Just How Common are ACL Injuries, and Where Does Replacement Tissue Come From?

23 September 2015

An Anterior Cruciate Ligament (ACL) sprain or tear is one of the most common orthopedic injuries, especially among athletes. It happens when the top of the leg, or the femur, spins one way, and the bottom half spins the other, or when there is a direct impact to the knee. More than 300,000 of these injuries will happen in any given year in the US alone, and double that worldwide. That’s one in 1,750 people between the ages of 15 and 45, the most actively athletic cohort in the population.

70% of ACL injuries will be sustained in one of the following sports: basketball, soccer, skiing and football. Women who play sports are more likely to have this kind of injury (NCAA indicates that studies range from twice as likely to eight times as likely).  UCSF researchers say that this is due to a combination of factors, including “wider pelvis, knee valgus, foot pronation, joint laxity, hamstring flexibility, muscle development, hormonal differences, and ACL size.”

A third of these will injuries will be bad enough to require surgery within the year.

Surgical intervention on an ACL injury requires replacement ligament tissue. Tissues have traditionally been obtained from one of three sources:

  • a human cadaver, which is unpredictably available, and requires a person with young healthy ligaments to die 
  • from a person’s own body, which requires a second surgical site to harvest tissue from somewhere else in the person’s system (where it’s likely also needed) (autograft)
  • from a synthetic tissue, which is weaker, less durable and has lower performance than organic tissues


Early attempts to use animal tissues failed due to rejection by the patient. That is, until the development of Aperion Biologics Z-process, which isolates and removes the offending antigens – and makes the tissue not only safe for transplantation, but helps it grow and remodel itself into the patient’s own tissue overtime.   Animal derived tissue has been approved for surgeries in Europe, and has been in trials in the United States.

These advances in tissue availability from animals mean that the one third of ACL injured patients who have to have surgery can have confidence that there will be quality tissue available when they need it and they won’t have to have tissue harvested from other parts of their body. For tens of thousands of people each year, getting back to an active lifestyle is closer than they might have thought.

The field of tissue engineering and regenerative medicine will continue to offer medicine a ready supply of organic replacement parts for the human body. The ACL is only the beginning.

Sources: American Academy of Orthopedic Surgeons, NCAA, UCSF Orthopedic Clinic, National Institutes of Health