Because the arthroscope and surgical instruments are thin, your surgeon can use very small incisions, rather than the larger incision needed for open surgery. This results in less pain for patients, less joint stiffness, and often shortens the time it takes to recover and return to favorite activities. During arthroscopy, your surgeon can see the structures of your knee in great detail on a video monitor.
For a function of three variables, a level set is a surface in three-dimensional space that we will call a level surface. For a constant value $c$ in the range of $f(x,y,z)$, the level surface of $f$ is the implicit surface given by the graph of $c=f(x,y,z)$.
In general, a tier (pronounced TEE-er ; from the medieval French tire meaning rank, as in a line of soldiers) is a row or layer in a series of similarly arranged objects. In computer programming, the parts of a program can be distributed among several tiers, each located in a different computer in a network. Such a program is said to be tiered , multitier , or multitiered . The 3-tier application model is probably the most common way of organizing a program in a network. N-tier applications (programs) are those that are tiered but the number of tiers isn't specified or may vary.