"which body cavity would be opened for a total knee joint replacement"

Answer;

-Synovial cavity

Explanation;

-The synovial cavity/joint is filled with synovial fluid. A synovial joint contains a synovial cavity and dense, irregular connective tissue that forms the articular capsule normally associated with accessory ligaments.

-A synovial joint occurs at articulating bones to allow movement. It is distinguished by a surrounding synovial capsule.The bones of a synovial joint are surrounded by a synovial capsule, which secretes synovial fluid to lubricate and nourish the joint while acting as a shock absorber.

cuz he is really really short, assuming an unorthodox and inherently unlucky configuration of elevator buttons…

explanation:

yes we can.   a lady urinates from her urethra.