Things That Go “Pop” in the Knee

Mark A. Pollard, MD
Assistant Professor of Orthopaedic Surgery
Orthopaedic Surgery and Sports Medicine
Cooper Bone and Joint Institute

One of the most frightening and disheartening things an athlete can experience is a “pop” in their knee as it gives out during an athletic event. A tear of the anterior cruciate ligament can be a devastating injury that can lead to long-term problems. These injuries often require surgical treatment.

The anterior cruciate ligament, or ACL, is one of the major stabilizing ligaments in the knee. It prevents the tibia, or shin bone, from sliding or shifting in relation to the femur, or thigh bone. The ACL is particularly vulnerable to injury during activities that involve rapid change in speed and direction, such as soccer, basketball, football, lacrosse and field hockey. Females tend to injure their ACLs at a higher rate than their male counterparts. Reasons for this gender discrepancy have been thought to be differences in muscle control, coordination, hormones and knee anatomical differences.

The goal of preventing ACL injuries has proven elusive. Bracing of the knee as a means to prevent injury has not shown benefit. Training programs have been developed to try to “re-teach” young athletes how to jump and land. These programs are currently being evaluated for effectiveness. Studies are also being conducted to test the effectiveness of injectable growth and healing factors to allow direct healing of the patient’s torn ACL. Most of these techniques are still in the experimental stage.

In the meantime, the medical standard for treatment of ACL tears is surgical reconstruction of the torn ligament. The ACL is normally in the center of the knee joint and is, therefore, bathed in joint fluid. This joint fluid prevents the patient’s own torn ACL from healing itself normally. Furthermore, the ACL typically tears in a manner that leaves torn ends resembling a mop that are not amenable to being simply stitched back together.

Reconstruction surgery involves replacing the patient’s original torn ACL with tissue from the patient themselves, called an autograft, or from donated tissue, called an allograft. The surgery can usually be performed arthroscopically, a minimally invasive procedure using small cameras through small incisions. Return to full sports can vary from six to 12 months.

No matter what the injury, advances in technique and rehabilitation have allowed even the most elite of athletes to return to their sport of passion. Seeking the right medical treatment quickly can help ensure proper diagnosis and healing process.

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