  Joint bleeding is a common condition for people with hemophilia and, if
untreated, can result in hemophilic arthropathy. Ultrasound imaging has
recently emerged as an effective tool to diagnose joint recess distension
caused by joint bleeding. However, no computer-aided diagnosis tool exists to
support the practitioner in the diagnosis process. This paper addresses the
problem of automatically detecting the recess and assessing whether it is
distended in knee ultrasound images collected in patients with hemophilia.
After framing the problem, we propose two different approaches: the first one
adopts a one-stage object detection algorithm, while the second one is a
multi-task approach with a classification and a detection branch. The
experimental evaluation, conducted with $483$ annotated images, shows that the
solution based on object detection alone has a balanced accuracy score of
$0.74$ with a mean IoU value of $0.66$, while the multi-task approach has a
higher balanced accuracy value ($0.78$) at the cost of a slightly lower mean
IoU value.
