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The Hidden Culprit: How Weak Hip Flexors Can Cause Back Pain and Sciatica

*For Informational Purposes Only. Not Medical Advice.

Recently, I was talking with another mom who mentioned that she now has sciatica after having her babies. As someone who experienced sciatica during my first pregnancy, I know how debilitating it can be. Luckily, corrective exercise can help address the root cause of the problem if your sciatica is caused by muscle weakness or imbalances. In addition, your regular old lower back pain can also be alleviated by strengthening the hip flexor muscles (and deep core muscles), so if your doctor says that you are healthy enough to exercise, let’s do it!

Firstly, let’s address a common misconception that back pain or sciatica are always caused by poor posture, heavy lifting, muscle injuries, pregnancy, being overweight, etc. Back pain is a common ailment that affects people of all ages, and often interferes with daily activities and quality of life, but correlation does not equal causation, so all of those things might contribute to your pain, but don’t necessarily explain the root cause. Muscle imbalances are often completely overlooked within the medical model, and unless you have the opportunity to speak with a physical therapist, your cries for help will likely go unanswered. Keep reading to explore the link between weak hip flexors and back pain, how it contributes to the development of sciatica, and how taking action to correct the problem can provide relief and prevent future discomfort.

Understanding the Hip Flexors

The hip flexors are a group of muscles that you use when you lift your knees toward your chest. You need them to walk, run and sit. There is the iliopsoas (the primary) and the rectus femoris (a part of the quadricep) and a few others. When they become weaker, the weakness affects your posture and the alignment of your spine, which, over time, leads to back pain and sciatica.

There are a ton of reasons why the hip flexors can become weaker than they should be, including poor posture, sedentary lifestyle, injuries, nerve impingement, surgeries, etc., but today, I want to specifically talk about how pregnancy, and commonly, back to back pregnancies can really screw with those muscles. I’d also like to mention that zero percent of this information was ever shared with me during all four of my pregnancies, births, and recoveries. I had to learn all of this on my own, so if you’re thinking, “my doctor never said any of this”, believe me, I know.

  1. Hormone Changes: We know that we emit relaxin during pregnancy, that relaxes the ligaments in the pelvis. While relaxin is important to birth a baby, it’s not so great for the stability of our joints, which can affect the hip flexor muscles.

  2. Weight Gain: gaining weight (whether excessive or not) puts stress on the hip flexor muscles, which causes chronic muscle fatigue, and eventually a weakness.

  3. Postural Change: Growing bellies make us adjust our posture, often times tilting the pelvis forward. When we do that, we overuse our lower back muscles and underutilize the hip flexors.

  4. Reduced Physical Activity: any time throughout your life when you are doing less activity, your muscles will atrophy due to lack of use.

  5. Pressure on Nerves: A growing baby puts pressure on nerves, which innervate the hip flexor muscles, causing weakness over time.

  6. Stretching of the Abdominal Muscles: when the core muscles stretch to accommodate a baby, it affects your core stability and indirectly weakens the hip flexors. ***Note: if you’ve done any type of core rehab, or any of my Mommy Strong programs, you might remember me talking about how all of these muscles work together with your glutes to stabilize the whole body. You can’t have a “weakest link” here… they all need to pull their weight for the team.

If you’re still having babies, take this advice: during pregnancy, stay active, do pelvic floor exercises that work your transverse abdominis (deep core), hip flexors and glutes (do not just do kegels, it goes far beyond that), and request a pelvic floor physical therapist consult after birth. You can often get your insurance to pay for this if your doctor puts in a referral during the postpartum period.

If you are done having babies, never fear! We can course correct! Keep reading.

How can a couple of small, weak muscles cause such painful sciatica? I’m glad you ask.

When our hip flexors are weak, we often see an anterior pelvic tilt, where the pelvis tilts forward and the low back arches excessively (think: sticking your booty out). This is an unnatural posture which stresses the lumbar spine. In addition, the muscles surrounding the hip interact with the muscles in the lower back and the transverse abdominis. So when one muscle is weak, it strains the other muscles trying to pull the extra weight. Specifically, when the hip flexors are weak, it strains the low back muscles, which can compress the sciatic nerve. The sciatic nerve runs from the low back down the legs, and can become compressed or irritated due to:

  1. Spinal Misalignment: you can see a chiropractor to assess this.

  2. Muscles Imbalances: you can strengthen these muscles on your own or with the help of a professional.

Most often, the pain is caused by a combination of the two causes. I’ve worked with a lot of moms in my career, and most everyone has some level of weakness in these areas after having babies. Spinal alignment isn’t my area of expertise, so I will recommend that you discuss with a chiropractor in your area.

What can we do about it?

  1. Start with the basics. Take a personal assessment of your hip mobility and range of motion. Evaluate your posture. Write down where you’re at today and start doing some research into where you should be for optimal health. Write down a couple goals with a plan of action and an end date.

  2. Pay attention to your posture more often. Make it a point to keep your pelvis neutral while standing. If you’re used to having an anterior pelvic tilt, this is a hard task. I still default to tilting forward and haven’t mastered it myself yet. I’m almost 5 years out from having my last baby.

  3. Stretch the hip flexors and surrounding muscles regularly. Stretching will help relieve the tension in the area and loosen you up once you start doing strengthening exercises. I like to break the two up throughout the day. Do my strengthening stuff during my regular workout, and thoroughly stretch everything out before bed.

  4. Work on your Core Strength: Dump the idea that situps and crunches are the only way to get a strong core. Those types of exercises target the superficial muscles of the core, and don’t do much for the inner core muscles that actually need the stability. If you’re looking for a free way to find out more information on these types of exercises, go on youtube and search for “diastasis recti exercises” and go nuts.

  5. Start doing 5 minutes of hip flexor exercises each day. If you are a self-directed person, you can utilize Youtube for this as well (isn’t the internet amazing?).

  6. If you do better with a directed program, you can consult with a physical therapist or a personal trainer that specializes in postpartum recovery (like myself) and we can come up with a personalized plan for you.

Bottom line: don’t assume you’re indefinitely stuck suffering in pain. One of the main points that I push with my clients is that “normal isn’t optimal”, and if we can do a little extra work to figure out the true root cause of the problem, we might be able to skip doing the bandaid over a bullet hole charade and solve it completely. It’s amazing what a little extra effort will do, in a country that wants you sick, tired, and in pain.

Talk Soon!


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