Ask a UCSF Benioff Children’s Hospital Expert

by Nirav K. Pandya, MD

“My Young Athlete Felt a Pop in Their Knee and Crumbled to the Ground” – What Could Be Going On?

With an increasing number of youth athletes engaged in year-round sports, there has been a drastic increase in the number of traumatic knee injuries. The immature knee cannot withstand the force from repetitive, high-level sporting activity. As a result, Monday morning phone calls to our office from patients who have suffered a painful knee injury from weekend sporting events are commonplace.

Many athletes describe hearing or feeling a “pop” in their knee before they fall to the ground. What could possibly be going on inside the knee?

A “pop” in the knee can vary from conditions that are dreaded (knee cap dislocation, torn ligament, meniscus tear, bones impacting one another) to those that are seemingly innocuous (a snapping tendon or sporting equipment hitting the ground). The two most important factors that determine the severity of the injury after a “pop” in the initial time frame are the ability of the athlete to return to play immediately after the injury, as well as the degree of swelling in the knee. For patients whose knee swells up after the injury, this indicates a more serious injury as blood may be entering the joint from trauma.

Immediately after the injury, medical personnel should examine the knee and determine the severity of the injury. The young athlete may be instructed to go to the emergency room or present to their doctor within a day or two. In the interim, it is important to elevate the leg, place ice on the affected area, limit walking, and take pain medication as needed.

Once your young athlete visits their doctor or pediatric orthopedist, a thorough history of what happened should be taken and a physical examination should be performed. Even though you might be concerned that the “pop” was a ligament tear, an x-ray will likely be taken to make sure your young athlete did not break a bone. Since an x-ray cannot visualize the cartilage and ligaments, many athletes will then obtain MRI to take a closer look more at these structures.

It is important to note that the vast majority of knee injuries with a “pop” are not emergencies. As you await the results of your young athlete’s MRI, they may be instructed to continue limiting activity and perhaps participate in basic physical therapy to regain range of motion and strength.

The most common diagnoses in adolescent athletes who present with the dreaded “pop” and fall to the ground are knee cap dislocations, anterior cruciate ligament injuries, and meniscus tears. The ability to return to play will be determined based on the degree of injury, the specific sport you play, and where in the season one currently is. Regardless, the treatment team will put together a plan that will get your young athlete back on the field in the safest, most efficient manner.

Just remember, when your young athlete or one of their teammates experiences the dreaded “pop” and falls to the ground, there could be multiple injuries that may have occurred. The ability to return to play and the degree of swelling after the injury aid in determining the severity of the injury. Help them to keep their spirits up and hope for the best if this occurs.


Nirav Pandya, MD, is a pediatric orthopaedic surgeon and the medical director of the Sports Medicine Center for Young Athletes at UCSF Benioff Children’s Hospitals.