Your problem mostly could be a meniscal tear.The meniscal tears are not evident in x ray.It need an mri to find out.And if it is there you might need an arthroscopy
for further diagnosis and treatment like meniscectomy.Peripheral vascular disease
possibility you should rule out by doppler usg.Varicose vein
in first stages the veins wont be prominent.Only you can have an edema and pain after excertion.Probably you will get that in eveninings.
First you should consult an orthopedician.he will give you a consultation with general surgeon
to rule out varicose or peripheral vascular disease if necessary.
Wishing you a fast recovery