What you should know about knee instability and dislocations in young athletes

lead image Milewski patellofemoral instability

Pain in the kneecap (patella) is very common in young athletes. It’s estimated that up to 15% of adolescents get some degree of patellofemoral pain. Most can be treated with rest, ice, non-steroidal anti-inflammatory drugs (NSAIDs) and sometimes rehab exercises. But instability of the patella — known as patellofemoral instability — is relatively less common, and more worrisome for children and adolescents.

The term “patellofemoral instability” can refer to either a traumatic injury in which a person dislocates their patella, or just general instability in the knee that a person may feel or a physician may observe upon examination. In both cases, it’s important the individual receives the proper treatment in order to avoid long-term damage.

Thriving talked to Dr. Matthew Milewski, a pediatric orthopedic sports medicine surgeon in Boston Children’s Orthopedics and Sports Medicine Center, about what kids and parents should be aware of if they experience this knee condition.

Are there certain sports that put an athlete more at risk for this injury?

Patellar instability is incredibly common, some have reported it to be even more common than ACL injuries. We see it in a variety of different sports, and certainly in contact sports like football and lacrosse. But we also see it in jumping sports and sports that involve a significant amount of twisting, like basketball, volleyball, gymnastics and dance. It’s a little less common in sports that have more protection over the knee, like hockey.

What causes patellofemoral instability?

When someone dislocates their patella, it’s usually a traumatic event — they are hit or they take a really hard pivot, turn or awkward landing. If they twist or rotate around their leg, the kneecap can slide off to the side.

Sometimes a patient can suffer from patellar subluxation, which is just a small shift of the patella where it starts to dislocate but comes back into place. It’s not a full dislocation, but it can still be quite painful for the patient and can cause them to have what we call “apprehension,” where they’re anxious about their kneecap moving out of place again. There are a number of factors that can contribute to this.

What factors put an athlete more at risk for instability?

Both dislocation and subluxation can be a result of many different factors:

  • Gender: adolescent females are generally more flexible than their male counterparts, making them more prone to patellofemoral instability.
  • Family history: if a parent has experienced a dislocation, their kid is more likely to have recurrent instability.
  • Genu valgum: being “knock kneed” places an adolescent at greater risk for instability.
  • Patella alta: if a patient’s patella is slightly higher than normal, it may indicate that they’re more likely to experience instability or dislocation.
  • Trochlear dysplasia: the groove at the end of the femur (thigh bone) where the patella rides is shallower, meaning the patella isn’t fully captured within that groove.
  • Femoral anteversion: the individual’s hips are turned in a little more than normal, placing them at greater risk for knee problems.
  • External tibial torsion: the individual’s feet are turned out as a result of patellofemoral malalignment.

All of these factors are small components, but contribute to the bigger problem of the kneecap being more prone to dislocation.

How can patellofemoral instability be prevented?

One thing that can help is a patella stabilization brace – what we often call a lateral buttress. It has a C-shaped pad over the outside portion of the kneecap to help provide some external compression and keep the kneecap well-centered.

Another option is physical therapy, as strengthening the quad, hip and core can really help with stabilization of the lower extremities. It can also help individuals recover from patellofemoral pain syndrome, and to some degree control patellofemoral instability.

How is it treated?

If an athlete dislocates their knee during a sport or activity, a licensed medical professional may be able to get the kneecap back in place right away by straightening the patient’s leg, as often the kneecap will pop back in by itself. But if the patella needs to be pushed back into place, the patient should be taken to an emergency room or urgent care clinic.

Sometimes, patients will require sedation or some relaxation medication, particularly in an ER setting, to make it easier to get the kneecap back into place — and of course to also make the patient more comfortable. Most patellar dislocations should get x-rays to make sure there are no obvious fractures and that the patella is reduced properly.

As a pediatric orthopedic sports medicine surgeon, the patients I usually recommend be referred to me for surgical evaluation are those who have dislocated their patella and have a lot of swelling. If this is the case, it might be a more significant injury than just the dislocation, as a piece of bone or cartilage might have been knocked off.

I also recommend further evaluation for anyone who has had multiple dislocations, particularly in the younger population and athletes that want to get back to higher level competitive sports or activities. Sometimes conservative treatment can help, which includes bracing, physical therapy, and return to activities in a gradual process. But for patients that continue to have instability despite proper, conservative, non-operative treatment, we generally recommend surgery to help control the risk of further instability events.

Patellofemoral instability is a painful event, so reducing the risk of further instability is something that allows young athletes to get back to their sports and activities with more confidence and less anxiety.

Learn more about Boston Children’s Sports Medicine Division.