20yo high level soccer player complaining of click at posterior knee on leg extension 6 months post knee hyper extension injury.
The patient was asked to reproduce the click which was visualised under dynamic ultrasound assessment as the semitendinosus tendon compressing down and rolling over what was an atrophic appearing semimembranosus muscle (see first video below). The semimembranosus muscle was further assessed and a tear of the proximal tendon at musculotendinosis junction was noted. The tear had likely occurred as a result of the hyperextension injury as the patient had stated he felt hamstring discomfort post injury. This tear and subsequent scarring has lead to lengthening of the proximal tendon and loss of normal muscle function leading to muscle atrophy.
ST tendon flicking over SM on leg extension.
Running through SM from its origin distally you can see the disrupted tendon at the proximal MTJ followed by the atrophic muscle belly (tear is evident deep to ST raphe).
Proximal SM MTJ tear with a comparison showing normal right side with easily distinguished tendon fibres.