Osteoarthritis is indeed more common in older individuals, but it is not primarily due to genetic factors.

While genetics can play a role, the primary risk factor for osteoarthritis in older adults is wear and tear on the joints over time.

Choice B rationale:

Excessive weight is a well-established risk factor for osteoarthritis.

The rationale behind this is that carrying excess body weight puts additional stress on the joints, particularly the weight-bearing joints like the knees and hips.

This increased mechanical stress can lead to the degeneration of joint cartilage and the development of osteoarthritis.

Choice C rationale:

Osteoarthritis can be exacerbated by joint trauma, such as fractures, but it is not primarily caused by trauma.

The degeneration of joint cartilage and the development of osteoarthritis typically occur over time due to various factors, including mechanical stress and inflammation.

Choice D rationale:

While the exact cause of osteoarthritis is not fully understood, it is not accurate to say that it is entirely unknown.

Osteoarthritis is believed to result from a combination of factors, including genetics, aging, joint injury, and mechanical stress.

Understanding these risk factors can help in its prevention and management.