In one word: “demographics.”
  Here are five reasons from Shirley A. Engelhardt, President and Founder of ORTHOWORLD Inc., a strategic services firm solely focused in orthopaedics, and Founder and Managing Member of Knowledge Ventures, LLC, an early stage musculoskeletal investment fund.
5 Reasons:
1) We’re getting older. 
2) We’re becoming more demanding, both mentally and physically.
3) We’re not taking such good care of our bodies, even at a young age.
4) We’re continuing to believe, at 40 or 50, that we’re still 25.
5) We’re prone to falls, accidents and other foibles of daily living (and always will be).
Shirley Englehardt has plenty of facts and data to back that up, and if you are in (or thinking about entering) the medical orthopedic parts market, the article  at the link below will be Gold for you.
Orthoworld article.
Photocredit:
Thanks to Jeff Remaley at Orthoworld for sharing the great article.