[chassis]

Hip as suspension ball joint analogy: look at the plastic bearing on the left.

The ball is the femur and has a static strength (breaking limit) and a fatigue life. weight + cycles = total fatigue load.

The plastic bearing is analogous to cartilage, ligaments and bursae. Genetics can be compared to whether a person has low grade carbon steel or high strength alloy steel for the ball. Relatively unknowable.

The analogy is challenged by the fact that the human body has some degree of healing. The unanswerable question is whether an individual is in front of, or behind, the healing curve.

More weight lifting, at heavier weight = shorter lifespan of any weight-carrying joint in the body, all else being equal. The hip joint is used illustratively.