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In Street Clothes

Covering sports injuries from the perspective of a certified athletic trainer and backed by analytics.

Understanding Ben Simmons’ Patella Subluxation

The Philadelphia 76ers announced Thursday that guard Ben Simmons suffered a patella subluxation in the team’s recent win over the Wizards. The injury is the latest setback in what has been an up-and-down season for the Sixers and it has the potential to significantly impact their postseason aspirations.

While Simmons’ injury is serious it could have been much worse. The All-Star suffered a subluxation of the patella (kneecap) and not a knee dislocation. In a knee dislocation, the bones of the lower leg, including the tibia, are displaced from their normal alignment with the upper leg bone, the femur. This usually requires a violent force and is often accompanied by serious ligament damage. Furthermore, these types of injuries can be accompanied by blood vessel damage, making it a potentially limb-threatening injury. Knee dislocations are relatively uncommon in professional sports but have occurred. NFL quarterback Teddy Bridgewater suffered the injury in 2016 with Shaun Livingston being the most well-known NBA example.

Fortunately, a patella subluxation is different than a knee dislocation. The kneecap is a mobile bone that floats within the tendon of the quadriceps muscle group. It sits in a groove known as the trochlear groove and is able to glide in this groove throughout knee motion. However, if enough stress is applied to the area it can become displaced from the groove, like a train jumping the tracks.

When this occurs, the injury is classified based on what happens next. If the patella quickly returns to alignment the injury is diagnosed as a subluxation. If the kneecap stays displaced for an extended period of time, it is classified as a dislocation and often requires medical care to return it to its normal positioning.

The biggest issue following these types of injuries usually depends on the amount of damage sustained by the stabilizing structures in the area. The patella is equipped with ligaments that help hold it in place, but a subluxation can result in tearing of these structures. Cartilage damage can also occur. Fortunately, an MRI on Simmons was reportedly clean, suggesting these structures remain intact.

Several NBA players have suffered patella subluxations and dislocations in recent seasons, including Allen Crabbe earlier this year. Crabbe was back in action in 11 days, missing three games, following his injury. Former big man Chris Wilcox missed just five games following his patellar subluxation during the 2008-09 season. The other notable examples, including Andrew Bynum and Sergey Karasev, missed substantially more time, but those cases involved serious secondary damage to bone, ligament, and cartilage. Treatments options, including surgery, also influence the recovery timeline.

The Sixers continue to evaluate their treatment options and their final decision will ultimately determine if we see Simmons again this season. However, based on previous examples and what we know about his specific injury, there is reason for optimism. He will spend the next few days managing any accompanying symptoms like pain or swelling. Fortunately, there have already been reports that these issues are minimal.

If he does avoid an intensive treatment or surgery, look for Philadelphia to handle his recovery conservatively for the remainder of the seeding games in hopes he can be ready to go for the postseason. Simmons may elect to wear a stabilizing brace if and when he does return.

UPDATE (8/8/20): Simmons will undergo a debridement procedure to remove a loose body in the knee. The team loose body is used to describe a piece of bone or cartilage that is floating within the space of the joint. Simmons’ loose body likely occurred when the patella subluxed.