If you have thigh pain that sets in when you run and eases up when you rest, it may be tempting to push through the pain. But just because it isn't constant, doesn't mean it's not serious. This pain could be indicative of a femoral stress fracture.

What is a femoral stress fracture?

The thigh bone, also known as the femur, runs from the pelvis down to the knee. When you run, muscles surrounding the femur absorb much of the shock, but these muscles also pull on the bone. If you increase your mileage or speed too quickly, the muscles may put more stress on the bone than it's able to handle. Over time, this added stress can cause a crack in the bone, called a femoral stress fracture.

What are the symptoms?

If you have a femoral stress fracture, you will likely feel a generalized pain throughout your thigh, possibly even down to your knee. As with other types of stress fractures, the pain may only be present during exercise. It will usually feel better after resting, but when you run, it will hurt again. It may also hurt when walking, or when sitting in a chair that puts pressure on the femur. If the injury isn't treated, the pain will continue to get worse.

How is a femoral stress fracture diagnosed?

There are a couple of different tests your doctor may perform to diagnose a femoral stress fracture. One is called the fulcrum test. For this test, you will sit on a chair or table with your legs not touching the ground. Your doctor will place their arm under your thigh, and gently lift your leg. As they're doing this, their other hand is placing pressure on your knee. If you have a femoral stress fracture, at some point during this process, you will feel a sharp pain.

Another common test is the hop test. As you may have guessed, the hop test involves hopping on one leg. This test is considered positive if you feel pain in the injured leg while hopping.

If you receive a positive result from either the hop test or the fulcrum test, your doctor may confirm the diagnosis with an MRI.

What causes it?

Femoral stress fractures are caused by sudden increases in mileage or intensity. Some new runners find themselves sidelined after starting too ambitiously, or diving into a hard training cycle without a proper base. To prevent stress fractures, don't increase your speed or distance more than your body can handle. Some doctors recommend following the ten percent rule, where you increase your mileage by ten percent each week.

How is it treated?

The recovery time for a femoral stress fracture is between 8-16 weeks. During this time, you will be encouraged to rest and engage in activities such as swimming or cycling. Some runners find that pool running is great for maintaining fitness while still allowing their bodies to rest. Usually the femur will heal itself while resting. Your doctor may have you wear a splint, and walk with crutches. It's important to wait for your doctor to give you the green-light before returning to running.

Femoral stress fractures take a long time to heal, but continuing to run on the injury will only make it worse. It's important to take time off to let your body recover before jumping back into training. And also remember to talk to your orthopedic specialist for more information.