Knee Ligament Injuries


Tears or ruptures of the knee ligaments usually are caused by trauma (e.g., sport-related injuries or falls, or a blow to the knee in a car accident). Ligament tears can cause pain and instability – a wobbling or buckling knee). Such conditions should be evaluated by a qualified physician, such as a sports-medicine specialist, orthopaedic surgeon, or physiatrist.

(A physiatrist is a physician specializing in physical medicine and rehabilitation, and focused on restoring function to people. Physiatrists treat a range of problems, from sore shoulders to spinal cord injuries. They see patients of all ages and treat problems that involve all the body’s major systems.)

Knee-ligament tears are graded 1, 2 or 3 (partial to complete), depending on how much the knee joint opens due to the ligament not holding it closed properly.

In general, any tear that results in instability while performing athletics (stress instability) or during normal daily activities (functional disability) can cause significant pain and additional injury to other knee structures (meniscus, articular cartilage). These results frequently require surgical intervention.


The symptoms of knee ligament injuries may include pain, swelling, and a feeling of the knee joint giving way. People with knee ligament injuries may have a decreased range of leg motion.


ACL (anterior cruciate ligament): The ACL is the major supportive ligament of knee, extending from the lower shin bone (tibia) to the thigh bone (femur). It primarily helps control knee movement by preventing forward motion and rotation of the tibia in relation to the femur.

Injuries to the ACL may occur from a twisting motion, such as running and changing direction suddenly during soccer or basketball, or direct contact or collision, such as with a football tackle. Some patients report hearing a popping noise when the ACL is injured and they are not able to continue the activity and may not be able walk. Pain may increase during the next 24 hours.

PCL (posterior cruciate ligament): The PCL is generally thought to be strongest ligament of knee and helps to control movement by preventing increased backwards motion and rotation of the tibia in relation to the femur. Injuries to the PCL usually don’t occur in isolation, but usually along with injury to another ligament. PCL injuries may result from “dashboard injuries” when the knee is pushed backward (hyper-extended) during a car accident or on-field collision.

MCL/LCL (medial collateral and lateral collateral ligaments): MCL and LCL ligaments are located, respectively, on the inside and outside of the knee joint. They provide stability against sideways stresses. MCL injuries occur with impact to the outside (lateral side) of the knee, pushing in the direction of the other knee (e.g. in a football tackle). Injury of the LCL occurs with excessive rotational stress or when force is exerted on the inside (medial side) of the knee and causes it to move in an outward motion. Injuries to MCL or LCL can occur along with ACL or PCL injuries.

Risk Factors

Risk for knee ligament injury stems from the sports activity and a person’s biomechanical deficiencies (e.g., weak hip or knee muscles). It is possible to be predisposed to knee-ligament injury, but usually such injuries are due to general trauma such as that occurring in cutting or pivoting movements. Some believe that the wearing of cleats may contribute to injury by causing a foot to stay planted in one direction when the knee turns the other way. ACL injuries happen more frequently in female athletes. This may be due to anatomical differences and/or possibly hormonal differences.


Diagnosis of knee-ligament injuries can be made by a qualified physician after obtaining a complete patient history and performing a thorough physical exam. The exam might include several tests to verify that the knee remains properly aligned through certain motions. The diagnosis may be confirmed by X-rays and an MRI (magnetic resonance imaging) of the knee.


Complications may include being unable to return to one’s sport or other activities due to pain or instability that precludes normal cutting, jumping, landing or acceleration. Pain or instability may also affect one’s ability to participate in general activities such as climbing stairs, hiking, and so on. Complications are quite rare after ligament-reconstruction procedures.


Patients with knee ligament injuries should apply the RICE (rest, ice, compression, elevation) principles. They should follow the physician’s and physical therapist’s instructions, as well as adhere to the recommended weight-bearing guidelines, such as using crutches and a brace. They should take oral medication as directed and avoid activities that cause pain.

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