Document Title: Ageberg-AJSM-Oct05.shtml
Article Title: Balance in Single-Limb Stance in Patients With Anterior Cruciate Ligament Injury -- Relation to Knee Laxity, Proprioception, Muscle Strength, and Subjective Function
Authors: Eva Ageberg, RPT, PhD, David Roberts, MD, PhD, Eva Holmström, RPT, PhD and Thomas Fridén, MD, PhD
Publication: American Journal of Sports Medicine, Baltimore, Maryland
Date: October 2005
Volume 33, pages 1527-1535
Keywords: Proprioception, neuromuscular control, knee laxity, isokinetic, muscle strength, subjective functioning, anterior cruciate ligament, ACL deficiency, postural control, joint instability, intrinsic instability, inherent instability, patient satisfaction.

(Reference-denoting numbers appear in the same font and point size as the document text. As with all Knee Library documents, this article is provided in full-text form, complete with all figures and tables.)

Comments: This study looks specifically at the proprioceptive and neuromuscular consequences which flow from ACL deficiency (in particular chronic ACLlessness; note that all the subject in this study had no ACL reconstruction). When a natural ACL is torn, the embedded nerve endings are severed, and so the proprioceptive function (i.e. position-in-space feedback to brain's motor-control center) is lost, as is the protective hamstring reflex. (If the ACL is reconstructed, there is some hope that nerve endings will regrow into the graft, but this takes several years in any case. Moreover, there are still doubts as to whether or not such regrown nerve endings can be expected to become usefully connected to the brain, even in the long term [i.e. over 10 years post-operative].) The authors briefly discuss the proprioceptive role of the ACL, and they note that impaired postural control has been reported in people with chronic ACL tears as well as in people with reconstructed-and-rehabilitated ACL tears. (Note that single-limb stance, hence standing on one leg, is not only a static posture. It is also an integral part of normal walking. This means that the same mechanisms involved in maintaining static posture are also essential to the dynamic process of gait and movement in general.)

ABSTRACT

Background: It has been shown previously that an anterior cruciate ligament injury may affect postural control, measured by balance in single-limb stance. To our knowledge, no studies have reported the influence of measures of impairment on postural control after such an injury.

Purpose: To assess the influence of knee laxity, proprioception, and muscle strength on balance in single-limb stance and to study the correlation between balance in single-limb stance and subjective estimation of extremity function.

Study Design: Cross-sectional study; Level of evidence, 3.

Methods: A total of 36 patients with a unilateral, nonoperated, nonacute anterior cruciate ligament injury were examined with regard to anterior knee laxity, proprioception, muscle strength, and stabilometry (amplitude and average speed of the center of pressure movements). Subjective estimation of extremity function was measured on a visual analog scale.

Results: The multiple regression analysis showed that high knee laxity values were associated with high amplitude values and low average speed. Poor proprioception and high muscle strength values were associated with low average speed among the women only. Low amplitude values correlated with better subjective function.

Conclusion: Anterior knee laxity, proprioception, and muscle strength seem to play a role in maintaining balance in single-limb stance. Patients with low amplitude values in stabilometry were those with better subjective function.

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