‘I have to lift my leg into the car”. This is a pretty common complaint and we hear it a couple of times in a week.
Ben Tolson, one of our acupuncturists and a Sports and Deep Tissue Massage therapists was tackling one of these recently. We’ve had a good discussion about it over coffee in the clinic. And so, this blog.
We came to the conclusion that the classic, and often misdiagnosed, problem is a low-grade mechanical back pain as a result of a twisted pelvis.
Why should this hurt and so you lifting your leg?
Well, the answer here is in your anatomy. The main muscle that you use to lift your leg is called the iliopsoas muscle. This muscle originates along the edges of all your lumbar vertebrae and inserts on the top of your femur. You use it to bend at the hip and lift your leg into the car. The muscle has to contract in order to pull the femur bone closer to the body. An unfortunate side effect of this is that it also causes all the vertebral bodies in the lumbar spine to be compressed. This compression will hurt your low-back.
The world guru on this is a bloke called Professor Stuart McGill. He writes that the compression caused by carrying out a traditional sit-up “..imposes approximately 3300 N (730 lbs) of compression on the spine”. He adds that a bent leg raise – so, the action you do to get into your car, imposes 1767 N of compression. If your low-back is irritated, then this compression will cause your low-back joints to howl. Your brain will then prevent you from even trying to carrying out the move. You will not want to lift your leg in and out of the car. What you are doing to prevent this is to not use this muscle but lift your leg in and out by hand.
Prof McGill adds that the National Institute of Occupational Safety and Health set the limit for low-back compression in workers at 3300 N. So, it certainly makes sense to never do a sit-up again. And now you know why your low-back hurts. You also know why you have to lift it in and out of the car (and I bet it is pain free when you do this as your iliopsoas muscle is not being used at all).
However, there are a few other nasty reasons you can’t lift your leg into a car. Pleasingly, these are rare and pretty easy to diagnose once you know what you are thinking about. They are:
- Where you injure your iliopsoas muscle and it calcifies at the muscle to tendon junction and, as it passes over the pelvic rim, it will sting.
- You tear in the cartilaginous edge of the hip. Thius is a labral tear and should be pretty obvious if checked correctly.
- You can have a Sartorius muscle injury or a groin strain, and, again, this should be pretty easy to diagnose if you think about it first.
- Arthritic changes can also cause the same problem but you should also know about these.