Take a Knee
Answer: C
This boy likely has internal derangement of the knee, given his mechanism of injury, mild knee effusion, and incomplete examination due to edema. Internal derangement of the knee is often the preliminary diagnosis given
when there is a suspected injury to ligaments or meninsci associated with the knee joint (definitive diagnosis is limited by the acuity of the injury).
His plain films at first glance appear reassuring and would seem to prompt routine supportive care and follow-up (A, B). However, he has evidence of a particular finding: the lateral capsular sign (seen in the above image), indicative of a Segond fracture (Paul Segond, 1851-1912).
A Segond fracture is an avulsion of the lateral aspect of the proximal tibia below the articular surface, usually
from excessive internal rotation with varus stress, pulling on the lateral capsular ligament, as depicted here:
This boy likely has internal derangement of the knee, given his mechanism of injury, mild knee effusion, and incomplete examination due to edema. Internal derangement of the knee is often the preliminary diagnosis given
when there is a suspected injury to ligaments or meninsci associated with the knee joint (definitive diagnosis is limited by the acuity of the injury).
His plain films at first glance appear reassuring and would seem to prompt routine supportive care and follow-up (A, B). However, he has evidence of a particular finding: the lateral capsular sign (seen in the above image), indicative of a Segond fracture (Paul Segond, 1851-1912).
A Segond fracture is an avulsion of the lateral aspect of the proximal tibia below the articular surface, usually
from excessive internal rotation with varus stress, pulling on the lateral capsular ligament, as depicted here:
The main significance of a Segond fracture is that it is often accompanied by other injuries:
● Tear of the anterior cruciate ligament (75-100%)
● Injuries of the medial and lateral menisci (66-70%)
● Avulsion fracture of the fibular head
● Avulsion fracture of the Gerdy tubercle (proximal lateral tibia, a point of insertion for the iliotibial band)
In other words, the Segond fracture is a harbinger of major internal disruption and necessitates close orthopedic follow-up, mostly for evaluation of an occult anterior cruciate ligament tear (ACL). Occult ACL injuries are important to identify early, as minor tears may be treated conservatively; unidentified (and
therefore untreated) tears are at risk for complete tear, which significantly increases morbidity. Early identification of a likely significant co-injury can impact on this boy’s outcome and prospects for school and work.
His right knee should be immobilized and he should be non-weight bearing until he is seen by an orthopedic surgeon in 10-14 days (to allow for improvement of edema). If there is still suspicion of a concomitant injury such as an ACL tear, the specialist may decide to obtain advanced imaging such as MRI. A CT arthrogram is an alternative technique for those who have a contraindication to MRI (D).
References
Fuller MJ. Segond Fracture. Wiki Radiography. 2009.
Kalke RJ, Di Primio GA, Schweitzer ME. MR and CT arthrography of the knee. Semin Musculoskelet Radiol. 2012;16(1):57-68.
Sferopoulos NK et al. Avulsion fractures of the lateral tibial condyle in children. Injury. 2006; 37: 57-60.
Woods GW et al. Lateral capsular sign: x-ray clue to a significant knee instability. Am J Sports Med. 1979; 7(1):
27-33.
● Tear of the anterior cruciate ligament (75-100%)
● Injuries of the medial and lateral menisci (66-70%)
● Avulsion fracture of the fibular head
● Avulsion fracture of the Gerdy tubercle (proximal lateral tibia, a point of insertion for the iliotibial band)
In other words, the Segond fracture is a harbinger of major internal disruption and necessitates close orthopedic follow-up, mostly for evaluation of an occult anterior cruciate ligament tear (ACL). Occult ACL injuries are important to identify early, as minor tears may be treated conservatively; unidentified (and
therefore untreated) tears are at risk for complete tear, which significantly increases morbidity. Early identification of a likely significant co-injury can impact on this boy’s outcome and prospects for school and work.
His right knee should be immobilized and he should be non-weight bearing until he is seen by an orthopedic surgeon in 10-14 days (to allow for improvement of edema). If there is still suspicion of a concomitant injury such as an ACL tear, the specialist may decide to obtain advanced imaging such as MRI. A CT arthrogram is an alternative technique for those who have a contraindication to MRI (D).
References
Fuller MJ. Segond Fracture. Wiki Radiography. 2009.
Kalke RJ, Di Primio GA, Schweitzer ME. MR and CT arthrography of the knee. Semin Musculoskelet Radiol. 2012;16(1):57-68.
Sferopoulos NK et al. Avulsion fractures of the lateral tibial condyle in children. Injury. 2006; 37: 57-60.
Woods GW et al. Lateral capsular sign: x-ray clue to a significant knee instability. Am J Sports Med. 1979; 7(1):
27-33.