Choice A rationale:

Obesity is a primary risk factor associated with the development of osteoarthritis.

Excess body weight places increased mechanical stress on weight-bearing joints, such as the knees and hips, which can lead to the degeneration of joint cartilage and the development of osteoarthritis.

Choice B rationale:

Genetic factors can contribute to the risk of developing osteoarthritis, but they are not the primary risk factor.

Obesity and joint injury are more commonly recognized as primary risk factors.

Choice C rationale:

Advanced age is a risk factor for osteoarthritis, particularly in older individuals.

However, it is not the primary risk factor.

Obesity and joint injury play more significant roles in the development of the condition.

Choice D rationale:

Joint injury, such as fractures or repetitive trauma, can contribute to the development of osteoarthritis, but it is not the primary risk factor.

Obesity is a more significant primary risk factor.