Not a problem in my big winter boots but with today’s warmth and summer shoes I’ve got a sore knee and thigh.
According to my yoga teacher she reckons it’s because I don’t keep my legs straight.
Any ideas on how to correct this problem?

keep your legs straight ?

(how/why is it not a problem in winter boots?)

[url=https://flic.kr/p/ovKQjo]Suffolk Hols 2014[/url] by matt_outandabout, on Flickr

Footbeds, wedges, cleat wedges.

Winter boots have ankle support I guess.
When riding my bike on the turbo I used to get the same soreness and I always wore summer shoes when using it.
Mr Smith ,is it trial and error with those items or can you be fitted for them?

Concentrate on keeping your hips in line with your knees and your knees above your feet during pedaling.

If you still feel your knees are pointing outwards consciously try to hit the top tube with your knees while peddling, this is of course an exaggeration and riding full-time like this is the equivalent of riding knock kneed (which is also bad form) but as a temporary measure to correct splaying knees it worked for me.

Quite a few folk I see out riding with their knees bowed out don’t have their seat anything like high enough. Maybe look at seat height.

That too, if your seat is too low it’s easy to splay your knees, much harder to do with a seat set high enough and getting full leg extension.

Mr Smith ,is it trial and error with those items or can you be fitted for them?

Depends if you pronate or supinate, most footbeds for cycling are to fill the arch and bring your knee away from the top tube and to track straight (your feet flatten out without orthotics and your knee will move inwards).
So you need custom footbeds and shims inside the shoe and cleat wedges, though I would imagine just a cleat shim would help. Like this but used the other way