Diagnosing Pediatric ACL Injuries
A thorough clinical evaluation is the foundation of pediatric ACL diagnosis. Dr. Patel’s evaluation includes a detailed history of the injury mechanism, assessment of skeletal maturity using the Tanner staging scale, a baseline evaluation of limb alignment, and a systematic examination of both knees for comparison.
Key physical examination maneuvers include:
- Lachman Test: A test for anterior tibial translation with the knee at 20–30° of flexion — the most sensitive clinical test for ACL integrity. In children, muscular guarding in the acute setting often limits the accuracy of this test, and a repeat examination after pain and swelling have subsided may be more informative.
- Pivot-Shift Test: The pivot-shift test assesses rotational instability. Notably, the pivot-shift is positive in up to 98% of ACL-injured patients under anesthesia, but in conscious patients it reaches only 35% sensitivity — making it less useful in the clinic setting alone.
- Drawer Tests: Anterior and posterior drawer tests with internal and external tibial rotation provide additional information about ligamentous stability.
- Limb Alignment Assessment: Baseline assessment for any pre-existing limb length discrepancy or angular deformity is documented before any surgical planning.
In pediatric patients, documenting skeletal maturity is as important as confirming the ACL diagnosis. Management decisions — including whether to operate and which surgical technique to use — are directly dependent on the child’s skeletal age, not just their chronological age. Dr. Patel uses established tools for this assessment:
- Tanner Staging: Based on secondary sexual characteristics, providing a clinical staging of pubertal development
- Radiographic Bone Age (Greulich & Pyle): A radiograph of the non-dominant hand and wrist, interpreted using the Greulich and Pyle atlas or the Tanner-Whitehouse (TW3) method, provides an objective measurement of bone age
- Knee MRI Bone Age: Knee MRI itself can be used to estimate bone age through an atlas of skeletal development of the knee, recently validated to provide precise estimation of residual bone growth
- Long-Leg Alignment Radiograph: A full-length standing radiograph to identify any pre-existing deformity or limb length discrepancy before surgery is performed
MRI is the definitive imaging modality for suspected pediatric ACL tears, with sensitivity of 95% and specificity of 88% in pediatric populations. Beyond simply confirming the ACL tear, MRI provides critical information that directly guides treatment planning.
Primary MRI Findings in ACL Tears:
- Abnormal signal intensity within the ACL substance on T2-weighted sequences
- Discontinuity of the ACL fibers
- Blumensaat’s angle greater than 9.5° — indicating anterior displacement of the ligament remnant
Secondary MRI Findings:
- Lateral compartment bone bruise (present in approximately 70% of pediatric ACL tears)
- Anterior tibial displacement relative to the femur
- Uncovered posterior horn of the lateral meniscus
- Posterior cruciate ligament (PCL) angle less than 115°
ACL Tear Location Classification:
MRI also characterizes the level of the ACL tear, which has direct implications for surgical planning — particularly in determining whether primary ACL repair (rather than reconstruction) may be feasible. Using the Van Der List classification system, tears are categorized as proximal avulsion (>90% distal remnant), proximal (75–90%), midsubstance (25–75%), distal (10–25%), or distal avulsion (<10%).
Associated Injuries on MRI:
Meniscal and cartilage injuries frequently co-exist with pediatric ACL tears. MRI is the most accurate method for identifying these concomitant injuries, which influence the urgency of surgical intervention and the overall prognosis. The presence of a bone bruise without associated ACL injury is also commonly observed in pediatric patients, reflecting the unique cartilaginous composition of the growing knee. All MRI findings are carefully reviewed and discussed with patients and families as part of Dr. Patel’s comprehensive treatment planning process.
At a Glance
Ronak M. Patel M.D.
- Double Board-Certified, Fellowship-Trained Orthopaedic Surgeon
- Team physician to the Chicago Hounds (MLR) and past team physician to the Cavaliers (NBA), Browns (NFL) and Guardians (MLB)
- Published over 50 publications and 10 book chapters
- Learn more