Genetic information can be valuable for amateur athletes, too—regardless of skill level, someone about to join a recreational basketball league or a tennis club would be well-served to know if they’re at risk of blowing out an ACL or tearing an Achilles. Each year, around 2 million adults go to the emergency room for sports-related injuries, many of them acquired during pickup games or matches in recreational leagues.

Within the field of sports-injury genetics, some studies have focused on variations in the genes that control the production of collagen, the main component of tendons and ligaments. Collagen proteins also form the backbone of tissues and bones, but in some people, structural differences in these proteins may leave the body’s structures weaker or unable to repair themselves properly after injury. In a study published in the British Journal of Sports Medicine in 2009, South African researchers found that specific variations of a collagen gene named COL1A1 were under-represented in a group of recreational athletes who had suffered traumatic ACL injuries. Those who had torn their ACL were four times as likely as the uninjured study subjects to have a blood relative who had suffered the same injury, suggesting that genetics are at least partially responsible for the strength of the ligament.

The same COL1A1 gene has also been linked to other soft-tissue injuries, like Achilles-tendon ruptures and shoulder dislocations. In a review article that combined the results of multiple studies on the COL1A1 gene, published in the British Journal of Sports Medicine in 2010, researchers concluded that those with the TT genotype—one of three potential variants of the gene, found only in 5 percent of the population—are extremely unlikely to suffer a traumatic ligament or tendon injury.

However, because of the vast complexity of the human genome, it’s highly improbable that a single variant within a gene can determine a person’s genetic risk for a given soft-tissue injury. Researchers agree it’s much more likely that these injuries, like complex conditions such as obesity or type 2 diabetes, are influenced by multiple genes.

The COL5A1 gene, another one associated with collagen production, has been linked to a higher risk of injury of the ACL and Achilles tendon, as well as greater susceptibility to exercise-induced muscle cramping. A 2013 study in the Clinical Journal of Sports Medicine found that specific variants of COL5A1 were strongly correlated with muscle cramping among runners in the Two Oceans Marathon in South Africa.

Researchers have also identified genetic markers associated with bone-mineral density, an important measure of bone strength that provides clinicians with information on a patient’s risk of fracture. One gene combination, investigated in a 2010 study in the journal BMC Genetics, was associated with a nearly four-fold increased risk of stress fractures among army recruits. A separate study, published in the Archives of Pediatric Adolescent Medicine in 2009, found that osteoporosis in older women and increased rates of stress fractures in young women also tend to run in a family.