What's the diagnosis? By Dr. Angela Ugorets
A 26 yo male presents to the ED with severe left leg pain after he slid into home plate during a softball game. He was unable to get up and walk afterward. He has an obvious left lower extremity deformity. An x-ray is shown. What's the diagnosis? Scroll down for answer.
Answer: Anterior knee dislocation
- Usually the result of high force injury like MVC ("dashboard knee"), can also occur during sports (hyperextension) or with minor trauma in the morbidly obese
- Feared complicatirons are popliteal artery injury (~1/3 of dislocations) and peroneal nerve injury
- popliteal artery is tethered in the popliteal fossa behind the knee
- Pain control and neurovascular exam - check and document dorsalis pedis and posterior tibial pulses
- X-ray (at least 2 view)
- Reduction (splint in 20 degrees of flexion)
- ABI - ankle brachial index*
- Most specialists will also recommend CTA of leg
- Orthopedics consultation (+/- vascular depending on result of ABI and CTA)
- Admission for serial neurovascular checks
- Pitfall: some patients may come to the ED after dislocation and spontaeous reduction, exam will be an unstable knee; do not miss an occult popliteal artery injury, patient requires x-ray, ABI, splinting, CTA, and orthopedics evaluation
Over-inflate the BP cuff on the arm, place the doppler over the brachial artery, deflate the cuff slowly until you hear the doppler sound of the brachial artery pulse. This is the systolic pressure.