The first thing to point out here is that most above knee prosthesis have an "endoskeleton" structure. In other words, below the socket the prosthesis looks like a human skeleton, and this narrow structure supports the amputee's weight. The other type is an "exoskeleton" where the bottom part of the leg looks like a leg; it is hollow and supports the weight of the amputee. This second type is old technology and the amputee should avoid it. Now, when you get an "endoskeleton" prosthesis, you will eventually need a covering that makes it look like a leg (at least in its shape).
Generally you do not want to cover the leg until you are fairly certain there is not a need for more adjustments (it is hard to adjust after the cover is put on). The adjustment period can last for several weeks/months after you get your leg. This means that you will have to walk around with a "thin leg" for a while until you are sure it is adjusted correctly. If you need adjustments after you get the cover, it generally can be done, but it is difficult and risks damaging the cover.
There are two types of covers, one-piece and two-piece covers. One-piece covers as the name suggest come in one piece. They have a kind of foam rubber content with a "skin" (the amputee has color choice) on the outside. This cover is fairly light and more than adequate to make the leg more life-like. The knee area does not always look just right because the one-piece cover tends to bend rather oddly around the knee unit (like when you sit down). These covers are not as durable as two-piece covers, but they tend to hold up pretty good.
The two-piece cover is generally made of a firmer material that as the name suggests is in two separate pieces. The two pieces join at the knee. The two-piece covers also tend to weigh more than one-piece covers. Generally the "knee break" looks better with a two-piece cover. The overall shape of the cover also looks better and holds the same shape better. The outside of the cover can be made to look very life-like too with a good artist.
How well your cover looks seems to vary depending on where you go to get the leg. Also, some amputees don't care too much for the cover looks, just as long as it makes the prosthesis look more leg-like through long pants. It is really a personal decision on how much effort you want in the cover. If any of the above knee amputees have information for AboveKneeAmputee.com™ about prosthesis covers (and where to get a really good cover), email us !!!!