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Pull your socks up! Can you build a pair of legs to demonstrate the power of the patella? Join Dr Chris and Dr Xand and take on The Kneecap Challenge!

Step 1: Tape the rulers back to back, then unfold them and tape along the inside fold (see the clip above). They will be the bones of your legs and the tape is the ligaments holding them together at the knee joint. You should have two flexible knee joints with all four rulers.

Step 2: Next, create the feet by stuffing paper into your socks.

Step 3: Attach each sock to both ruler legs by inserting the ruler into the sock and tying it with string tightly.

Step 4: Cut the legs off the tights. Get a grown-up to help.

Step 5: Tie each leg from the tights to each sock string, this acts as a tendon.

Step 6: Take your cylinder and tape it just below the knee bend on one of the ruler legs. This forms the patella for this experiment.

Step 7: Dangle both ruler legs over the top of a counter or a chair, with the stretchy tights pulled up the top of the ruler leg.

Step 8: Try to pull the tights gently and make the foot rise up on each leg.

Did you notice it was much harder to pull the tights tendon without a cylinder acting as a patella? 

Watch the whole episode of Operation Ouch! Do Try This At Home: The Kneecap Challenge on ´óÏó´«Ã½ iPlayer.