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Clinical Quiz Answer

Knee Pain, Swelling, and Instability

Deborah Cudnowski, MD
Peter J. Carek, MD, MS

THE PHYSICIAN AND SPORTSMEDICINE - VOL 31 - NO. 9 - SEPTEMBER 2003


Diagnosis

The anteroposterior (AP) x-ray shows a Segond fracture (an avulsed fragment of the proximal tibia) just below the lateral plateau (figure 2). With a Segond fracture, fibers of the iliotibial tract and anterior oblique band of the fibular collateral ligament are often attached to the avulsed fragment.1,2 An anterior cruciate ligament (ACL) tear caused this patient's instability.

The patient was discharged from the emergency department with a knee immobilizer and referred to our sports medicine office. The pain and swelling were reduced with rest, ice, and a nonsteroidal anti-inflammatory drug. He was given instructions for quadriceps strengthening and daily range-of-motion exercises, and he was referred to an orthopedic surgeon for further evaluation.

A Closer Look

Soft-tissue injuries, such as ACL tears and meniscal tears, often accompany bony knee injuries, but ligament injuries cannot be seen on x-rays. Evidence of a tibial avulsion, seen on AP x-rays, should alert clinicians to check for possible damage to the iliotibial tract and anterior oblique band. This case demonstrates the importance of knowing the mechanism of injury when proposing a differential diagnosis for knee injuries.

Originally described in 1879,1 the Segond fracture is an avulsion of the tibial condyle, just distal to the lateral plateau, at the insertion of the lateral capsular ligament. Studies1,2 suggest that fibers of the iliotibial band and the anterior oblique band of the fibular collateral ligament play an important role in the pathogenesis of the Segond fracture.

Injury mechanism. The proposed mechanism of injury is internal rotation of the tibia with the knee in flexion when a varus force is applied. In our case, the patient had his left foot planted and was turning to the left. His knee was bent, and the tibia was internally rotated (in relation to the femur) when he was tackled—a typical mechanism for a Segond fracture.

ACL tears occur in 75% to 100% of patients who have Segond fractures.1 In addition to ACL tears, 66% to 75% of patients also have meniscal tears. The incidence of ACL tears and meniscal injuries may contribute to the anterolateral rotational instability seen with clinical evaluation.2,3

Evaluation. Routine radiographs of the knee are adequate to make the diagnosis. A Segond fracture is best seen on the AP view as a small avulsed fragment just below the lateral tibial rim (see figure 2). Magnetic resonance imaging (MRI) will show bone edema at the avulsion (figure 3), but not necessarily the avulsed fragment.4 MRI helps identify evidence of associated ACL tears, meniscal tears, or other injuries. A thorough knee evaluation can identify additional injury, such as a posterolateral corner injury. In this case, a positive anterior drawer test and a Lachman's test were reliable signs of ACL disruption. A pivot shift test could also have been used, but it is less commonly performed.

Treatment. No specific treatment is recommended for a Segond fracture. Treatment focuses on the underlying injury; in this case, it was the ACL injury. Whether to manage a torn ACL conservatively or with surgery should be decided case by case. If surgery is performed, the patient will need rehabilitation for the ACL reconstruction to regain function.

References

  1. Segond P: Recherches cliniques et expérimentales sur les épanchements sanguins du genou par entorse. Progres Med 1879;7:297-299, 319-321, 340-341
  2. 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
  3. Davis DS, Post WR: Segond fracture: lateral capsular ligament avulsion. J Orthop Sports Phys Ther 1997;25(2):103-106
  4. Palmer WE: MRI evaluation of knee trauma, in Thrall JH (ed): Current Practice of Radiology. St Louis, Mosby-Year Book Inc, 1993, p 339


Dr Shea is a primary care sports medicine physician in the department of orthopedics at Kaiser Permanente in Sacramento, California. Dr Coppola is lead provider and a faculty member of the sports medicine fellowship program at Saint Vincent Sports Medicine Center in Erie, Pennsylvania, and a clinical professor at Michigan State University College of Osteopathic Medicine in East Lansing, Michigan. Address correspondence to Michael A. Shea, MD, via e-mail at [email protected].

Disclosure information: Drs Shea and Coppola disclose no significant relationship with any manufacturer of any commercial product mentioned in this article. No drug is mentioned in this article for an unlabeled use.


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