The anterior cruciate ligament (ACL) is a band of tough connective tissue located deep within the knee joint, connecting the thighbone (femur) to the shinbone (tibia). Its primary function involves stabilizing the knee, particularly by preventing the shinbone from sliding too far forward and limiting rotational movements. ACL tears are common injuries, especially in sports that involve sudden stops, changes in direction, or awkward landings. Understanding the signs of an ACL injury can help in seeking timely medical attention.
Immediate Signs and Symptoms
An ACL tear often presents with distinct immediate signs. A loud “pop” or a popping sensation is felt or heard in the knee at the moment of injury. This is followed by sudden and severe pain within the knee joint, which can make it difficult to continue the activity.
Rapid swelling develops within minutes to a few hours as blood fills the joint space, often making the knee appear noticeably larger. A feeling of instability, or the knee “giving way” under weight, is also common, making it challenging or impossible to bear weight on the affected leg.
Later Signs and Symptoms
Symptoms can evolve or persist in the hours and days following an ACL injury. Persistent swelling around the knee joint is common, which may fluctuate in intensity or worsen over time. Bruising around the knee can become visible a day or two after the injury, indicating internal bleeding.
Continued instability, particularly during movements like twisting, pivoting, or walking on uneven surfaces, becomes more apparent. While initial severe pain may subside, a dull ache or throbbing discomfort can persist, flaring up with certain activities. A reduced range of motion, making it difficult to fully straighten or bend the knee, is another common later symptom.
What to Do After Suspecting an ACL Tear
If an ACL tear is suspected, seeking prompt medical attention is important. Consulting a doctor, an orthopedic specialist, or visiting an urgent care clinic can ensure a proper diagnosis and guide the next steps. Early evaluation can help prevent further damage to the knee.
While awaiting medical evaluation, initial self-care measures can help manage pain and swelling. The R.I.C.E. protocol is recommended: Rest the injured knee by avoiding weight-bearing activities. Apply Ice to the affected area for 15-20 minutes at a time, several times a day, using a thin towel between the ice and skin. Apply Compression with an elastic bandage to help reduce swelling, ensuring it is snug but not too tight. Elevate the injured leg above heart level as often as possible to aid fluid drainage.
A healthcare provider will perform a physical examination, including specific tests like the Lachman test, to assess the knee’s stability and ligament integrity. Magnetic Resonance Imaging (MRI) is used to confirm an ACL tear and identify any other associated knee injuries, such as meniscus or other ligament damage. A professional diagnosis is important for developing an appropriate treatment plan, as self-diagnosis cannot fully determine the extent of the injury.