Maja, 36, has recovered from her runner's knee and is back into running training. A few months pass without injuries, she increases her training load. In a week's next half marathon is on. As it pulls and hurts it all at once in her left buttock. "Is that the sore muscles of my Intervallläufen?", Maya asks.

But the next day, there are strong back pain, radiating to the leg. Like a knife piercing the lower back, gnawing. Getting up from the sofa or bowing down to the children will soon be impossible. Maja is worried: "Did I fall and do not remember? Is this a herniated disc?"

Maja tries pain medication, heat and cold therapy. But the pain does not really want to disappear. "In the cross put on many muscles that are very important for the mobility of upper body and legs," says Pouria Taheri, orthopedist in Berlin. "When you have a back pain, there are so many aspects to it, and the pain is usually nonspecific in the back and legs." A herniated disc was possible, but not the most likely cause. Therefore, a detailed clinical examination is important in conjunction with a recent MRI image of the lumbar spine.

Where does the pain in the cross come from?

A probable possibility: a block in the sacroiliac joint, short ISG. The ISG is the transition from the sacrum to the ilium. "For being referred to as a joint," says Taheri, "there is very little room for maneuver." But that makes perfect sense: The joint keeps the transition of the lumbar spine into the pelvis stable, strong ligaments around the ISG direct the power from the upper to the lower body.

In the region of the ISG, many muscles, such as the large gluteal muscles, stabilize the joint. "But if you walk a lot, run long, raise or are overweight, you may experience overload, tension and a muscular imbalance," said sports doctor Taheri. This then leads to a small but significant malposition of the joint. This results in an inflammatory process around the joint - even through everyday movements. The result: pain in the cross.

A sports doctor then recommends mostly physiotherapy. Through manual treatment, the therapist attempts to restore mobility and original joint position to restore muscle tone and tension to the short muscles around the cross. That does not work with one hand, but takes time. You should definitely take a break from exercise until the pain is gone, otherwise the injury will only get worse.

Low back pain due to stress

Emotional stress can also be the cause of low back pain. "It's not always just physical changes that make themselves felt in the cross," says Taheri, "and stress at work, quarrels with the family and generally emotional discomfort can be triggers." The sports doctor is convinced that often even a stress-reduced lifestyle and less pressure can change the pain.

The lifestyle of the average German - sitting a lot, working on a computer and staring at the phone with his back to his or her spine - is, however, characterized by too little movement. This too can trigger pain in the cross. "We do not stretch our muscles too much during the day and do not relieve the skeleton," says Taheri.

Build stretching exercises and muscles

Wherever the pain in the cross comes from: To mobilize and stretch the muscles, and especially the gluteal and back muscles to strong with body-stabilizing exercises is the alpha and omega.

When the pain is already there, different stretching exercises help for the back. For example, while standing, bend the upper body forward and try to touch the ground with your hands, legs remain stretched. As a precaution, so that the back pain does not come back so quickly: Planks with movement (eg knee to the elbow pull) and other stabilization exercises in the training plan install.