Doctor's Notes on Torn Anterior Cruciate Ligament
(Torn ACL or ACL Injury)
ACL is an abbreviation for interior cruciate ligament, the most commonly injured knee ligament that helps to stabilize the knee. A torn ACL means the fibers that make up the ligament are broken or torn. Signs and symptoms are straightforward: the patient usually hears a loud popping sound as the ligament tears – pain is almost immediate in the knee and the knee swells within an hour or two. Walking becomes difficult and the knee feels unstable - the patient may have difficulty in extending or straightening the knee.
Causes of a torn ACL usually involve changing direction quickly, making a sudden stop or landing hard from a jump. In contact sports like football, the foot is usually planted and the knee is hyperextended and pivots at the same time causing the ACL to break and tear. Because of their anatomy, females are at higher risk for a torn ACL.
Torn Anterior Cruciate Ligament
(Torn ACL or ACL Injury) Symptoms
The patient usually can notice a loud popping sound as the ligament tears. Bystanders sometimes say that they can hear it as well. Pain is almost immediate. Knee swelling occurs within an hour or two as blood from the ruptured ligament fills the knee joint. Walking is difficult, and the knee feels unstable. Because of the fluid within the joint, it may be difficult to fully extend or straighten the knee.
Torn Anterior Cruciate Ligament
(Torn ACL or ACL Injury) Causes
In noncontact injuries, the person is usually changing direction quickly, making a sudden stop or landing from a jump. With the foot planted, the injured knee hyperextends (over straightens) and pivots at the same time, stressing the ACL and causing it to stretch and tear. In contact sports, the foot is usually planted and the blow causes knee hyperextension. High-risk sports include football, basketball, soccer, and skiing. The use of cleats also increases the risk of an ACL injury.
Women are at higher risk of sustaining an ACL injury than men. Potential reasons for this increased risk may include differences in anatomy, training, and activity experience. Genetic differences in how muscles contract may also be another reason for the increased risk in females. Furthermore, women have a wider pelvis than men to accommodate childbearing, and this can cause an increased angle where the femur meets the tibia at the knee joint (Q angle). A wider angle increases the stress on the ACL, increasing the risk of injury.
A narrow femoral notch may increase the risk of ACL injury especially in noncontact situations. The femoral notch is the space between the two femoral condyles that make contact with the tibial plateau in the knee joint. A narrow notch decreases the room where the ACL is located and can pinch the ligament during range of motion of the knee. This is especially true when the knee twists in hyperextension, potentially causing a tear in the ligament. Studies have also found that narrower notches are associated with smaller and potentially weaker anterior cruciate ligaments.
Women tend to have less muscle mass than men but tend to perform the same tasks, especially on the field of play. The male's larger quadriceps and hamstring muscle bulk tend to protect and stabilize better a women's quads and hamstrings, if the same stress is placed on the knee joint.
Sports injuries are injuries that occur when engaging in sports or exercise. Sports injuries can occur due to overtraining, lack of conditioning, and improper form or technique. Failing to warm up increases the risk of sports injuries. Bruises, strains, sprains, tears, and broken bones can result from sports injuries. Soft tissues like muscles, ligaments, tendons, fascia, and bursae may be affected. Traumatic brain injury (TBI) is another potential type of sports injury.
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.