The (deep) lateral femoral notch sign describes a depression on the lateral femoral condyle at the terminal sulcus, a junction between the weight-bearing tibial articular surface and the patellar articular surface of the femoral condyle. It is occasionally referred to as a deep sulcus sign, not to be confused with the deep sulcus sign in pneumothorax on supine CXR.
The likely mechanism is a hyperextension or impaction injury with a collision of the femoral condyle and the posterior tibial plateau during the rotational movement responsible for injuring the ACL, most commonly the pivot-shift.
Lateral femoral notch sign is usually first appreciated on the lateral radiograph and is suggestive of an osteochondral fracture 1,2. The depth of the lateral femoral notch sign has been shown to correlate with anterior cruciate ligament (ACL) tear 2.
A normal sulcus is located within 10 mm of Blumensaat's line on lateral projection 3.
On a lateral projection, a line is drawn from the normal articular surface of the lateral femoral condyle. The depth of the abnormal depression/notch can then be measured. A study compared the depth of the lateral femoral notch in patients with proven ACL tear and healthy individuals. A notch depth of 1.5 mm is shown as a useful additional sign of a torn ACL 2.
Internal derangement should also be suspected if the notch is irregular.
- 1. Pao DG. The lateral femoral notch sign. Radiology. 2001;219 (3): 800-1. Radiology (citation) - Pubmed citation
- 2. Cobby MJ, Schweitzer ME, Resnick D. The deep lateral femoral notch: an indirect sign of a torn anterior cruciate ligament. Radiology. 1992;184 (3): 855-8. Radiology (citation) - Pubmed citation
- 3. Warren RF, Kaplan N, Bach BR, The lateral notch sign of anterior cruciate ligament insufficiency. Am J Knee Surg, 1988;1:119-24.
Related Radiopaedia articles
The knee is a complex synovial joint that can be affected by a range of pathologies:
- bone and cartilage
- distal femoral condyle fracture
- tibial plateau fracture (classification)
- patella fracture
avulsion fractures of the knee
- arcuate complex avulsion fracture (arcuate sign)
- anterior cruciate ligament avulsion fracture
- biceps femoris avulsion fracture
- iliotibial band avulsion fracture
- patella fracture
- posterior cruciate ligament avulsion fracture
- reverse Segond fracture
- Segond fracture
- semimembranosus tendon avulsion fracture
- Stieda fracture
- chondromalacia patellae
- osteoarthritis of the knee
- osteochondral defects
- osteochondritis dissecans of the knee
- pattern of bone contusion in knee injuries
- knee fractures
- anterior cruciate ligament tear
- anterior cruciate ligament ganglion cyst
- anterior cruciate ligament mucoid degeneration
- posterior cruciate ligament tear
- medial collateral ligament tear
- lateral collateral ligament tear
- medial patellofemoral ligament tear
- posterolateral corner injury
- posteromedial corner injury
- meniscal lesions
- meniscal tear
- meniscal contusion
- meniscal/parameniscal cyst
- meniscal flounce
- meniscal fraying
- meniscal maceration
- meniscocapsular separation
- floating meniscus
- bursosynovial lesions
- fat pad
- popliteal fossa