Our patient is a very athletic 49 year-old female runner and triathlete who came to us for a 3D gait analysis. She complained of posterior-lateral knee pain, along with swelling at the back of her knee, medial to the locus of pain. She described the pain as going up and down during running. She denied any numbness or tingling.
The Challenge
The patient had seen multiple physical therapists who gave her knee strengthening exercises that did nothing to alleviate her pain. A previous MRI had revealed signs of patellofemoral dysfunction, mild chondromalacia, and a popliteal cyst on the medial knee that did not correlate with her pain.
Our Diagnostic Process
3D gait analysis
We performed a 3D gait analysis that identified multiple kinematic abnormalities, including:
Forward trunk lean of 15 degrees
Gluteal amnesia, affecting muscle coordination patterns and pelvic stability
Diagnostic Ultrasound
We performed a diagnostic exam using high-resolution ultrasonography, along with dynamic ultrasonography during running.
Ultrasound imaging revealed:
No knee instability
No bulging or meniscus
Avoidance of terminal knee extension
A popliteal cyst that had previously been detected on MRI
A small fabella – an accessory bone found in only about 5% of the population – that was not detected on MRI
We observed normal peroneal nerve movement through the fibular tunnel, but we noticed a snapping of the peroneal nerve against the fabella, which reproduced the patient’s symptoms.
Our Treatment
Our treatment protocol encompassed:
Personalized physical therapy to correct gait anomalies
Fascial manipulation to restore muscle gliding
Shockwave therapy using nano energy for the peroneal nerve and fabella
Peroneal nerve hydrodissection with 5% glucose to restore local nerve gliding and neuromodulation
The patient was symptom-free within 3 months.
Discussion
While most internal knee problems are well-visualized with MRI, the patient’s previous MRI exam did not detect the fabella, which we picked up on ultrasound. An important factor that distinguishes diagnostic ultrasound imaging from MRI is that the radiologist only examines the images, and not the patient. Moreover, ultrasound is superior for examining nerves compared to MRI. Because MRI images are static and not dynamic, they do not provide information about the dynamic interaction of various structures, in this case that of the peroneal nerve and the fabella.
In this instance, an athlete was originally diagnosed with minor quadriceps muscle strain and was treated for four weeks, with unsatisfactory results. When he came to our clinic, the muscle was not healing, and the patients’ muscle tissue had already begun to atrophy.
Upon examination using MSUS, we discovered that he had a full muscle thickness tear that had been overlooked by his previous provider. To mitigate damage and promote healing, surgery should have been performed immediately after the injury occurred. Because of misdiagnosis and inappropriate treatment, the patient now has permanent damage that cannot be corrected.
The most important advantage of Ultrasound over MRI imaging is its ability to zero in on the symptomatic region and obtain imaging, with active participation and feedback from the patient. Using dynamic MSUS, we can see what happens when patients contract their muscles, something that cannot be done with MRI. From a diagnostic perspective, this interaction is invaluable.
Dynamic ultrasonography examination demonstrating the full thickness tear and already occurring muscle atrophy due to misdiagnosis and not referring the patient to proper diagnostic workup
Demonstration of how very small muscle defect is made and revealed to be a complete tear with muscle contraction under diagnostic sonography (not possible with MRI)
Complete tear of rectus femoris with large hematoma (blood)
Separation of muscle ends due to tear elicited on dynamic sonography examination
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