Anterior Cruciate Ligament Injury Workup

Updated: Jun 16, 2016
  • Author: Matthew Gammons, MD; Chief Editor: Sherwin SW Ho, MD  more...
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Workup

Laboratory Studies

Arthrocentesis

Blood with fat globules are indicative of an osteochondral or tibial fracture.

Tapping of the knee is rarely performed with the advent of other less invasive and more specific diagnostic tests (MRI).

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Imaging Studies

Plain radiographs

Radiographic findings are usually negative. Anteroposterior, lateral, merchant, sunrise, and notch views may be used by the physician to diagnose certain radiographic findings that are associated with ACL ruptures. Oblique radiographs may be helpful to exclude tibial plateau fractures.

The Segond fracture (lateral capsular avulsion fracture) may be visualized on an anteroposterior view. This is an avulsion fracture of the lateral tibial plateau, located near the joint line and posteriorly to the Gerdy tubercle. The Segond fracture represents a disruption of the meniscotibial portion of the lateral capsule. Segond fracture is direct evidence of a lateral capsule injury and indirect evidence of an ACL injury.

The lateral notch fracture (lateral view) is located in the lateral femoral condyle. This type of fracture is more commonly seen in chronic ACL-deficient knees, resulting from anterior subluxation of the lateral tibial plateau. The physician must differentiate lateral notch fractures from osteochondral defects or fractures.

Arthrograms

These studies have generally been replaced by MRI. Arthrograms are mostly of historical interest, having occasionally been used by physicians to diagnose ACL ruptures; they must be performed by a radiologist who is highly skilled in double-contrast arthrography.

MRI

MRI has a sensitivity of 90-98% for ACL tears. MRI also may identify bone bruising, which is present in approximately 90% of ACL injuries. An MRI allows the physician to confirm an ACL tear, but it should not be used as a substitute for a good history and physical examination. According to the Dutch Orthopaedic Association clinical guidelines for the treatment of ACL injury, MRI has no additional value when physical examination has shown anterior-posterior or rotational instability of the knee. However, MRI is reliable for establishing other intraarticular lesions. [16]

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Other Tests

See the list below:

  • Instrumented ligament testing
    • KT-1000 compares the difference in tibial excursion between the injured and the unaffected knee of a patient.
    • An excursion greater than 3 mm as measured by the KT-1000 is classified as pathologic.
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