“The legs of the lame are not equal: so is a parable in the mouth of fools.”
This verse and verse 9 are very similar; both talk about worthlessness of wisdom given to fools. In this verse we see a parable compared to a crippled person’s legs. In verse 9 we will see a parable compared to a thorn in a drunk’s hand.
Before we go any further, let’s make sure we understand what a parable is. One dictionary defines a parable as “an extended metaphor or simile which compares a religious truth with a common experience or circumstance in life.”  But if that was too confusing, a parable is “a simple story used to illustrate a moral or spiritual lesson.” 
Jesus was famous for using parables to illustrate certain truths to His disciples. For example, you may remember the parables of the mustard seed (Matt. 13:31), the seed and the sower (Mk. 4:3), and the ten talents (Matt. 25). Each one was used to illustrate a point in such a way that the hearer could relate truth to a common experience.
Legs of the Lame
The King James version describes the legs of the crippled person as “not equal.” At first glance it may seem like Solomon is talking about one leg that is shorter than another. However, That “not equal” is another way of saying limp, worthless, or shriveled.
Imagine legs that have no strength, unable to bear the weight of the owner. They are deformed, curled under, twisted, and completely useless. Taking into account the original meaning of the Hebrew term (see Strong’s H1802), they may do nothing more than hang like string.
Parable In the Mouth of a Fool
Now, take the image of crippled legs that you have in your head and imagine them being a parable. How good is a parable that is incapable of illustrating truth? How good is a story that bears no resemblance to common experience? A parable like that can’t even stand on it’s own two feet.
How worthless, then, is the advice of a fool? What good is his counsel? Why should we listen to him?
Keep that in mind the next time you are offered emotional, spiritual, relational, and marital advice from someone who doesn’t even believe there is a God.
 David H. Wallace, “Interpretation of Parables,” ed. Ralph G. Turnbull, Baker’s Dictionary of Practical Theology (Grand Rapids, MI: Baker Book House, 1967), 107.
 Catherine Soanes and Angus Stevenson, Concise Oxford English Dictionary (Oxford: Oxford University Press, 2004).