Summarize:

A herniated disc (also known as a ruptured disc, slipped disc, pinched nerve, and other names) is a type of injury that happens when one of the fluid-filled discs between the vertebrae of the back breaks, spilling fluid into the surrounding area which can cause painful inflammation and nerve pain. Generally, herniated disc injuries fall into one of two categories, so, to start, pick which one of these you want to fake:   Pinched nerve: The actual disc itself (usually in the lower back) may or may not experience pain and inflammation. In addition to this, shooting pain called sciatica will occur in one or both of the legs or from the neck down the arm.  Local Disc Pain: In this injury, just the area around the disc itself experiences pain and inflammation. The rest of this section will focus mostly on faking a pinched nerve injury because it's a little harder to do. To fake local disc pain, you'll want to act like your lower back is painfully sore and stiff (like a bruise) and that bending, twisting, or carrying heavy weights causes you intense pain. One of the "textbook" symptoms of nerve pain from a herniated disc is the appearance of sudden, intense pains in one or more of the limbs after the injury. This is caused by the fluid from the broken disc pressing on the base of the nerve and creating the sensation of pain even though the limb is not actually injured. Most commonly, a herniated disc will cause these shooting pains in one or both legs, though they can also sometimes lead to pains between the neck and arm.   Leg pain is usually most intense in the buttocks or hamstring, though it can also occur in the calf or foot. Arm pain can be centered in the neck, shoulder, elbow, hand, or the arm itself. In either case, the pain can be so bad that it causes you to grunt or wince and stop what you're doing, even if you're used to it. The pain usually occurs when performing an activity that puts stress on the lower back, not the limb itself. These include: Standing up or sitting down. Leaning back Bending or twisting Carrying something heavy Straightening one leg in front of you (because this tightens the lower back and hip muscles, not because it uses the leg muscles) Another symptom of herniated disc injuries that's indicative of nerve pain is a distracting "pins-and-needles" feeling which is almost exactly like what you'd get if one of your limbs fell asleep. This feeling can be accompanied by numbness, but it can also occur without removing the feeling from the affected area. Usually, this feeling occurs in the same spots as the nerve pain from the injury. The tingling feeling is not usually outright painful, so you don't need to "sell" it especially hard. However, you may want to make a point to mention it to add believability to your act. You can also pretend that using the affected limb while you have this tingling feeling gives you an oddly ticklish, numb feeling (again, just like if the limb had fallen asleep.) Nerve damage from a disc injury can cause the same muscles that are experiencing shooting pains to rapidly become weaker and less flexible than before, even if they don't look any different externally right away. These changes can even affect your posture and gait, especially when the pains are occurring in a leg. Sometimes, these problems are accompanied by twitching.  For example, if you're faking leg pains from a disc injury, you might show the affects on our muscles like this: Having a limping, lopsided gait that keeps the affected leg stiffer than normal. This should be especially bad right after doing something to aggravate the injury (bending, twisting, standing up, etc.) Being unable to raise and straighten the affected leg very far in front of the body without pain and tightness (note that this is one of the clinical tests doctors will perform for this sort of injury)  Being unable to perform activities that require leg strength without pain, like running, kicking, and especially high-impact activities like jumping. Most herniated discs occur in the lower back, so the injuries that cause them are usually from activities that put excessive stress on the muscles and structures there. Some herniated discs occur from a single, definite injury, while others develop over time from bad posture or aging. Below are a few activities known to cause disc injuries that you may want to work into your story:  Sharply bending or twisting, especially when holding a heavy weight Stressing the lower back by leaning back or forward with bad posture, especially when holding a heavy weight Using back muscles (rather than leg muscles) to pick up heavy things. Age-related wear and tear Rarely, receiving a sudden blow to the back or falling Most medical agencies recommend that herniated discs that cause nerve pain should be examined by a doctor. While you should not fake your symptoms to a doctor (as this is a gross waste of his or her time and expertise), you may want to pretend to be thinking of seeing a doctor to enhance your illusion. The pain from disc herniation can be lessened with anti-inflammatory treatments like ice packs, warm compresses, ibuprofen, and so on. However, these things alone will not make a disc herniation better — just temporarily decrease the pain. While most people with herniated discs eventually get better within six weeks, sometimes, more powerful pain medications and even surgery can be necessary.
Decide whether or not to fake nerve pain. Fake shooting pains in your lower body or arm. Pretend to experience numbness and/or tingling. Act like the affected limbs have become stiff and weak. Have a convincing story ready. Pretend to be seeking treatment.