I have been a hairdresser for 5 years, and before that was a server for 10. I am used to standing for long periods. I want to do the right exercise to strengthen my legs, especially my knees to keep my legs free from pain and injury. Maybe a specific sport? Right now I do ballet and yoga. What would be especially beneficial?

I have been a hairdresser for 5 years, and before that was a server for 10. I am used to standing for long periods of time. I want to do the right exercise to strengthen my legs, especially my knees to keep my legs free from pain and injury. Maybe a specific sport? Right now I do ballet and yoga. What would be especially beneficial?
As you are already doing some good exercises(yoga/dance). Think you should streach you knees

I have found walking about 3 miles a day increases my standing stamina.