Knee Hyperextension Injuries

By: Steve Wowzynski, MPT, CMTPT/DN

If you follow NBA Basketball and our current NBA Champion Milwaukee Bucks, you’ve already witnessed players lying in the paint injured due to knee hyperextension. With big name players such as Giannis Antetokounmpo and Khris Middleton both losing playing time in the past year, knee hyperextension injuries can sound commonplace.  But are they?  

A knee hyperextension injury occurs when the knee is bent backwards to a greater extent than the natural restraint of the joint allows.  In physical therapy, when we measure extension at the knee, the normal amount of motion available at end range of a “straight” knee is between 0-5 degrees of bonus extension.  Some females with extra laxity may naturally extend even farther, between 5-10 degrees.  Either way, upon testing, there is a rigid end feel to the knee extension motion in a healthy, uninjured knee joint.   A hyperextension injury occurs when the knee is forced backwards farther than the athlete’s normal available joint play. 

On TV or in person, this injury appears very painful, because it is. The most common knee hyperextension injuries are due to over-stretching or spraining a ligament or straining a muscle or tendon due to excessive stretch. Injuries to any of these tissues cause swelling and pain that limits a player from participating in the rest of the game. More severe knee hyperextension injuries typically involve tears of the knee ligaments, most commonly the centrally positioned anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL). While partial ACL tears are possible, with the incidence between 10-25% of all ACL injuries, this is a relatively infrequent occurrence.  Treatment for these tears depends upon the stability of the injured knee during testing and functional activities.  In the most severe cases, an added compression mechanism of injury first damages the cartilage on the ends of the bones within the knee joint, referred to as articular cartilage.  More commonly, the thicker pad of cartilage that provides cushioning within the knee joint called the meniscus is injured along with the ACL. Compressive forces can also lead to fractures of bone, most commonly the tibia.  This is referred to as a tibial plateau fracture. Fractures and significant ligament sprains and cartilage injuries take additional time to heal, and many require surgery or at least immobilization with prolonged rehabilitation before returning to play.

Following assessment of the injury and imaging studies, if surgery can be avoided, any significant knee hyperextension injuries require the athlete to participate in a rehabilitation program. Early rehab goals include decreasing swelling utilizing ice and compression or other modality treatments, taping, specific activities, or hands-on therapy techniques. At the same time, the athlete will work to reestablish muscle activation around the knee. Weakness in the quadricep and hamstring muscle groups commonly occurs and must be improved before return to play. When the knee is stable, the athlete will be directed in activities to improve balance and functional strength during running, jumping, multi-directional movements and finally sport specific activities to prepare for the return to practice and in game action. If the knee hyperextension has caused damage that requires surgery, the athlete will still begin a rehab program following a specific post-surgical timeline to ensure the health of the knee as recovery is promoted. Surgery no doubt extends the time on the injured list, typically ending the season. The sports medicine team works together to set the specific timeline tailored to the needs of each athlete to safely and efficiently return to the court.