Despite the frequency of torn ACLs, many people don't know that the injury results in a significant risk of developing arthritis within 10 to . Around 70 to 80 percent of patients with a torn ACL will develop arthritis within that timeframe. Because most ACL injuries occur in young people, this means that arthritis could set in at a very early age. If a patient is 15 years old when she tears her ACL, for example, she could be struggling with arthritis by the age of 30.
Source: Medical Xpress