Task: Question Answering
Input (English): Context: A couple months ago , I purchased a 12 year old TB mare from my old English teacher . She was lame at the time , but only a bit gimpy and the owner convinced me it was a stone bruise . I had my vet look at her , and it was , indeed , a stone bruise . Now a few months ( and probably a little over $ 1000 of xrays , joint supplements and everything later ) we ' ve come to find out she has navicular . 
Question: Why did they go to the vet ?
Output (English): They needed to diagnose what was wrong with their dog .