Performance-enhancing steroids are the gifts that keep on giving. They help set home-run records and win cycling medals — never mind make for obvious nicknames like the latest instant classic, A-Roid.

But those perennial gifts aren’t all "positive": Now, it seems, in addition to bulking up users, anabolic steroids also predispose them to musculoskeletal injuries.

An anonymous survey of 2,552 retired NFL players released today found an association between joint and ligament injuries and use of steroids. Just over 9 percent of the former pro-athletes, who played as far back as the 1940s and as recently as the 21st century, admitted using the drugs during their careers, the American Journal of Physical Medicine & Rehabilitation study showed. Doping was common among players in positions requiring size and strength, with 16 percent of offensive linemen and nearly 15 percent of defensive linemen fessing up to the practice.

Players who took the drugs suffered more disc herniations and injuries to their knees, elbows, necks, spines, feet, toes and ankles than those who didn’t use 'roids. For example, 21 percent of those who used the drugs said they'd suffered herniated discs, compared to 10 percent of players who didn’t take them. Nearly 31 percent of users hurt their elbows, versus 17 percent of non-steroid users.

That damage may stem from their cartilage adapting slowly (or not enough) to the increased muscle growth and force generated by the drugs, or from the greater mass and stress exerted on their ligaments and cartilage, according to the study. (Concussions have been shown to have lasting effects on football players, and players also have high rates of arthritis, but those conditions weren't studied in relation to steroid use.) "Our findings speak to the 'snowball effect' or compounded medical problems that appear to accompany steroid use," co-author Kevin Guskiewicz of the University of North Carolina's department of exercise and sport science, told the Associated Press.

Steroids do, however, seem to keep up muscle fiber density and cell nuclei (which boost the synthesis of proteins important to muscle development) even after people stop using them, researchers reported at last year's American Physiological Society meeting.

We're eager to hear if there are any “side effects” from the latest athletic supplement, Viagra. In the meantime, you can learn more about the science of football, why players dope, and whether juicing makes you a better athlete.

Image © iStockphoto/Stefan Klein