Do you really mean Salix caprea, or a cultivar of it? It's just that Salix caprea gets 50 feet by 33 feet wide, so I'm going to assume you have the "Kilmarnock Willow" cultivar, a small, standard, weeping tree. If that tree has been in the pot for five years, the likelihood is that its now completely rootbound and needs more space to spread - 5 years in a large pot probably is about as far as you can go, and the tree should really now be in the ground, assuming it hasn't died already.

Many thanks for your reply. You could be right about it being pot bound. I have just said to my husband he should change the soil and put in fresh compost. It is not very tall about 8ft with small pink/white leaves. Its not like the one in your picture. Thank you again for your reply. Lynda

Pink white leaves sounds like Salix integra 'Hakuro-Nishiki' - repot, as you say, but put in a larger pot if you can.

Yes I will definitely repot. Many thanks for your help. Lynda

You can repot into the same pot.
Remove from pot and wash off old soil with a hose pipe.
tease out long circling roots and cut them off.
remove 1/3 of the thick roots in the rootball (this will encourage fine feeder roots to develop) remembering to leave thick surface roots.
cut back remaining roots so that it fits into the pot with room to spare.
place fresh compost into bottom of pot, add tree rootball, fill in surrounding space taking care to push compost into all areas of the rootball leaving no air spaces.
water well and keep out of full sun to allow the tree to recover.
If you plan to do this when the tree is in full leaf you can help the tree recover by cutting off the leaves leaving the leaf stalk which will encourage the buds to open later.
Feed one month after buds have opened.
Keep the tree trimmed to a suitably managable size.
Willows are vigorous thirsty trees so this repot needs to be done yearly.
I hope this helps. If it doesn't at least it gave you something to read. ;-)