Changes in apparent leg length (LL) (leg  retraction) have been used by many as a means of locating subluxation in  various joints. The leg check is based on the assumption that unequal  muscular contraction (e.g. hyper irritable muscles) about the spine and  pelvis have the ability to retract one leg relative to the other.  Despite claims of usefulness, many problems are inherent in the prone  leg check such as: a) measurement error; b) subject positioning by the  examiner (expectancy bias); c) interference with the surface of the  examination table; d) possible overwhelming effects of large muscles  over smaller intersegmental muscles and; e) lack of information of the  validity of subluxation (eg. segmental aberration) and it’s supposed  neurological effects. While observation of leg retraction has not yet been  correlated with patient outcome or health measures, it is implied that  the phenomenon apparent changes in LL occur due to altered tonic neck  and back reflexes which coordinate spinal movements and posture. A video  recording has been made of a patient who exhibited an unusually large  amount of leg retraction which appeared to be due to asymmetrical  contraction of their supra-pelvic musculature upon maneuvers such as  tucking their chin.


The purpose of this study is to quantify  the involuntary movements which nave been observed about the spine,  pelvis and extremities using a 2D motion analysis system.


A subject exhibiting a large involuntary leg  retraction will be sought. The patient will be positioned prone on an  adjusting table. Retro reflective markers will be placed about their  spine, pelvis and extremities. The markers will be recorded by two video  cameras during maneuvers which cause the leg to retract.


This data will yield 2D maker locations which will be used to quantify the amount and type of movement.


Despite claims of utility of the prone leg  check to locate subluxation and treatment success, many confounders  occur. Lack of objective documentation and theoretical basis of the leg  retraction phenomena has hindered its acceptance as an examination  procedure. Only indirect evidence exists for its validity in several  small observational studies where it was used to determine were to  adjust. Motion analysis, and EMG studies may help in understanding the  physiology of this phenomena using. Further work is necessary to  correlate the relationship of leg retraction to other methods of  subluxation assessment, treatment outcome and patient health status, if  any.

Reference: Paul J. Osterbauer,DC; Arlan W. Fuhr,DC. Proceedings of the California Chiropractic Foundation’s 7th Annual  Conference on Research and Education, June 19-21,1992; pp.291-292.