Lower Limb Biomechanics Assessment - Why?

As human beings we are ambulatory creatures, that is we walk upright and are very reliant on our legs to move us about. How the foot strikes the ground and the knock on effect this has up the lower limbs to the knee, hips, pelvis and low back in particular has become a subject of much debate and controversy in recent years.

Lower limb biomechanics refers to a complex interplay between the joints, muscles and nervous system which results in a certain patterning of movement, often referred to as ‘alignment’.

Much of the debate centres around what is considered ‘normal’ and what is considered ‘abnormal’ in biomechanical terms as well as the extent to which we should intervene should abnormal findings be found on assessment.

The purpose of a biomechanical assessment is to determine if your pain complaint, for example sore knees while running, has been caused by or not being allowed to heal as a result of a lower limb biomechanical abnormality.

In order to determine this we do an assessment where we first make a diagnosis of the knee pain, for example ‘patellofemoral pain syndrome’ (AKA runners knee).

Related article: Common Running Injuries - How To Treat and Avoid

We would then go on to perform a complete lower limb biomechanical assessment to determine whether the pain is likely to have developed due to abnormal biomechanics of the lower limb while running.

A typical lower limb biomechanics assessment would comprise of the following:

• A posture assessment, the whole body that is, but with emphasis on the waist down. The foot posture index is an assessment tool which may reliably be able to identify and score abnormalities about the foot and ankle.
• A gait assessment - both walking and running
• An assessment can be used to determine the level of external support required to place the foot and ankle in a more ‘normal’ position while standing, walking and running and may provide the basis for an individual orthotics prescription depending on which system is used. Here at the clinic we use the scientifically validated PPL prescription platform method
• Muscle length and flexibility tests
• Tests of muscle strength and control - the more functional the better such as the squat, lunge, hop and jump tests to determine how lower limb alignment is affected by loading and movement.
• Tests of balance and agility such as the use of a balance board, uneven or unstable surfaces and swiss/ gym balls
• Sports specific tests as required

What is normal?

Biomechanical studies over the years have given us a good idea as to what is ‘normal’ or ‘ideal’ in biomechanical alignment terms as such we are able to identify what is abnormal on assessment.

The tricky bit, and which causes much of the debate, is that there are many people out there running for example with very abnormal biomechanical findings on assessment and have absolutely no pain as a result!

As such how can we conclusively deduce that abnormal biomechanics is in some way related to the development of the persons pain complaint?

Value of experience

This is where the experience and training of the physiotherapist becomes important. An experienced physiotherapist who has been trained in biomechanics will start by making small adjustments to the biomechanical function of the lower limb and determine to what extent this may or may not affect the pain symptoms.

If for example the use of a temporary shoe orthotic to restore a more normal subtalar joint alignment to an over-pronating foot results in a significant decrease in knee pain while running, this clinical evidence would allow us to conclude that indeed there was a biomechanical issue at the root of the problem.

Related articles:

• Shoe Insoles - Cure or Curse?
• Running Confusion - Shoes vs Barefoot vs Orthotics

Other adjustments which can influence lower limb biomechanical function include:

• Changes in footwear
• Exercise surfaces
• Clothing
• Taping
• Gluteal and other ‘core’ muscle strength and control
• Muscle length - particularly in the quadriceps, hip flexors, hamstrings and calves
• Balance
• Proprioceptive function and technique

The key is knowing when and how to intervene and in what order. It should be remembered that as with most disciplines within physical medicine, treating biomechanical problems can be a process of trial and error and ongoing assessment and reassessment until the desired end result is achieved; good pain relief and a return to full movement function.