Precore-EFX556-Elliptical-Trainer will not put lot of strain on knees but properly planned and gradually increasing workout regime has to be followed.
Wrestling
golgi tendon organs
Some good ways to strengthen your knees would be to perform exercises which would strengthen the muscles around your knees. Low impact sports would help to build muscles on your knees as well.
Walking down-hill, especially with a heavy pack, puts a very high strain on your legs.
Spending a lot of time on your knees can cause pain after a while. Answer: spend less time on your knees.
No not normally
No, but it does cause other problems.
possible
No no no! Locking your knees while exercising in any way can cause joint problems and hyper-extension. Never lock your knees!
Yes
cause hes the bee's knees