Disuse osteoporosis occurs due to lack of weight-bearing activity. Which option best describes this condition?

• A. Weight-bearing activity
• B. Regular exercise
• C. Adequate calcium intake
• D. Lack of weight-bearing activity

Answer: (D)

Disuse osteoporosis comes from a lack of mechanical stress on the bones. Bones strengthen in response to loads; weight-bearing activities such as standing, walking, and resistance exercises create the strains that stimulate bone formation. When those activities are reduced or absent, osteoclast activity can outpace osteoblast activity, leading to a loss of bone density and thinning of the trabecular structure. Therefore, the condition is best described by a lack of weight-bearing activity, since the absence of mechanical loading is what drives the bone loss.

Regular exercise and adequate calcium intake support bone health, but they describe protective factors rather than the cause. The lack of weight-bearing activity directly explains why bone density decreases in disuse osteoporosis.