David Pulton: A 26-Year-Old Registered Nurse With Posterolateral Knee Pain

Learning Objectives

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Learn the common causes of knee pain.
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Learn the common causes of fabella.
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Develop an understanding of the anatomy of the popliteal fossa.
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Develop an understanding of the differential diagnosis of fabella.
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Learn the clinical presentation of fabella.
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Learn how to examine the knee.
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Learn how to examine the popliteal fossa.
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Learn how to use physical examination to identify fabella.
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Develop an understanding of the treatment options for fabella.

David Pulton

David Pulton is a 26-year-old registered nurse with the chief complaint of, “It feels like I’ve got gravel in my knee and it really hurts.” David stated that his knee symptoms started after he was hit by a car when riding an electric scooter he rented while on vacation. “Doc, I’m really lucky I didn’t get killed. That guy really hit me. I was wearing a helmet, but he hit me so hard it knocked the helmet off and I hit my head on the pavement. I hit my head so hard it knocked me out. I was out for over an hour. I woke up in the emergency room at County with the worst headache I have ever had. I had a concussion and was off work for about 3 weeks. My head hurt so bad that I was pretty much in bed for a couple of weeks, so I really didn’t notice the pain and grating in my left knee until I was up and around.” I asked, “Tell me about the knee symptoms.” David just shook his head and said, “Doc, this may sound silly, but it feels like there is a piece of gravel in the back of my knee that is rubbing on everything and irritating it. The pain is not severe; it’s just always there, down deep, like the back outside of my knee is inflamed. It is really distracting because it never goes away.” I asked David what made it worse and he said that stairs were a real killer, as was squatting and being up on his feet during 12-hour shifts. “What makes it better?” I asked. “Doc, I am most comfortable when I have my leg up with a pillow under my knee with the knee slightly flexed. The heating pad helps, as does Motrin.”

I asked David how he was sleeping and he said, “Just okay. This whole thing has been very rough, and this knee keeps nagging at me.” I reassured David that I would do my best to sort out what was going on and get him better. “Just a few more questions and then let’s look you over. Any fever, chills, or other constitutional symptoms such as weight loss, night sweats, etc.?” David shook his head no. I asked David if he had ever had any previous left knee injuries and he again shook his head no.

On physical examination, David was afebrile. His respirations were 16, his pulse was 70 and regular, and his blood pressure was 120/70. David’s head, eyes, ears, nose, throat (HEENT) exam was normal, as was his cardiopulmonary examination. His thyroid was normal. His abdominal examination revealed no abnormal mass or organomegaly. There was no costovertebral angle (CVA) tenderness. There was no peripheral edema. His low back examination was unremarkable. Visual inspection of David’s knees was unremarkable; specifically, there was no ecchymosis, rubor, or obvious infection. Examination of his left knee revealed tenderness to palpation of the posterolateral border of the knee. There was a palpable grating sensation with flexion and extension of the left knee. Anterior and posterior drawer signs were negative, as were the valgus and varus stress tests ( Fig. 13.1 ). There was no obvious abnormal mass or bursitis; specifically there was no suggestion of a Baker cyst. There was no evidence of thrombophlebitis or pseudothrombophlebitis, and Homans sign was negative. A careful neurologic examination of the upper extremities was completely normal. Deep tendon reflexes were normal.

Key Clinical Points—What’s Important and What’s Not

The History

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A history of the onset of left posterolateral knee pain after being hit by a car
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A feeling like there is gravel in the knee
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A history of significant concussion
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No numbness
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No weakness
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No history of previous significant knee pain
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No fever or chills
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Sleep disturbance
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Pain on weightbearing and squatting
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Pain relief with elevation and flexion of the affected knee

The Physical Examination

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The patient is afebrile
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Tenderness on palpation of the left posterolateral knee
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Palpable grating sensation on flexion and extension of the right knee
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No evidence of knee instability with negative anterior and posterior drawer signs
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No evidence of knee instability with negative valgus and varus stress tests
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No abnormal mass noted
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No thrombophlebitis of pseudothrombophlebitis
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Negative Homans sign
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No obvious bursitis
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No obvious infection

Other Findings of Note

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Normal HEENT examination
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Normal cardiovascular examination
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Normal pulmonary examination
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Normal abdominal examination
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No peripheral edema
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Normal upper extremity neurologic examination, motor and sensory examination

What Tests Would You Like to Order?

The following tests were ordered:

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Plain radiographs of the left knee
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Ultrasound of the left knee
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Magnetic resonance imaging (MRI) of the left knee

Test Results

The plain radiographs of the left knee reveal a fabella with a complete transverse fracture ( Fig. 13.2 ). Ultrasound examination of the left knee reveals a large fabella ( Fig. 13.3 ). MRI scan of the left knee reveals a fabella with a low signal line consistent with a fracture ( Fig. 13.4 ).