An 8-year-old girl comes in with knee pain, swelling, and a knee that catches and locks. She is not an athlete, and her symptoms did not start on the soccer field. Instead, they began with a simple activity: bending down to tie her shoe.

For Jennah Mann, MD, FRCSC, MHCDS, Surgical Director of the Sports Medicine Program in the Jackie and Gene Autry Orthopedic Center at Children’s Hospital Los Angeles, that type of presentation immediately raises suspicion for a discoid meniscus tear.

A congenital condition, a discoid meniscus is abnormally thick and shaped like a disc instead of a crescent. Its collagen structure can also be highly disorganized.

“A normal meniscus shouldn’t tear from a normal activity in a child,” Dr. Mann says. “This is a normal force on an abnormal meniscus.”

Unlike typical meniscus injuries that commonly occur in adolescent athletes, discoid tears more typically present in children under 10. Symptoms often develop during routine daily activities rather than sports, and diagnosis can be challenging.

“Discoid meniscus tears are often misread on MRI, especially at centers that don’t see them often,” Dr. Mann says. “When very young pediatric patients have meniscus pathology on MRI, they’re almost always a discoid.”

Although many surgeons see only one or two discoid meniscus patients a year, CHLA is among the highest-volume centers in the country for this condition. That experience is critical because discoid tears are not simply oversized versions of routine meniscus tears.

“The biology of a discoid meniscus is different,” Dr. Mann explains. “Sometimes the collagen looks normal. Other times it’s highly abnormal—it just kind of fluffs. It’s very difficult to make that into a meniscus.”

Not all patients with discoid meniscus tears need surgery. When they do—typically in response to symptoms that don’t resolve from physical therapy—surgeons need to carefully consider how much tissue to remove.

“If you don’t see a large number of these cases, it’s easy to end up over-resecting these tears, and then the child is left with no meniscus at all,” Dr. Mann says. “Conversely, if you don’t take enough tissue, it can be prone to re-tearing.”

The procedures can also be technically demanding. Patients are typically younger, requiring smaller instrumentation, and repairs often extend around much of the meniscus.

“These surgeries can take roughly twice as long as a routine meniscus procedure,” Dr. Mann notes. “It’s really important that patients are referred to high-volume centers from the beginning because preserving the right amount of tissue is critical to long-term knee health.”

One of the major challenges with treating these injuries is how much remains unknown.

“We don’t have data on how much tissue to preserve, or on how collagen quality affects long-term outcomes. There are a lot of unanswered questions,” Dr. Mann says.

To help build a more robust evidence base, CHLA participates in RAMPP (Research in Arthroscopy of Meniscus in Pediatric Populations), a multicenter prospective registry collecting outcomes data from children with meniscus injuries nationwide. CHLA has contributed 33 discoid patients to the registry—the third-highest total among participating centers and the most on the West Coast.

In addition, Dr. Mann is preparing to launch a prospective study examining the collagen composition of discoid menisci and how those characteristics influence tear patterns, healing, and long-term outcomes.

“Our long-term goal is to build a much better evidence base for this condition,” she says. “That will allow us to better predict outcomes, guide treatment, and give children the best chance at decades of knee health.”

(Newswise/HG)