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EM Cases: Occult Knee Injuries Pearls and Pitfalls

There are a whole slew of very important occult knee injuries – those that have a normal or near normal x-ray – that can cause serious morbidity if you miss them, and for the catchall soft tissue injuries there are some subtleties in diagnosis and management that will make a real difference to our patients...

When should we suspect a spontaneously reduced knee dislocation? Do all patients suspected of a spontaneous knee dislocation require a CT angiogram to rule out vascular injury? Which patients with a low energy mechanism are at risk for knee dislocation and vascular complications? How can you increase the accuracy of the active straight leg raise in assessing for quadriceps and…

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Featured

 Can I Tap That?

In the end, it seems as if we habitually slap a knee immobilizer or ACE bandage on knees, have the patients follow up with an orthopedic specialist, and hope for the best. Knee pain is such a frequent guest in our emergency department that we need to be prepared for its daily arrival. It is time to put an end to the pass off to orthopedics because the buck stops here and now in your ED. We are going to make you all experts by the end of this series on joint injuries and aspiration.

 Le Genou: Everything you Knee-d to know!

The acutely injured knee can often be challenging to assess when there is no associated fracture. Identifying the possible non-bony acute pathology is important to help discern the most appropriate approach to treatment for the patient.

 Ottawa Knee Rule

What pearls, pitfalls and/or tips do you have for users of the Ottawa Knee Rule? Are there cases when it has been applied, interpreted, or used inappropriately? As a general rule in the emergency department, x-rays are rarely useful because most injuries are soft tissue, and an x-ray does not show ligament injury.

Articles of Interest

Knee Immobilization for Acute Knee Injuries

Despite its common use, there is little evidence supporting rigid knee immobilization; in fact, numerous studies have illustrated its negative consequences, including thigh muscle weakness and atrophy, loss of motion, deep-vein thrombosis (DVT), and delay in return-to-sport or baseline activities. A 2020 study by Kilroe, et al suggests that atrophy and weakness are found within the first 2 to 5 days of knee immobilization, suggesting that even very brief periods of immobilization can have adverse effects.

Tips for Emergency Physicians on Spotting Occult Knee Dislocation

One of the differential diagnoses that we don’t often think about is that of the occult knee injury. A cognitive forcing strategy should be employed every time we are confronted with a patient who presents to the emergency department with a significant knee injury but has a normal or near normal X-ray:

Acute Knee Injuries: Use of Decision Rules for Selective Radiograph Ordering

Decision rules have been developed to reduce the unnecessary use of radiologic studies in patients with acute knee injury. The Ottawa knee rules and the Pittsburgh decision rules are the latest guidelines for the selective use of radiographs in knee trauma.

Can’t Miss Adult Knee Injuries

Most commonly injured joint of adolescent athletes...

Common Knee Injuries

The knee is a complex joint with many components, making it vulnerable to a variety of injuries. Some of the most common knee injuries include sprains, ligament tears, fractures, and dislocations. Many knee injuries can be successfully treated with simple measures, such as bracing and rehabilitation exercises. Other injuries may require surgery to correct.

Exam Series: Guide to the Knee Exam

Throughout the physical examination compare the asymptomatic to the symptomatic knee. The knee exam should be conducted with the patient supine, examining a knee in a chair or wheelchair can significantly compromise your exam! Every patient will have a different laxity to their joints at baseline, use the asymptomatic knee to get a sense of the patients baseline laxity. Pain with provocative movements without associated laxity suggests a ligament strain rather than a tear.

Occult Knee Injuries Pearls and Pitfalls

There are a whole slew of very important occult knee injuries – those that have a normal or near normal x-ray – that can cause serious morbidity if you miss them, and for the catchall soft tissue injuries there are some subtleties in diagnosis and management that will make a real difference to our patients.

Ottawa Knee Rules

The Ottawa Knee Rules determine the need for radiographs in acute knee injuries. This screening tool was developed because of the need for a rapid and accurate way to avoid unnecessary imaging.

The acutely injured knee in ED

Be aware that a painful knee may be referred pain from an injured hip or from L5 and S1 nerve roots which may be impinged as part of sciatica.

The Ottawa knee rules A useful clinical decision tool

Appropriate application of the rules can reduce the number of radiographs performed in the setting of acute knee injuries, with the potential benefits of improved cost efficiency and decreased radiation exposure for the patient.

Resources

2-Minute Knee Exam

Imaging is required to diagnose a number of important ED presentations. However, a thorough history and and physical exam can diagnose most causes of acute knee pain