2.6. CHAPTER CONCEPTS 29
• The costs of cartilage injuries can be signiﬁcant to both the young and the elderly. Traumatic
injuries are seen with automobile accidents and, recently, with combat trauma.
• Osteoarthritis (OA) affects over one ﬁfth of the US population over 45 and almost one half
of those over 65.
• OA cartilage loses proteoglycans and possesses lower mechanical properties. Wear of the
cartilage can lead to complete destruction of the articular surface and signiﬁcant pain.
• In the US alone, costs of OA are in excess of $65 billion per year (both medical costs and lost
wages). Comorbidities are common with OA and are also costly to manage.
• In addition to the elderly, cartilage injuries in children and adolescents are increasingly ob-
served, with roughly 20% of knee injuries in adolescents requiring surgery.