Two Cases of Flexor Hallucis Longus Tenosynovitis With Highly Viscous Fluid Accumulation: The Role of Ultrasound Imaging.

Soft tissue injuries of the medial ankle including the flexor hallucis longus can be difficult to diagnose because of the complex functional regional anatomy. Flexor hallucis longus tenosynovitis is a relatively uncommon but well-described phenomenon in sports that require repetitive forefoot push-off in extreme plantar flexion. Although more work needs to be done to differentiate subtleties in imaging, identifying if the fluid can be easily compressed by sonographic pressure may help differentiate a typical flexor hallucis longus tenosynovitis from one with viscous, ganglion-like fluid. Here, we describe two cases of viscous flexor hallucis longus tenosynovitis that were resistant to treatment with regular care.