Excerpted from:  (Page, Frank, Lardner.  Assessment and Treatment of Muscle Imbalance, The Janda Approach.  2010, Human Kinetics, Champagne IL.)

According to Janda, the traditional approach to chronic musculoskeletal pain taken by clinicians has been a purely orthopedic (structural) approach that relies on their knowledge of anatomy and biomechanics. However, functional pathology of the motor system describes impaired function of structures rather than damage to structures.

The functional approach recognizes unseen mechanisms related to the function of the neuromuscular system.  Muscle imbalance is an example of functional pathology in which opposing muscle groups are imbalanced in length or strength, creating abnormal joint function.

There are several muscle imbalance paradigms, most notably biomechanical and neurological perspectives, each with clear evidence. Vladimir Janda was a pioneer in neurological muscle imbalance leading to chronic musculoskeletal pain.  He suggested that the function of the central nervous system (CNS) as opposed to the structure of the muscular system plays the key role in chronic pain pathogenesis and maintenence.