Susan had to be put into braces due to her weak knees.
I crawled through the forest on my hands and knees
i feel so weak today.
Infirm's synonym is weak so just use the common word weak in a sentence and replace it with infirm. For instance... My grandmother became weak with age. My grandmother became infirm with age. Voila! By doing that you just made a sentence for INFIRM.
My girlfriend's knees literally went weak when she first saw the jeweled tiara.
There are several ways to use formidable in a sentence. One sentence for formidable is; Walking on coals is a formidable challenge for anyone.
Her drug use will debilitate her family. That is a good sentence it means to make someone weak or make something be delayed.
After a week in bed with the flu, his face was ahsen and he felt weak.
The man was incapacitated by his weak heart, and therefore could not join the race.
If you are on your back with your hips and knees in flexion, your legs make a triangle with your knees at the peak.
The weak bridge toppled under the weight of the traffic.She had never felt so weak before.You are nothing but a weak little boy.She likes her juice a weak.Weak sounds like week, but has a different meaning.
Mine shafts are often weak and can collapse. After working for 48 hours without a break, he was about to collapse.
The dirt was ingrained in my knees due to all the playing the dirt I do.