Hi, I'm Dr. Jill. Since this may or may not be a sign of an issue, I would recommend having radiographs (x-rays) taken of any areas of concern, particularly these front feet. The radiographs would be read by the veterinarian in Spain taking them, but you could also take copies home to your regular veterinarian or a radiologist for an additional opinion.
Unfortunately no one will be able to predict with certainty Yunke's future performance, but this would give additional information as to the current health of these joints. If there is marked bony proliferation around joints indicating degenerative arthritic changes, then I suggest being more cautious about purchasing Yunke than if he has no signs of degenerative changes. Radiographs may also be able to help look at bone alignment and potential imbalances.
I hope this is helpful and gives you a potential direction. If you still have questions or concerns, please don't hesitate to ask. I would be glad to continue the conversation further.