When Yoo Ji-na, a novice runner, visited a local orthopedic clinic for knee pain after completing her first 10-kilometer race, she couldn’t shake the odd feeling of being warmly welcomed by the clinic’s doctor and staff.

Even before she had a chance to explain in detail how the pain started and developed, the doctor was already pinpointing the likely cause: "A lack of muscle strength in your thighs and glutes, especially the gluteus medius."

He was seeing a growing number of patients like her, ever since running became a trend, he added, promptly searching Google for videos to recommend specific exercises, such as clamshells and lunges.

"It's a bit of a secret," a therapist later said in a hushed tone, "but my doctor has made quite a profit from runners."

Yoo paid a total of 150,000 won ($106) in medical bills, which included extracorporeal shock wave therapy, physical therapy, and an ultrasound examination. While this may seem affordable from some perspectives, in South Korea, a typical local clinic visit rarely exceeds 10,000 won, thanks to the extensive coverage provided by public health insurance. She was told to return a week later.

The therapist further revealed many people visit the clinic with knee, ankle or foot injuries after taking up running.

According to a Gallup Korea survey, running saw the biggest increase in popularity, with 32 percent of respondents reporting to have run at least once in 2023, up from 23 percent in 2021. It was the highest growth among all sports.

The exposive popularity of running is also reflected in the record-breaking participation in various run events, including marathons. The Seoul Half Marathon, hosted by the Seoul Metropolitan Government in April, attracted 13,000 participants, up from 7,000 last year. The Seoul Marathon, hosted by the media firm JTBC in November, drew 35,000 participants.

Despite its accessibility, running comes with risks. Many, like Yoo, start casually but end up with injuries due to inadequate preparation. One common issue is iliotibial band syndrome, caused by the irritation of the iliotibial band – a thick tissue along the outer thigh – rubbing against the knee.

According to the Health Insurance Review and Assessment Service, the number of patients treated for iliotibial band syndrome rose from 5,935 in 2010 to 16,605 in 2023, with a notable surge in recent years – 12,204 in 2020, 13,244 in 2021 and 14,931 in 2022.

Experts say the running injuries often result from insufficient warm-ups, lack of regular exercise, weak gluteal and hamstring muscles and improper technique.

Kim Byung-gon, a medical doctor who formerly served as health director for Gabonese president, said on a YouTube channel run by Channel A News when he visits the Han River, he sees only 10 percent of runners using proper form — the other 90 percent are at risk of injuring their ankles, knees or lower back. He added muscles and flexibility should be supported for better running.

“Running is easily accessible to anyone, but without mastering basic posture and developing foundational muscles, beginners are prone to injuries,” said Park Seo-yoon, a former Adidas running coach, emphasized the importance of learning proper running techniques. “For those just starting out, focus on gradually increasing your distance before jumping into races. Always warm up before running and cool down afterward to prevent injuries.”