The body has many joints that control how it moves. One of these joints is the elbow joint, which is one of the most used joints due to how important our hands are to our everyday lives. Building a model of an elbow joint can help you and others see how this joint works.
The materials you'll need depend on how complex you want your model to be. If you simply want a small workable model that doesn't emulate the look of an arm, use craft sticks to function as arm bones. If you want a more realistic look, use plastic bones.
The same is true of tendons. Simple rubber bands will do in the case of a craft-stick model, but they would look somewhat cheap in a model using plastic bones. Find heavy-duty pieces of rubber, and paint them white to match the colour of tendons. They should be strong enough to offer resistance when you pull your joint, but not too much that it causes your model to collapse. You will also need something to tie the craft sticks or bones together.
For the craft stick model, use a simple black hair tie, while the bone model should definitely use thick pieces of rubber. Finding a good medium may take experimentation.
The following description for making an elbow model calls for craft sticks. If you're making a more realistic model, replace the craft sticks with bones and the rubber bands with heavy-duty rubber.
Lay one stick down horizontally, and place the other stick vertically on top. This should form a reverse L, with the lower stick to the left instead of the right. Wrap your black hair tie around your sticks several times to hold them in place and create your elbow joint. The tie should be firm enough to keep the angle, but have enough give to allow the sticks to move.
Use scissors to cut one groove at the top of each side of your upper stick. The grooves should slant downward to hold the rubber band in place. The groove on the left side of the stick should be 3 mm (1/8 inch) from the top. The groove on the right should be down about 3 mm (1/8 inch down from the groove on the left side.
The first groove on the lower stick should be on the right tip. It should slant downward. The other groove should be about 3 mm (1/8 inch to the left of the upper stick and should slant down and to the right.
Stretch a rubber band from the left groove on the top stick to the left groove on the bottom. Push it down into each groove until it is snug. Adjust it to keep the band tight between the grooves. Stretch another between the right groove on the top and right groove on the left. Adjust this one to keep it tight as well.
Move the elbow and see the way the tendons tense when you move the arm. Watch the way the joint--where you've tied the sticks together--reacts to the movement.