must be an important factor. Pain may be located in the groin, buttock, external or internal part of the thigh, and, less frequently, it can radiate or be restricted to the knee only. In all cases, there will be a progressive limitation in the motions of the thigh, with difficulty putting on shoes and pants being common.