Swiss researchers explained that deformities of the top of that bone - known as the femur - leads to reduced rotation and pain during movement among young competitive athletes.
This may explain why athletes are more likely to develop osteoarthritis than more sedentary individuals, according to Dr Klaus Siebenrock, from the University of Bern in Switzerland.
The researchers examined the physical condition and range of motion of 72 hips in 37 male professional basketball players and 76 hips in 38 control participants who had not participated in high-level sports.
Osteoarthritis and sports
The study showed that men and teens that had played in an elite basketball club since the age of eight were more likely to have osteoarthritis of the hip than in those who did not take part in regular sports. The athletes, the researchers found, had femur deformities causing their thighbone to have abnormal contact with their hip socket.
As a result, they had reduced internal hip rotation and painful hip movements. The study's authors noted these differences got worse during late adolescence.
Overall, the researchers found, athletes were 10 times more likely to have impaired hip function than those who did not play high-intensity sports.
The American Academy of Pediatrics provides more information on preventing teen sports injuries.
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Sport and osteoarthritis