Knee muscles?

Most of us woke up this morning expecting aches and pains from the weekend's 'workout'. But thankfully, I don't feel so bad! :0) I thought my knees would ache like hell considering it was my most used body part over the 2 days of boarding. Without exaggerating, I've never worked a body part SO hard in my life. At one point, my heart was beating outta my chest and I literally felt like my knees were going to buckle and I would just tumble 'free-falling' style all the way down to the base. Ha. For those of you who are unfamiliar with snowboarding, your knees are used for braking. And oh boy, did I. There were parts of the mountain that were too steep for me so I ah, just kept using my knees. Ha. So... the question. Do knee muscles exist?? I'm not sure if its an indication of me becoming fitter or in reality, I'm not working out as hard as before, cos I don't feel so achy and sore anymore. I sure hope its the former! With a weekend of boarding on our record, Lucy and I kept up with the momentum and went for gym class today. To continue working those knee muscles..