Leg length differences and the effect on cycling comfort has always been a fascination of mine. It led me to start a university degree in Osteopathic Medicine.
Its fair to say that most of us have a leg length difference, that in normal life wouldn’t cause any serious issue. Similarly but entirely unrelated, most adults would show signs of disc degeneration in our spine. Having one, either or both show up on a scan may be entirely relevant or irrelevant depending on the answer to one really obvious question.“Is there a presentation of PAIN or DISCOMFORT?”
When there is a combination of pains and discomfort (not limited to) one sided lower back pain, one sided saddle sores, one sided neck pain, knees tracking both in the same direction i.e. to the right, and many other issues, I would begin investigating a leg length difference. This is part of the interrogation process/interview at the start of any appointment, where the quality of the answers I get from my client leads to a clearer diagnostic process moving forward.
“IF you are pain free, I can not make you more pain free”
Because a bike is such a rigid construct, the body must conform to the placement of the bottom and top of pedal stroke, and it is the same on each side of the bike. When the body on top of it is not straight, the body must confirm to the best of its ability to reach these rigid placements. Pain and discomfort are often the result of this adaptation. This isnt the same when walking, because you can reduct your stride and alter yourself to be in a more uniform movement from the bodies perspective.
To measure a leg length difference, there are a number of methods with a variety of different results. The most accurate (and the only way I put an adaptation in nowdays) is called an EOS Scan. I encourage you to follow the link to the EOS scan to understand a bit more about it. On the spot, I prefer to measure the PSIS manually, and will get my client to bend to their cycling position while I feel for movement and change. Testing usually includes adding something underneath one foot, and repeating until the PSIS measure the same left to right, and the pelvis isnt skewing when in a bent position.
Other practitioners will use a method that is non-weight bearing, which in my opinion does not reflect appropriatley what we are trying to measure. An EOS scan however is weight bearing, and SUPER accurate.
On more than one occasion a client has been told they have a Leg Length Difference (LLD) to have it confirmed as the opposite leg to that originally claimed. EOS scans when relevant to lower back pain can attract a medicare rebate, but this is a conversation you need to have with your referring professional such as physio, GP or Specialist.The solution is actually very simple, once we know what the LLD is. I prefer to use 3d printed Shims that go between the shoe and the cleat, but there are some off the shelf options available as well.
Once installed, it can take between minutes and months for a correction to be felt. Sometimes people take them out, or dont carry their shim across to their new shoes, and only months into the new shoes do the original symptoms return. Its not an easy task to encourage a body to realign itself, especially when there is normally some uneven saddle bending/wear as well. This is why I will often ask clients to replace saddles as well as install a shim simultaneously.
Its a topic I could discuss for thousands of words, but as a breif overview, this is a good start.
