Segond Fracture

1. High-Yield Overview & Pathognomonic Essence

• Morphological Hallmark: The Segond fracture presents on plain radiography as a subtle, vertically oriented, curvilinear or elliptic cortical bone avulsion fragment (1 to 3 mm in thickness, 8 to 10 mm in length) originating from the anterolateral tibial plateau margin, 3 to 4 mm distal to the lateral articular surface, positioned midway between Gerdy’s tubercle and the fibular head.
• Pathognomonic Significance: Represents a tensile bony avulsion of the anterolateral complex (specifically the anterolateral ligament and the mid-third lateral capsular ligament), serving as a pathognomonic radiographic indicator of complete anterior cruciate ligament (ACL) rupture with 95% to 100% positive predictive specificity.
• Critical Surgical Implication: Identification of this seemingly trivial cortical flake heralds severe multi-ligamentous disruption and anterolateral rotatory instability (ALRI); it mandates prompt magnetic resonance imaging to assess associated meniscal pathology and warrants consideration of concurrent lateral extra-articular tenodesis (LET) or anterolateral ligament (ALL) reconstruction during ACL reconstruction.

2. Diagnostic Sign Summary Matrix

3. Clinical Case Imaging & Standardized Figures

4. Pathophysiology & Biomechanical Mechanism

The Segond fracture was first characterized in 1879 by the French surgeon Dr. Paul Segond following clinical observations and post-mortem cadaveric experiments on traumatic joint effusions. Segond observed that forced internal rotation combined with knee flexion consistently provoked a tense, pearly fibrous band at the anterolateral joint margin to detach an osseous fragment from the lateral tibial margin. Modern anatomical and biomechanical investigations have refined this anatomical substrate: the fracture represents a true bony avulsion of the anterolateral ligament (ALL) of the knee, accompanied by variable detachment of the mid-third lateral capsular ligament and deep fibers of the iliotibial tract.

The anterolateral ligament originates immediately proximal and posterior to the lateral femoral epicondyle, coursing obliquely distally and anteriorly across the joint line to insert robustly onto the anterolateral tibial plateau. The insertion footprint lies midway between the anterior prominence of Gerdy’s tubercle and the posterior projection of the fibular head, located approximately 3 to 4 mm distal to the lateral articular surface. Biomechanically, the ALL functions as an essential secondary stabilizer against internal tibial rotation and anterior tibial translation, working in direct synergy with the primary intra-articular restraint, the anterior cruciate ligament.

The biomechanical mechanism generating the Segond fracture involves a violent pivot-shift episode during non-contact deceleration, sudden change-of-direction, or landing from a jump. The knee experiences a triad of excessive internal tibial rotation, acute knee flexion (predominantly between 30° and 60°), and dynamic valgus loading. Under these catastrophic kinematics, the intra-articular ACL undergoes structural tension failure. As the primary restraint ruptures, the lateral tibial plateau subluxates anteriorly relative to the lateral femoral condyle, transferring immense rotatory and distraction forces to the secondary anterolateral restraints. When tensile stress along the ALL insertion footprint exceeds the ultimate shear strength of the subchondral cortical bone, a thin flake of cortical bone avulses. This avulsion relieves soft-tissue tension within the mid-substance ligament, explaining why the avulsed fragment remains anchored to the intact distal ALL fiber bundle.

5. Modality-Specific Imaging Findings

Plain Radiography

On standard anteroposterior (AP) radiographs of the knee, the classic Segond fracture appears as a small, vertically elongated, elliptic or curvilinear cortical bone flake measuring 1 to 3 mm in thickness and 8 to 10 mm in longitudinal dimension. The fragment is situated adjacent to the lateral margin of the proximal tibial plateau, approximately 3 to 4 mm distal to the joint line. It runs parallel to the lateral tibial cortex, separated by a thin radiolucent gap representing the donor defect. Because the fracture is aligned obliquely along the anterolateral curvature of the tibial condyle, it can be obscured on true AP views by overlapping cortical contours.

To optimize visualization, an internal oblique projection of the knee (rotated 15° to 20° internally, often termed the specialized “Segond view”) projects the anterolateral tibial plateau in profile and profile-tangent to the x-ray beam, dramatically improving diagnostic sensitivity for subtle or minimally displaced flecks. On the lateral radiographic projection, associated secondary findings include the “deep sulcus terminalis sign”—an impaction depression exceeding 1.5 to 2.0 mm in depth within the lateral femoral condyle terminal sulcus (groove between the weight-bearing condyle and patellar articular surface)—caused by violent impaction of the lateral femoral condyle against the posterior lateral tibial plateau during the pivot-shift event. Cross-table lateral radiographs frequently demonstrate a lipohaemarthrosis (fat-fluid level) within the suprapatellar pouch, confirming intra-articular cortical disruption.

Computed Tomography

Thin-slice multiplanar computed tomography (CT) with 2D coronal, axial, and 3D volume-rendered reconstructions provides precise anatomical delineation of the avulsed fragment and donor site. CT accurately differentiates the Segond avulsion from depressed lateral tibial plateau fractures (Schatzker type II or III), confirming the complete absence of articular surface step-off, central comminution, or subchondral impaction.

On axial CT slices, the osseous fragment is localized precisely along the anterolateral cortex of the tibia, positioned intermediate between the anterior tuberosity of Gerdy’s tubercle and the posterior margin of the fibular styloid. Coronal CT reconstructions demonstrate the vertical orientation of the fragment and quantify bony displacement. Multiplanar CT also permits exact measurement of fragment volume, assisting the surgeon in deciding whether the osseous fragment is amenable to primary suture anchor fixation or headless screw fixation versus soft-tissue tenodesis.

Magnetic Resonance Imaging & Ultrasound

Magnetic resonance imaging (MRI) is the definitive diagnostic modality for evaluating the full spectrum of soft-tissue and osseous pathology associated with the Segond fracture. High-resolution coronal and axial intermediate-weighted fat-suppressed (proton density [PD] FS) and T2-weighted FS sequences reveal focal discontinuity or complete detachment of the low-signal fibrous bands of the anterolateral ligament at its tibial insertion footprint, surrounded by high-signal periligamentous fluid and capsular edema.

MRI universally demonstrates the pathognomonic “pivot-shift bone marrow contusion pattern.” This pattern manifests as extensive high-signal trabecular edema on fluid-sensitive sequences involving the posterior-inferior margin of the lateral tibial plateau and the middle third of the lateral femoral condyle (sulcus terminalis). MRI also allows comprehensive evaluation of concomitant intra-articular derangements: complete tear of the anterior cruciate ligament (present in 95% to 100% of cases), peripheral tears of the posterior horn of the lateral meniscus, meniscocapsular separations, meniscal ramp lesions, posterior meniscal root tears, and associated medial collateral ligament (MCL) sprains.

On high-frequency musculoskeletal ultrasound (12 to 18 MHz linear transducer), the Segond fracture manifests in the coronal-oblique plane as a discrete, hyperechoic cortical disruption with posterior acoustic shadowing adjacent to the anterolateral tibial articular margin. Real-time dynamic sonographic assessment with gentle internal rotation stress reveals laxity or widening of the avulsion gap and confirms disruption of the fibrillar architecture of the ALL.

6. Diagnostic Utility, Sensitivity & Specificity

The diagnostic utility of the Segond fracture centers on its exceptional specificity. Multiple prospective and retrospective correlation series establish that radiographic identification of a Segond fracture carries a specificity between 95% and 100% for an underlying complete tear of the anterior cruciate ligament. In the classic series by Goldman et al. (1988), 100% of patients exhibiting a Segond fracture on plain radiographs had an arthroscopically confirmed complete ACL rupture. Similarly, Hess et al. (1994) corroborated this exclusive correlation in a comparative cohort study, establishing that a Segond fracture is virtually never encountered in the presence of an intact ACL unless extraordinary isolated trauma has occurred.

Despite its exquisite specificity, the sensitivity of the Segond fracture on standard plain radiographs is modest, ranging from 9% to 12% in unselected acute ACL rupture populations. This sensitivity increases to approximately 15% to 20% on thin-slice CT or dedicated multiplanar MRI, as non-displaced or purely cartilaginous/periosteal avulsions become detectable. The positive predictive value (PPV) of the sign exceeds 98%, while the negative predictive value (NPV) remains low (25% to 30%). Therefore, the absence of a Segond fracture can never be used to rule out an ACL rupture. However, the presence of this sign transforms a suspected “simple knee sprain” into a definitive high-grade multi-ligamentous disruption requiring urgent orthopaedic consultation.

7. Differential Diagnosis & Radiographic Mimics

Several distinct avulsion fractures and periarticular bone lesions around the knee joint can mimic or be confused with a classic Segond fracture. Distinguishing these entities requires rigorous anatomical localization, correlation with underlying ligamentous injury vectors, and appropriate cross-sectional imaging.

8. Clinical Significance & Management Implications

The clinical identification of a Segond fracture carries paramount therapeutic consequences that fundamentally alter the diagnostic workup and surgical strategy for the injured knee:

• Mandatory Advanced Diagnostic Evaluation: Discovery of an anterolateral cortical fleck on acute knee radiographs mandates prompt high-field magnetic resonance imaging. Clinicians must recognize that the patient has suffered a high-energy rotatory ligamentous catastrophe rather than an isolated osseous chip, necessitating immediate immobilization in a hinged knee brace and early subspecialty orthopaedic consultation.
• Surveillance for Concomitant Meniscal Pathologies: Concomitant meniscal tears are documented in 65% to 75% of patients with Segond fractures. Lateral meniscal tears (predominantly posterior horn tears, peripheral detachments, and root avulsions) predominate over medial meniscal pathology (45% vs. 20%). During reconstructive arthroscopy, meticulous probing of the lateral meniscal root and the posteromedial ramp zone is essential to address hidden meniscal instability.
• Resolution of Anterolateral Rotatory Instability (ALRI): The presence of a Segond fracture signifies structural incompetence of the anterolateral capsuloligamentous restraint. In an ACL-reconstructed knee, unaddressed deficiency of the anterolateral complex leaves residual anterolateral rotatory subluxation (a persistent grade II or III pivot shift). Biomechanical investigations demonstrate that this residual rotatory laxity exposes the intra-articular ACL graft to excessive tensile strains, leading to progressive graft attenuation and catastrophic reconstruction failure.
• Indications for Lateral Augmentation Procedures: Large prospective clinical trials—notably the SANTI study group findings published by Sonnery-Cottet et al. (2017)—demonstrate that augmenting primary ACL reconstruction with an anterolateral procedure (either combined Anatomic Anterolateral Ligament Reconstruction or a Lateral Extra-Articular Tenodesis [modified Lemaire]) reduces the rate of ACL graft rupture by more than 2.5-fold. Current surgical consensus strongly recommends lateral extra-articular stabilization in the setting of an acute Segond fracture, high-grade pivot-shift laxity, revision ACL surgery, or high-demand young pivoting athletes. If the avulsed Segond fragment is large (> 10 to 15 mm) and significantly displaced, acute open or arthroscopic reduction and internal fixation utilizing suture anchors or miniature headless compression screws can be performed concurrently.

9. Master Class Pro-Tip

Master Class Pro-Tip: Never dismiss a subtle 1-to-3-millimeter vertical elliptic cortical fleck along the anterolateral tibial plateau as a minor sprain or inconsequential avulsion. On plain radiography, the Segond fracture is an all-or-nothing sign: it reflects catastrophic tensile failure of the anterolateral complex during a high-energy pivot-shift injury, accompanied by complete anterior cruciate ligament rupture in over 95% of cases. When identified, obtain immediate high-resolution MRI to evaluate concomitant lateral meniscal root avulsions and ramp lesions. In young active patients undergoing ACL reconstruction, the presence of a Segond fracture is a definitive indication to perform a concurrent lateral extra-articular stabilization (modified Lemaire tenodesis or anatomic ALL reconstruction). Adding lateral extra-articular restraint restores rotational kinematics, shields the primary intra-articular graft against excessive shear forces, and reduces ACL revision rates by more than half.

Master Class Radiological Pearl: Segond Fracture and Anterolateral Instability

10. Evidence-Based Synthesis

11. References

1. Segond P. Recherches cliniques et expérimentales sur les épanchements sanguins du genou par entorse. Progrès Médical. 1879;7:297-299, 319-321, 340-341. [Level V: Classic Historical Description / Cadaveric Investigation]
2. Hess T, Rupp S, Hopf T, Gleitz M, Liebler J. Lateral tibial avulsion fractures and disruptions to the anterior cruciate ligament. A clinical study of their incidence and correlation. Clin Orthop Relat Res. 1994;(303):193-197. DOI [Level III: Retrospective Comparative Cohort Study]
3. Claes S, Luyckx T, Vereecke E, Bellemans J. The Segond Fracture: A Bony Injury of the Anterolateral Ligament of the Knee. Arthroscopy. 2014;30(11):1475-1482. DOI [Level V: Anatomical Dissection & Radiographic Study]
4. Goldman AB, Pavlov H, Rubenstein D. The Segond fracture of the proximal tibia: a small avulsion that reflects major ligamentous damage. AJR Am J Roentgenol. 1988;151(6):1163-1167. DOI [Level IV: Retrospective Observational Study]
5. Dietz GW, Wilcoxson J, Montgomery JB. Segond tibial condyle fracture: lateral capsular ligament avulsion. Radiology. 1986;159(2):467-469. DOI [Level IV: Retrospective Radiographic-Arthroscopic Series]
6. Campos JC, Chung CB, Lektrakul N, et al. Pathogenesis of the Segond Fracture: Anatomic and MR Imaging Evidence of an Iliotibial Tract or Anterior Oblique Band Avulsion. Radiology. 2001;219(2):381-386. DOI [Level V: Cadaveric Anatomic & Clinical MR Investigation]
7. Sonnery-Cottet B, Saithna A, Cavalier M, et al. Anterolateral Ligament Reconstruction Is Associated With Significantly Reduced ACL Graft Rupture Rates at a Minimum Follow-up of 2 Years: A Prospective Comparative Study of 502 Patients From the SANTI Study Group. Am J Sports Med. 2017;45(7):1547-1557. DOI [Level II: Prospective Comparative Cohort Study]
8. Escobedo EM, Mills WJ, Hunter JC. The “Reverse Segond” Fracture: Association with a Tear of the Posterior Cruciate Ligament and Medial Meniscus. AJR Am J Roentgenol. 2002;178(4):979-983. DOI [Level IV: Retrospective Cohort & Imaging Review]