A Seoul orthopedic surgeon explains why an MRI
A Seoul orthopedic surgeon explains why an MRI often comes before any decision about knee surgery — and how faster scans and same-day reading change the visit

SEOUL, South Korea - For most people with knee pain, the first test is an X-ray. It is quick, widely available and good at showing how much space is left between the bones. But it leaves out much of what matters when deciding between treatments.

"An X-ray tells us how much space is left in the joint," said Yeong Seok Lee, M.D., Ph.D., an orthopedic surgeon at St. Luke's Hospital in Seoul. "An MRI tells us what is happening to the cartilage and meniscus inside it — and that is often what decides whether a joint-preserving option is worth discussing."

Here is how the two tests compare:

X-rayMRI
What it showsBones, the space between them, bone spurs and leg alignmentCartilage, meniscus, ligaments, fluid and changes inside the bone
Typically used forGrading arthritis; checking alignment while standingLocating cartilage damage; planning procedures
What it cannot show wellCartilage, meniscus and ligaments directlyHow the knee behaves under body weight
RadiationSmall doseNone (uses a magnetic field)
TimeA few minutesLonger; patient lies still inside the scanner

The two tests work together rather than replacing each other. A standing X-ray shows the stage of arthritis and how the leg is aligned. An MRI shows where cartilage is damaged and how large the area is — details that matter for treatments such as arthroscopic repair, bone marrow injection or CARTISTEM®.

Not every painful knee needs an MRI. It is most useful when symptoms do not match the X-ray, when the knee locks or gives way, or when a procedure is being considered.

At St. Luke's Hospital, MRI scans are taken on site and read by a full-time radiologist, so patients can have the scan, the reading and a consultation with their surgeon on the same day. The hospital also uses SwiftMR®, an AI-based MRI software that is FDA 510(k)-cleared and, according to the manufacturer, can shorten scan time by up to 50%.

"A shorter scan matters, especially for people in pain who find it hard to lie still," Dr. Lee said. "But the bigger difference is that a radiologist reads it here, the same day, so we can go through the images together before anyone talks about treatment."

A full-time anesthesiologist is also on staff. If the imaging points toward a procedure, the surgery and anesthesia can be planned within the same hospital, by the same team that reviewed the scan.

People with pacemakers, some metal implants or other medical devices should tell the team before an MRI, as these may affect whether a scan can be done safely.

Patients in the United States who already have a knee MRI can send the imaging files and radiology report for a review from home through international.slmc.co.kr/medical-review. The team replies in English within three business days, and consultations are held directly in English with Dr. Lee.

Regulatory note: CARTISTEM® is approved for specific uses in South Korea. It is not FDA-approved for commercial use in the United States. Treatment suitability, expected benefits, limitations, risks, and alternatives should be reviewed individually.

Next in the series (October 27): Bone marrow injection for knee arthritis — what it is and what it isn't.

About Yeong Seok Lee, M.D., Ph.D. Dr. Lee is an orthopedic surgeon focused on knee and shoulder care and a Clinical Professor at Sungkyunkwan University School of Medicine (Samsung Medical Center). His research has appeared in The American Journal of Sports Medicine and the Journal of Shoulder and Elbow Surgery.

About St. Luke's Hospital. St. Luke's Hospital is a multi-specialty hospital in Seoul, open 365 days a year, with full-time radiology and anesthesiology specialists on staff, and about an hour from Incheon International Airport. Its Stem Cell & Joint Preservation Center offers knee care ranging from injections to cartilage procedures and joint replacement. international.slmc.co.kr

Media contact: International Team, St. Luke's Hospital · [email protected]

This release is for general information and is not medical advice. Individual results vary.