Muscles are active components of the locomotor system, controlled by neural impulses. Approximately 40% of human body tissues consist of striated skeletal muscle, whose contractions are driven by signals from the nervous system. Skeletal muscles may reach lengths of up to 50 cm and work in close cooperation with auxiliary structures such as fascia, bursae, tendon sheaths, sesamoid bones, retinacula, and fibro-cartilaginous pulleys. These tissues are clinically important, as palpation often reveals valuable diagnostic information.
The spine plays a crucial role in transmitting neural information to various parts of the body, protecting the spinal cord while — in cases of dysfunction — potentially contributing to nerve irritation. Disrupted neural communication between the central nervous system and peripheral structures may influence motor control, muscle tone, pain perception, and overall function.
Muscles as Contributors to Static Pelvic Imbalance
Static muscular imbalance (SMI) is frequently associated with dysfunction of the pelvic girdle. Altered muscle tone, strength asymmetry, or impaired coordination around the pelvis may generate symptoms that radiate to distant body regions. Postural muscles and spinal curvatures adapt to gravitational forces through compensatory strategies. Because the spine is functionally dependent on the sacrum — and the sacrum is supported by the ilia — muscular forces acting on these structures significantly affect overall static alignment.
Contemporary research highlights that SMI is not only a structural phenomenon but also involves:
- impaired neuromuscular control,
- altered proprioception,
- changes in fascial tension,
- maladaptive movement habits,
- and central pain modulation mechanisms.
Therefore, assessment should include both local biomechanics and global movement patterns, as well as psychosocial influences on pain.
Muscle Groups Commonly Associated With SMI-Related Pain
- Iliopsoas
- Tensor fasciae latae
- Biceps femoris
- Rectus femoris
- Lumbar paraspinal muscles
- Deep spinal stabilizers and superficial back muscles
Mixed SMI patterns are common — for example, simultaneous tightness of flexors and extensors within the same joint, creating complex compensations.
Potential Consequences of Muscular Imbalance
- Apparent leg-length discrepancy
- True leg-length discrepancy (less frequent, requires careful differential diagnosis)
- Hyperlordosis
- Altered sagittal curvature (dyslordosis)
- Scoliosis or scoliotic posture (often functional rather than structural)
Clinical Implications and Current Therapeutic Approach
Modern management emphasizes comprehensive, individualized assessment including:
- evaluation of strength, endurance, and muscle length,
- pelvic and spinal biomechanics in motion (not only in static posture),
- neuromuscular control and coordination,
- gait and functional tasks,
- pain mechanisms and patient-reported outcomes.
Evidence-based interventions may include:
- targeted strengthening and mobility training,
- motor control and stabilization exercises,
- soft-tissue and myofascial techniques when indicated,
- gradual load progression,
- ergonomic and movement education,
- addressing lifestyle, sleep, stress, and physical activity levels.
Importantly, therapy aims not merely to “correct posture,” but to restore efficient, pain-free movement and build tolerance to everyday loads.