Soccer players are bow-legged at remarkably high rates, with studies finding that 55% to 81% of professional players have some degree of outward knee bowing. Compared to non-athletes, where the rate sits around 2%, that gap is enormous. The short answer: years of intensive training during childhood and adolescence physically reshape the growing bones around the knee, pushing them into a bowed alignment that persists into adulthood.
How Soccer Reshapes Growing Bones
The medical term for bow legs is genu varum, and in soccer players it develops through a specific mechanism. During childhood and adolescence, bones grow from soft areas called growth plates near each end of the bone. These plates are responsive to mechanical stress. The repetitive kicking, cutting, and sprinting in soccer place asymmetrical forces on the growth plates around the knee, favoring outward bowing over time. Think of it like a young tree growing crooked because wind constantly pushes it from one side.
Some researchers point to the adductor muscles (the inner thigh muscles that soccer players use heavily for passing, shooting, and lateral movement) as a key driver. These muscles generate strong inward-pulling forces on the upper leg that could influence how the bones develop. However, this explanation has limits: the adductors don’t actually cross the knee joint, and studies show no difference in bowing between a player’s dominant kicking leg and their standing leg. That suggests the issue is more about overall loading patterns during play than any single muscle group.
The Critical Age Window
Not all years of soccer training contribute equally. The bowing effect is most pronounced during the teenage growth spurt, particularly between ages 13 and 18. Research on adolescent players found that the highest degree of bowing appeared in the 16 to 18 age group. This makes sense biologically: age 16 marks roughly the end of the major growth spurt in boys, and the final two years of skeletal growth appear to be when male athletes naturally trend toward a slightly bowed alignment. Intensive soccer training during this window amplifies that trend significantly.
One study comparing adolescent soccer players to non-athletic peers of the same age found genu varum in about 37% of the soccer group versus just 2% of controls. The stress and repetitive loading on the knee joint during this growth period creates more severe bowing that then becomes permanent once the bones finish growing and the growth plates close.
Does Bowing Help or Hurt Performance?
There’s a common assumption that bow legs give soccer players some advantage, perhaps better stability or quicker direction changes. The evidence doesn’t really support this. Bowed alignment is actually associated with reduced dynamic balance, meaning balance while moving. That said, most players with bowed legs perform at a high level without noticeable limitations, and the condition typically isn’t painful during their playing years.
The real concern is long-term joint health. Bow legs shift the weight-bearing line of the leg so that more force passes through the inner compartment of the knee. Over years and decades, this accelerates cartilage wear on that side. Studies of former professional soccer players show high rates of knee osteoarthritis, and the bowed alignment is a significant contributing factor. Players also face greater risk of anterior cruciate ligament (ACL) injuries and anterior knee pain, both linked to the altered mechanics that bowing creates.
Selection Bias vs. Training Effect
One question researchers continue to explore is whether soccer causes bow legs, or whether kids who already have slightly bowed legs are drawn to soccer (or are better at it early on, earning more playing time and coaching attention). The answer is likely both. Some degree of natural variation in leg alignment exists in all children, and a child with a slight natural bow may find the stance and movements of soccer more comfortable. But the dramatic difference in prevalence between soccer players and both non-athletes and athletes in other sports like handball, basketball, and volleyball points strongly to the sport itself as a major factor. The training effect on growing bones is real and well-documented.
Can Bow Legs Be Corrected?
Once the bones have finished growing, bow legs from soccer training are a structural change. No amount of exercise, stretching, physical therapy, or supplements will alter bone shape. Strengthening the muscles around the knee can improve joint stability and reduce injury risk, which is valuable on its own, but the bowing itself is permanent without surgery.
For players or former players whose bowing causes pain, accelerated joint wear, or functional problems, surgical correction is an option. The procedure involves cutting the bone and realigning it, a process called osteotomy. For mild to moderate bowing (under 12 degrees) occurring in the shinbone, surgeons typically use a plate and screws. Larger deformities or those involving the thighbone require different approaches. Recovery is significant, and these procedures are reserved for cases where the misalignment is causing real problems, not for cosmetic concerns alone.
Protecting Young Players
Prevention programs like the FIFA 11+ warmup, widely used in youth soccer worldwide, focus on strengthening the muscles around the knee, improving landing mechanics, and building single-leg stability through exercises like planks, Nordic hamstring curls, single-leg squats, and controlled jumping drills. These programs meaningfully reduce injury rates. However, they haven’t been shown to prevent the gradual bone remodeling that causes bowing, since the issue is fundamentally about repetitive mechanical loading on growing bones rather than muscle weakness or poor movement patterns.
For parents of young soccer players, the practical reality is that moderate training volumes during childhood carry less risk than intensive, year-round play during the growth spurt years. Diversifying sports during adolescence, rather than specializing exclusively in soccer, reduces the repetitive loading pattern that drives bowing. Once a player reaches skeletal maturity in their late teens, the growth plates close and the alignment is essentially set for life.