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Your body is not symmetrical. So what?
- Yannick Sarton
- May 4
- 4 min read
The idea that the human body should be perfectly symmetrical is widely shared, both on social media and sometimes in clinical discussions. However, when we look at recent scientific literature, the relationship between structural asymmetry and pain is not clearly established.
Many postural and biomechanical findings show poor correlation with symptoms. In other words, identifying an asymmetry does not necessarily mean identifying the cause of pain.
Understanding this helps avoid unnecessary concern and keeps the focus on evidence-based management.
The myth of leg length discrepancy
Leg length discrepancy is frequently presented as a major source of asymmetry.
Current evidence suggests that small differences in leg length are very common and generally not associated with pain or functional limitation. Differences below approximately 20 mm are typically considered clinically insignificant in most individuals (1,2).
Is 20 mm a lot? Yes, it is substantial. Most people are well below this threshold.
Another key point is measurement. Clinical examination alone is not sufficiently reliable to accurately assess leg length discrepancy. More precise methods, such as imaging techniques, are required for valid measurement (3).
For patients, the message is simple. A slight difference in leg length is common, and based on current evidence, it is very unlikely to be the primary cause of your pain.
The myth of pelvic tilt
Pelvic tilt is often used to explain low back pain. The reasoning is intuitive but not strongly supported by current evidence.
Most cases of low back pain are classified as non-specific, meaning that no single anatomical structure can be clearly identified as the source of symptoms (4,5).
When we focus on the sacroiliac joint, frequently described as “misaligned,” its actual movement is extremely limited, typically around 2 to 3 degrees. This does not support the idea of large positional faults driving symptoms.
It is important to be careful with how this information is communicated. Describing the body as “misaligned” may lead patients to believe that something is structurally wrong, which can increase concern and negatively influence recovery.
Current research consistently supports a multifactorial model of low back pain, involving physical, psychological, and contextual factors rather than a single biomechanical cause (4,5,6).
Anatomic possibilism
The concept of anatomic possibilism suggests that different regions of the body can influence each other.
From a clinical perspective, this is partly valid. For example, reduced hip mobility may influence lumbar loading, and the relationship between the cervical spine, thoracic spine, and shoulder complex is well recognized.
However, caution is required when extending this reasoning too far.
Some models describe long chains of causality, such as the foot influencing the knee, then the pelvis, then the spine, and eventually the cervical region and headaches. While these explanations can appear coherent, their scientific support is limited.
Modern clinical practice tends to focus on plausible and evidence-supported relationships rather than complex global chains that are difficult to validate.
It is also important to consider how information is delivered to patients. Overly complex explanations can lead to overthinking and increased concern, which are known to influence pain perception and recovery (7).
Clear and simple explanations are often more effective and better aligned with current pain science.
Traumatic pain and tissue sensitization
Musculoskeletal pain can occur with or without a clear traumatic event.
In some cases, pain is related to mechanical loading or tissue irritation. In others, particularly when symptoms persist over time, there is an increasing role of nervous system sensitization.
Chronic pain is rarely explained by biomechanics alone. When pain persists, changes in the nervous system, often described as central sensitization or nociplastic pain, play a significant role (8,9).
In addition, early management of an injury is critical. Inadequate load management or incomplete recovery of movement capacity can contribute to long-term symptoms.
When pain has been present for many years, it is no longer purely a structural issue. It reflects a combination of tissue history, movement patterns, and neurophysiological adaptation.
Conclusion
If you want to manage musculoskeletal pain effectively, it is essential to rely on evidence-based medicine.
There are thousands of researchers working on these topics, across different joints, conditions, and stages of recovery. This work provides a consistent and evolving foundation for clinical practice.
As a physiotherapist, my role is to translate this knowledge into clear and practical guidance.
You are not alone. Chronic pain affects a significant proportion of the global population. Current estimates suggest that around 20 percent of adults experience chronic pain, although this includes all types of chronic conditions, not only musculoskeletal disorders (10).
Within the healthcare system, physiotherapy plays a central role in helping patients improve function, reduce pain, and return to meaningful activities.
The goal is not to achieve a perfectly symmetrical body.
The goal is to build a system that is strong, adaptable, and capable.
I provide structured and evidence-based online physiotherapy for patients worldwide, offering clinical assessment, diagnosis, and personalised rehabilitation.
I also receive patients in person at my physiotherapy clinic in Phnom Penh.
You can begin your online physiotherapy session through the dedicated platform:
More information on clinical standards and supporting evidence is available here:
Yannick Sarton, MSc Physiotherapist
International Online Physiotherapy & In-Clinic Care, Phnom Penh
References
Gordon JE et al. Leg length discrepancy: clinical implications and management. J Am Acad Orthop Surg. 2021
Brady RJ et al. Leg length inequality and musculoskeletal outcomes. J Orthop Sports Phys Ther. 2022
Sabharwal S. Assessment of leg length discrepancy. Orthop Clin North Am. 2020
Maher C et al. Low back pain. Lancet. Updated review 2020
Hartvigsen J et al. What low back pain is and why we need to pay attention. Lancet Rheumatology. 2021 updates
Caneiro JP et al. Beliefs and low back pain. J Orthop Sports Phys Ther. 2020
O’Sullivan P et al. Cognitive functional therapy and pain beliefs. Br J Sports Med. 2020
Fitzcharles MA et al. Nociplastic pain: clinical concept. Lancet Rheumatology. 2021
Kosek E et al. Chronic pain and central sensitization. Lancet. 2021
Mills SEE et al. Chronic pain epidemiology review. Pain Reports. 2020
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