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Complex Knee Injuries

  • A condition in which there is damage to two or more of the four knee ligaments
  • Symptoms include knee instability, movement difficulty, swelling, and intense pain
  • Treatment almost always involves surgery and physical therapy
  • Involves Orthopedics, Surgery

Complex Knee Injuries


Your knee is a freely moving hinge joint that allows you to bend and flex your leg as you walk, run and climb stairs, or twist, turn and pivot quickly. It takes a network of hardworking, interdependent ligaments to make those movements possible. If you fall or injure two or more of them at once, the treatment can be complicated. 

This type of injury is called a complex knee ligament condition, and it’s an important area of specialization for Yale Medicine Orthopedics & Rehabilitation, says Michael Medvecky, MD, chief of Yale Medicine Sports Medicine

What is a complex knee ligament condition?

The knee has four ligaments that work together in concert, says Dr. Medvecky. "You have the anterior cruciate ligament, the posterior cruciate ligament and then the two collateral ligaments,” he says. “When two or three or even all four get injured, the injury becomes exponentially more difficult to treat.”

What are the causes of complex knee ligament conditions?

There are several factors that make a knee ligament condition “complex,” says Dr. Medvecky. One factor is if  the case is a "revision” surgery, meaning that it is a corrective procedure designed to fix a previous knee procedure that didn’t go as planned.

“We are attempting to redo a surgery that didn’t work out the first time, and we have to identify and then correct what went wrong,” Dr. Medvecky says. “So we have to think about whether other ligament injuries were involved, or if the ligament graft was not placed in the most appropriate position or if there were other mechanical factors involved.”

More commonly, complex knee ligament conditions are caused by sports injuries in which two, three or all four of the ligaments in the knee tear at the same time. They may also be caused by a “high impact trauma,” such as a fall from a high place, a motor vehicle collision or an industrial accident. “These injuries have the potential to be devastating,” Dr. Medvecky says. “There can be nerve damage. Some of these injuries may even be limb-threatening, if the artery in the back of the knee is injured and not addressed immediately.”

What are the symptoms of a complex knee injury?

According to Dr. Medvecky, signs that more than one ligament may be damaged include knee instability, a history of a knee dislocation (not a kneecap dislocation), or difficulty with some types of movement, such as side-to-side motion, especially in association with swelling and intense pain. If you experience several of those problems at once, your knee injury may involve several ligaments.

How are complex knee ligament injuries diagnosed?

A medical history and clinical exam are the first steps to diagnosing a complex knee ligament injury. “We get a lot of information just by knowing how an injury happened,” says Dr. Medvecky. Motorcycle accidents and some types of sporting injuries often result in damage to several ligaments, he says. Imaging—including X-ray, magnetic resonance imaging (MRI) and sometimes computerized tomography scans—provide further detail to help identify which tissues and structures have been damaged.

How are complex ligament conditions treated?

Treatment for complex knee ligament conditions almost always involves surgery. “If we treat the injury acutely, within the first week or two after it has occurred, our recommendation is typically to repair the detached ligaments,” Dr. Medvecky says. “This can work because, most often, the tears don’t occur in the middle section of the ligament. They tend to pull or break off where they attach to the bone.” The surgical procedure involves reattaching the ligament to the native attachment point, he says. “Then we let nature heal it.”

A different approach is required for injuries that are not treated immediately or that only are correctly identified after they’ve become chronic. “Those typically require reconstruction, which means we are making a ligament rather than reattaching one,” Dr. Medvecky says.

The approach to these surgeries varies widely, depending on the nature of the surgery and the patient's overall medical condition. Some procedures may be done on an outpatient basis; others require a hospital stay of one or several days. Physical therapy is usually necessary. Patients who require ligament reconstruction may require a long rehabilitation period, possibly as long as 12 months, Dr. Medvecky says.

What makes Yale Medicine’s treatment of complex knee ligament conditions unique?

Because Yale New Haven Hospital is a Level I Trauma Center—a regional referral center for the comprehensive management of traumatically injured patients—orthopaedic surgeons treat an especially high number of  patients with complex knee ligament conditions. “These are injuries that other doctors aren’t seeing all that often,” says Dr. Medvecky. 

“We have developed a lot of knowledge and comfort with the anatomy of the knee that brings expertise in diagnosing and planning treatment that others may not be able to offer," he says. For the patient, that translates to a higher surgical success rate, particularly when treatment is highly complex.