The most likely cause of this patient's left knee osteoarthritis is meniscectomy. The history of prior injury followed by meniscectomy puts this patient at substantial risk for the development of osteoarthritis at an earlier age than would otherwise be predicted. A recent prospective study with a 40-year follow-up concluded that meniscectomy leads to osteoarthritis of the knee with a resultant 132-fold increase in the rate of total knee replacement in comparison to their matched controls. The risk of osteoarthritis of the knee following meniscus injury and removal is also well documented for adolescent athletes and, as recognition of this link has become more widespread, the incidence of meniscus repair rather than meniscectomy has risen.

Other factors for osteoarthritis are advancing age, obesity, female gender, and genetic factors. For example, obesity is the most important modifiable risk factor for osteoarthritis of the knee, but this patient is not obese. The incidence of knee osteoarthritis is also increased by occupations with repetitive bending, which this patient does not experience. The prevalence of osteoarthritis of the hip and knee is nearly two times higher in women than in men. Osteoarthritis of the hand has strong female and genetic predilections; it is also associated with obesity. His mother's hand osteoarthritis is probably not relevant for this patient who developed knee osteoarthritis at an early age following meniscectomy.