Understanding Limb Length Discrepancy (LLD)

Causes, Effects & Treatment Options

What is a limb discrepancy?

The long and short of it (no pun intended) is that one limb such as your arm or your leg is shorter than the other arm or leg. This might not seem like a big deal and most of the time it isn’t, but it can be something that predisposes further biomechanical complications that can lead to injury or dysfunction.

Now, everyone has a leg or an arm that is shorter than the other. It Is reported that 90% of school children have a limb length discrepancy (LLD). Nearly 50% of athletes are also thought to have a LLD. We are not symmetrical. We are humans and symmetry in the human body does not exist, but how much does it have to be different to care?

When discussing an LLD, we are normally concerning the legs, as that has more of an impact on biomechanics due to walking on both legs thanks to evolution. This is where the change in height of one leg can cause a tensegrity issue traveling through and up the tissues (ligaments, tendons, muscles, cartilage, bone etc.) of the lower limbs. This, in turn, can start to put excessive strain through these tissues leading to a functional adaptation or pain. When pain or dysfunction is present this is when concern takes place to help resolve the discrepancy leading to it.

When assessing an LLD, it can become complicated due to different types. A functional LLD can be down to the body adaption, due to demand of a sport or lifestyle causing muscle contracture. This is normally seen around the pelvis and known as a tilt. Where as a structural LLD is a result from bone formation and the growth becoming impeded, sometimes due to surgical intervention, fractures, infection or growth plate complications. The Tibia or the femur on one side is shorter as a result.

So when do you really need to address the issue? Well that depends on how its effecting the person. If a patient had a LLD and is functionally sound for their sport or lifestyle and is not in and discomfort or disfunction then why would you want to change and adapt that? If you do then it could alter how the patient feels or performs and cause further complications. On the other hand if a patient is feeling discomfort and/or dysfunction, and we decide its highly likely due to the LLD, that is when further testing and interventions would be advised.

When a child has a LLD to a sufficient degree that it could alter their growth and biomechanics while they are developing even without any pain it would still be advised to find the cause and treat accordingly to reduce that risk later in life. In most cases a simple orthotic can do the trick to raise the shorter leg but in others it could be a case of exercises and or bracing if its to correct a scoliotic curvature and muscle imbalances.

Biomechanical screening can be a big help to search for issues with stability, mobility or endurance of tissues. Gait assessment is a very useful tool when it comes to this type of issue as most people walk a lot during an average day, and the demand of so many tissues and joints during the gait cycle is worth considering, let alone when you add specific exercises or other demands like a LLD into this.

This is where a exercise rehab and treatment plan tailored to a LLD is massively important and a very useful tool and not only can help short term but long term too.