By: Steve Siwy for Knee1A recent study has found that the genetic regulation of osteoarthritis in the knee may be linked to certain physical traits and conditions. While the study did not investigate genetically-based causes for osteoarthritis, it did find commonalities among people whose parents had arthritis of the knee.
The study, appearing in the October issue of the Annals of the Rheumatic Diseases, was performed by researchers at the Menzies Center for Population Health Research in Tasmania, Australia. It compared a group of 188 people between the ages of 26 and 60 who had at least one parent who had undergone total knee replacement surgery for severe knee osteoarthritis (the “index” group) with another group (the “control” group) of 188 people, matched one-to-one with the first group by age and sex, with no family history of the condition.
The study found that people in the index group tended to have higher body mass indexes, weaker leg muscles, and higher incidence of knee pain than those in the control group. Subjects in the index group also tended to have a larger bone area in the medial tibial compartment (the inner part of the shinbone, closest to the knee joint). Among the traits tested that did not appear to be more statistically prevalent in the index group were height, endurance fitness, and the volume of cartilage in the knee.
Osteoarthritis occurs when the surface of the bone near the joint is damaged. The prefix “osteo-“ comes from Greek via Latin, and means “bone.” Arthritis is inflammation and damage of the joints. The term “osteoarthritis,” then, describes a type of joint inflammation different from, for example, rheumatoid arthritis, which is caused when the body’s own immune system attacks the joints.
When osteoarthritis develops in the knee, the cartilage, which normally cushions the joint and allows the bones to move smoothly against each other, roughens and wears away. The bone then grows thicker in compensation, as do the tendons and capsule, even as the leg muscles weaken. The result is pain, stiffness, and instability in the joint, with the possibility of the joint giving way when weight is put upon it.
Many factors increase a patient’s risk for osteoarthritis. It is more common in older people and women, as well as the overweight and obese. Having an injury to the knee also increases a person’s chance of developing osteoarthritis later in life. Researchers have yet to pinpoint specific genes that might be responsible for osteoarthritis, or that might serve as a marker that a patient is predisposed for the condition. However, studies have shown that genetics do play a role, demonstrating that those who have parents or siblings with knee osteoarthritis are at a higher risk of developing osteoarthritis themselves.
This study, showing that children of people with osteoarthritis have traits in common, and at a rate higher than that of the general population, further buttresses the case for a genetic link to knee osteoarthritis, as well as shedding light on some of the mechanisms by which a genetic tendency toward the disease can express itself.
