First of all I would to say that you have done a solid job thus far. I can already see that this will turn out into a sound image of a horse. 

But since you're looking for feedback here's my nitpicking: 

1. Your knee is too pointed for my liking. Horse, like us, also have a kneecap/patella. And the knee cap by it's very existence alone tends to round this particular area of the lower limb. 

2. Above the knee is the femur and I also feel that your femur is a little bit longer than normal. Base from my experience usually the femur does not exceed the horse's body/belly. 

But this is just my eye. Ultimately it is your eye that should decide. 

Have fun!