The knee is the second most common site of injury that occurs in all high school athletes, and the most common site of injury to high school football players.

Research has shown that 20 percent of all high school football injuries occur at or around the knee. The most common types of knee injuries in high school football are: incomplete ligament tears, complete ligament tears, torn cartilage, fracture/dislocations, tendon tears, and contusions.

Up to 40 percent of knee injuries in high school football may require surgery at some point. From a medical and a purely athletic standpoint, knees are clearly the most valuable body part of the high school football player.

Let’s take a look at the key internal parts of the knee most vulnerable to football injury (see diagram):

Ligaments: There are four main ligaments of the knee: two on the sides of the joint (medial (inner) and lateral (outer) collateral ligaments) and two on the inside of the joint (anterior (front) and posterior (rear) cruciate ligaments).

Cartilage: There are two half-moon shaped cartilage (medial and lateral meniscus) on the inside of the joint and a thin layer of cartilage that covers the bones on the inside of the knee joint (articular cartilage).

The most common football injury to the knee is to the medial collateral ligament (MCL). This ligament is on the medial side of the knee joint and is usually injured in one of two ways: a non-contact twisting injury, when a football player is attempting to plant and cut; or when the player is a tackled or blocked from the outside of the knee joint. The majority of these injuries can be treated with healing rest, bracing, and physical therapy.

The second most common football injury to the knee is to the anterior cruciate ligament (ACL) on the inside of the knee joint. This ligament runs from the anterior (front) medial (inside) joint up and back (posterior) to the lateral (outside) part of the internal knee joint. This ligament is most commonly injured with a non-contact twisting injury, like when a football player is attempting to plant and cut; it may also be injured in a twisting injury while being tackled or blocked. This injury, if isolated and only a partial tear, can be treated with healing rest, bracing, and physical therapy. However, if the injury is more severe, arthroscopic knee ligament reconstruction surgery is the gold standard treatment of choice to allow the athlete the best chance to return to full function. Rehabilitation will take up to nine months.

The semi-mobile, half-moon shaped cartilage called menisci, reside on the inside of the knee joint (see diagram). The most common injury in football is to the medial meniscus, due to a twisting injury (non-contact or contact). If a small tear, the high school athlete may be treated with healing rest, bracing, and physical therapy. If the tear is large enough and causing significant restriction of football function, arthroscopic surgery to debride (clean out) the tear is advised. Meniscal repair can be another option of surgical treatment, but the rehabilitation will take more than six months.

Injury to the articular cartilage (see diagram), the smooth cartilage surface that covers the bones on the inside of the knee joint, is a serious problem to the high school athlete. This thin cartilage provides the friction-free smooth gliding surface that allows joints to move normally. Traumatic injuries in high school football can damage or shear off an area of this cartilage, such as with a violent twisting injury while being tackled or blocked.

When these injuries cause pain, swelling and catching in the knee, treatment may be indicated. When torn or damaged cartilage is left untreated, it can progress to arthritis. This is a rapidly-growing area of orthopedic surgery now that surgeons are able to re-grow or transplant cartilage back into the knee to delay or prevent the progression to arthritis. Rehab can take up to 9-12 months depending on the size and depth of the injury. An articular cartilage knee injury should be suspected if chronic swelling becomes a problem for any knee injury, and sometimes an MRI can pick up swelling just below the surface of this cartilage and it then may be called a “bone bruise."

The remainder of serious knee injury types in high school football include patellar tendon ruptures (which will require surgery and rehab for nine months or more); and patellar (kneecap) dislocation, which will require at least six weeks of healing rest, bracing, and a focused physical therapy regimen to prevent recurrence.

Sadly, research studies have identified illegal sports activity (penalties such as clipping or other blocks below the waist) as risk factors for major knee injuries in high school football. Although illegal play was identified as a contributing factor in only 5 percent of all knee injuries, 20 percent of the knee injuries resulting from illegal play required surgery. This finding suggests the importance of making it clear to athletes, parents, coaches, and officials that illegal play has the potential to cause serious injury.

The best advice to area high school football athletes: do not hesitate to see your school athletic trainer if you suffer even what you consider a minor knee injury. Early identification of your injury and proper treatment will prevent your minor injury from putting you at risk for a potentially season-ending injury.

Although preventive knee bracing has shown some promise in decreasing the frequency of serious knee injury to interior lineman, there is no evidence that it will prevent knee injury in skill positions. Functional strengthening during the season and, especially, in the offseason is not only good medicine to help prevent knee injury but has been shown to increase football athletic skill on the field.

(About the Author: John Tomberlin has worked with high school athletes in the Cedar Rapids Metro area since 1995. He was a four-sport athlete in high school and a high school coach for two years in Illinois. John has more than 25 years of experience working with athletes as a physical therapist and a certified strength and conditioning specialist. He has worked with professional athletes in the NFL, MLB, and on the PGA and LPGA tours. John also has worked with elite amateur athletes in alpine skiing, figure skating, and track and field.)