My husband for the past year has had a constant pain in his knee he can barely walk he cannot bend his knee is a sharp achy pain he was getting off the ladder one day at work and his knee buckled it is all on the sides of his knee the back?

No way for a distant forum doctor to know. He needs to see an orthopedist.

Not feasible to be precise without a thorough direct examination. Orthopedic surgical consultation is definitely indicated, and prolonged delay is unlikely to result in spontaneous improvement at this point.

Buckling is usually the sign of an internal mechanical derangement such as a torn meniscus. I would skip seeing his primary doctor and see an orthopedic surgeon.