Hairline fractures - how difficult is it to recognise them??

I will try to make it as short as possible but would really be interested in reading people's experiences on similar cases.

This is about a friend's horse which got kicked while out on a field and was found hopping lame (right front) in the evening. He had traces of blood on the leg just above the knee and a visible cut .
Owner took him to the vets, he had Xrays and scans done as well as joint fluid analysed as due to debris in the wound the vet anticipated infection in the joint itself. The latter proved negative but there seems to be no conclusion from any other procedures/checks!
They see no fracture, no soft tissue damage etc - yet the horse is hopping lame.
They decided to treat it as if there was a hairline fracture there and the horse's leg is now immobilised, wrapped up and he is cross-tied in his stable. He is to go back to the vets in two weeks.

Is this a normal practise. Two weeks sound awfully long to wait, especially because. this horse has just gotten to the end of the box rest with another injury -left front; tears on deep digital flexor tendon and bad navicular changes- and the vet's prognosis was very poor. They basically suggested PTS when they scanned him.

I had a look at the horse tonight and he is resting his weight on the "navicular" foot holding the "broken" one off the ground.

Is it really so hard to discover fractures?


Friend isn't sure whether to PTS or not as their vet isn't very helpful in their conclusions, suggestions, prognosis etc. The horse is made comfortable, looks alert and eats well.