About half of all injuries to the anterior cruciate ligament occur along with damage to other structures in the knee, such as articular cartilage, meniscus, or other ligaments. A “bruise” to the bone and cartilage of the femur and tibia occur nearly 100% of the time in acute ACL tears.
Injured ligaments are considered "sprains" and are graded on a severity scale:
- Grade 1 Sprains The ligament is mildly damaged in a Grade 1 Sprain. It has been slightly stretched, but is still able to help keep the knee joint stable.
- Grade 2 Sprains A Grade 2 Sprain stretches the ligament to the point where it becomes loose. This is often referred to as a partial tear of the ligament.
- Grade 3 Sprains This type of sprain is most commonly referred to as a complete tear of the ligament. The ligament has been split into two pieces, and the knee joint is typically unstable.
Partial tears of the anterior cruciate ligament are rare; most ACL injuries are complete or near complete tears (Grade 3).
Physical Examination and Patient History
During your first visit it is important to discuss your overall medical health, activity levels, hobbies and sports participation, and goals for the future, both professionally and in recreation. This will help determine the best treatment for your needs.
During the physical examination, your doctor will check all the structures of your injured knee, and compare them to your non-injured knee. Most ACL injuries can be diagnosed with a thorough physical examination of the knee in a relaxed patient.
Imaging tests are used to confirm the clinical diagnosis of an ACL tear:
- X-rays: Although ligaments can not be directly seen on xrays, they can show whether the injury is associated with a broken bone, particularly an avulsion of a small piece of bone that suggests an ACL tear, as in a Segond fracture, a small bony fleck avulsion off the proximal lateral tibia that corresponds with ACL tears. Xrays also reveal overall bony alignment of the knee and lower extremity, permitting the orthopedic surgeon to anticipate any required correction of bony alignment at the time of surgery. Additionally, in young athletes, xrays permit the surgeon to evaluate the growth plates, and select a surgical technique that will be safe for the patient and preserve growth of the long bones to the time of skeletal maturity.
- Magnetic resonance imaging (MRI) scan: MRI creates better images of soft tissues like the anterior cruciate ligament, and is the gold standard non-invasive test for confirming ACL tear. Accuracy of MRI in detecting ACL tears approaches 99%. MRI also permits full evaluation of the cartilage, meniscus, other ligaments, and other soft tissue, and if injury or tears to these other structures are present, they may be addressed simultaneously with ACL reconstruction or in future procedures. For instance, meniscus tears occur commonly with ACL tears, and rates of successful meniscus repair are higher when performed at the same time as ACL reconstruction than when performed alone. The meniscus (50% of multi-structure injuries), medial collateral ligament (30%), or articular cartilage (30%) are the most frequently concurrently injured structures.