Osteoarthritis Causes and Risk Factors
Osteoarthritis is a chronic disease with multiple factors proposed to be responsible for it. There are different ways the following factors can lead to the pathological changes seen in osteoarthritis.
Age
Osteoarthritis is viewed as one of the classical diseases of old age. It is also important to mention that the rise in osteoarthritis that is seen, has a causal relationship with increasing age, as the age dynamics continue to improve with feats in medical and surgical fields.
There are a variety of ways by which aging can predispose to osteoarthritis. One of the most simple and self-explanatory is the musculoskeletal changes. With increasing age, natural wear and tear sets in with a compromised ability to regenerate damaged tissue. When this gets coupled with other factors like injury and insult, it is a breeding ground for osteoarthritis. Older people also have more stores of cumulative lifelong stress, oxidative damage, delayed healing etc.
The incidence of osteoarthritis increased with age significantly in the 60s. According to a study, patients over 65 make 43% of the total under study. However, as it is a slowly progressing disease, it may set in earlier than the 40s and only be diagnosed after significant damage later in life.
Female gender
Another important trend in osteoarthritis is linked with gender. Various studies confirm a stronger disposition in females, particularly after the menopause. Also, there has been a link to the type and location of joints that are more commonly involved in females suffering from osteoarthritis. Hip and knee are the key weight-bearing joints which are most commonly affected in females. A part of this fact can be attributed to the natural anatomical structure of the female pelvis. A wider pelvis can contribute to lifelong stress on these joints. A very important factor can be childbearing, which not only compromises bone-health of females, but also is an additional burden on these joints.
The link with the menopause further hints at the hormonal role in the development of osteoarthritis. This is further confirmed on the basis of research which says that post-menopausal women on estrogen-replacement therapy lowers their chances of getting osteoarthritis by 15%.
Estrogen plays a key role in bone health of females. With the loss of estrogen, the bone health deteriorates, again predisposing females to this disease. This is why the incidence of osteoarthritis increases after 45 years of age in females as compared to their male counterparts. Unfortunately, it is not only common, but also is marked with more severity of symptoms. Lifestyle practices, gender-based job preferences, naturally-selected gender roles, and even underlying changes in metabolic and biological structure are held responsible for this trend.
Obesity
With the rise in the modern epidemic of obesity and promising longevity of life, the incidence and prevalence of osteoarthritis does not seem to decline, rather it is expected to rise. Studies have established a significant link between obesity and osteoarthritis with people having a BMI greater than 30 being 6.8 times more prone to developing osteoarthritis in late adulthood. Obesity related OA is also statistically more common in females.
Particularly, the knee joint is seen to be most affected in obese patients, with the incidence of hip joint not being significantly linked. This can be due to the high stress, and weight load that obesity puts on the respective joints. However, obesity does not only cause joint stress via mechanical strain. It also alters the metabolic and inflammatory pathways, healing mechanisms. The fact that obesity exposes to other co-morbid conditions cannot also be ignored.
What metabolic pathways lead to osteoarthritis in obese patients cannot be declared with certainty. However, the studies have reported a metabolic change with a greater number of adipokines in obese patients. These adipokines are chemical with their receptors on multiple surfaces, including parts of the joint, cartilage and synovium. These chemicals can initiate inflammatory processes in the same manner as explained in the pathophysiology of osteoarthritis above.
Past joint injury
Another well-established cause of osteoarthritis is post-traumatic, with about12% of cases due to underlying joint injury. It is an important area of active research as most patients in this category are young.
Athletes commonly get sprains and injuries to their joints. Other forms of roadside accidents, slipping and falling on a joint, weight lifting etc. are other forms of injuries. Quite understandably, after an injury, it may be difficult to use that joint and the patient is often advised to rest the joint. There might also be swelling of the joint after the injury. These are similar situations that set the ground for osteoarthritis. Investigations (3) conducted on the blood and the joint fluid from the affected joint show that there is a surge in the inflammatory cytokines. This leads to increased fluid build-up in the joint space. Cartilage thinning and degradation can be marked.
The joint injuries are usually tended by the physicians with painkillers etc. the progression of osteoarthritis is not sudden. However, later in months to years, the cartilage and bone can go downhill and deteriorate to post-traumatic osteoarthritis.
Other risk factors
The causes and risk factors of osteoarthritis make a long list. Some other risk factors are explained below:
Occupation
Studies have shown that occupations requiring increased and strenuous joint activity cause increased chances of getting osteoarthritis in those joints. Factory workers that overuse the prince’s grip, get OA in the phalanges. People who are laborers or have jobs requiring increased weightlifting, squatting or bending get OA in their knees and hip joints.
Diet
Bone and cartilage health is inversely proportional to disease risk. A diet lacking adequate amounts of vitamin D and calcium can lead to weak bones, predisposing diseases like osteoarthritis particularly in old age. Similarly, low calcium intake can severely compromise cartilage healing. Vitamin C is also seen to be linked with good bone outcome and hence decreased chances of getting osteoarthritis.
Surgery
As discussed earlier, injuries to joints are not a rare sight. Surgeries to correct alignment of the bones at the joint, to replace the meniscus etc. can similarly cause tears of bone, tendons and cartilage. Combined with other risk factors, this can give rise to osteoarthritis.