The anterior cruciate ligament, also known as the ACL, is one of the major ligaments within the knee joint. The ligament connects the femur and tibia bones, providing stability to the
knee and preventing over-bending and over-straightening. An ACL tear can refer to any injury caused to the
ligament, from a minor sprain to a true tear.
ACL tears are one of the most common types of sports injuries, and are typically caused by motions that apply twisting forces on the knee such as pivoting one one foot or stopping suddenly. Sports like football or soccer that involve such motions along with physical contact are more prone to causing ACL tears. ACL tears can also be received from non-contact sports related
injuries, like landing from a jump, running, pivoting, or overextending the knee joint.
ACL Tear Symptoms
Symptoms of an ACL tear will vary based on how severe the tear is and whether or not additional injuries were received alongside the original injury.
Pain – Sudden onset of severe knee pain is common with an ACL tear.
Injury onset typically begins with a sharp, stabbing pain on the outside and back of the knee, which over time may become
a throbbing ache. Movements like straightening or bending the knee will increase the amount of pain.
‘Pop’ sound – Patients typically describe a “popping” sound or sensation in their knee when the injury occurs. This sound is typically followed by intense, sharp pain in the knee.
Swelling – Swelling, also known as hemarthrosis, starts to occur almost immediately after the ACL is torn and tends to persist if the injury is left untreated. This swelling is the result of irritation to the knee joint due to disruption of the ACL. This irritation causes the knee joint to fill with blood, causing the swollen knee to lose range of motion and appear puffy and large.
Loss of Strength and Instability – The ACL provides stability to the knee. When an injury to the ACL occurs, the knee joints may become unstable with certain motions. Minor tears tend to cause
instability while jumping or pivoting, while major ACL tears can cause difficulty moving around and a sensation that the knee will “give way”.
Limited Movement – Because the knee swells and tends to cause extreme pain with movement, ACL tears typically reduce the range of motion in the injured knee and leg.