Difficulty standing up from a squatting position? age or deconditioning?

Both: Unfortunately, one of earliest muscle groups to lose control of is the quads and hip flexors. These are the muscles needed to stand from a squatting condition. Deconditioning will also affect the same muscles. Fortunately, you can strengthen them with straight leg raises, exercise bicycle, and gentle (slow) stairclimbing.

Many possibilities: There are many problems that could give you trouble standing from a squatting position. If this is new onset and from muscle weakness deconditioning certainly could be the cause. Referred pain from the back or stenosis of the spine could also give you these types of symptoms. Pain in the front of the knee would be another common cause secondary to "patellofemoral" syndrome.