Knee Joint Laxity and Neuromuscular Characteristics of Male and Female Soccer and Basketball Players

Abstract & commentary

Synopsis: Decreased joint proprioception could render knees less sensitive to forces and hence at greater risk for ligament injury.

Source: Rozzi SL, et al. Knee joint laxity and neuromuscular characteristics of male and female soccer and basketball players. Am J Sports Med 1999;27(3):312-319.

In an effort to further explore the role of joint proprioception and muscle activity in knee joint stability, Rozzi and colleagues compared knee joint laxity, joint proprioception, lower extremity balance, the amount of time required to generate peak torque of the knee flexor and extensor muscles, and electromyographic (EMG) assessed muscle activity in 17 male and 17 female healthy college athletes. Knee joint laxity was quantified by using a KT-1000 instrumented knee arthrometer to measure anterior tibial translation during application of a 30-pound anterior displacement force and with the subjects tested in the supine position. Using a device specifically designed at the University of Pittsburgh, proprioception was measured by testing threshold to detection passive motion with the subjects seated. The Biodex stabilizing system was used to assess balance and time to generate peak torque of the knee joint flexors and extensors.

Surface electrodes were used to obtain EMG data on each muscle with the data processed and analyzed by Myoresearch software to determine onset time, amplitude, and area of contraction subsequent to landing.

Rozzi et al found that the women tested had greater knee joint laxity, demonstrated a significantly longer time to detect the knee joint moving into extension, possessed superior single-legged balance, and produced greater EMG peak amplitude and area of the lateral hamstring muscles subsequent to landing after a jump than did the males who were tested. They theorized that the decreased joint proprioception could render the knee less sensitive to forces and hence at greater risk for ligament injury.

Comment by Letha Y. Griffin, MD, PhD

This article is another excellent addition by the Pittsburgh group to the ever-increasing pool of knowledge concerning neuromuscular influences on knee joint injury and, in particular, as a risk factor for anterior cruciate ligament (ACL) injuries. Women, compared with men, have been found to have a two to eight time increase in ACL injury rates in pivotal sports such as soccer, volleyball, and basketball. However, the cause for this increase in injury rate is not well understood. Approximately 70% of all ACL injuries occur from noncontact mechanisms. Reported risk factors for injury include environmental factors (braces, shoe surface interface, etc.), anatomic factors, hormonal factors, and biomechanical (neuromuscular) factors.

A recent consensus conference on prevention strategies for noncontact ACL injuries held in Hunt Valley, Maryland (June 1999), examined available data on these risk factors and concluded that at the present time neuromuscular factors appear to be the most important reason for the differing ACL injury rates between males and females.

Although the neuromuscular risk factors for injury have not been fully defined, as illustrated by this article, several prevention programs based on altering neuromuscular risk factors have been developed.1-4 Early data on initial trials of these programs demonstrate impressive decreases in injury rates. Hence, the Hunt Valley conference attendees felt that until specific predictive and protective factors for noncontact ACL injuries are definitively determined, enhanced awareness and continued implementation of these existing neuromuscular preventive programs were reasonable. However, the attendees stressed the need for continued assessment and improvement of such programs.


1. Caraffa A, et al. Prevention of anterior cruciate ligament injuries in soccer. A prospective controlled study of proprioceptive training. Knee Surg Sports Traumatol Arthrosc 1996;4(1):19-21.

2. Griffis ND, et al. Injury prevention of the anterior cruciate ligament, abstract #13. Presented at the annual meeting of the American Orthopaedic Society for Sports Medicine, Traverse City, MI, 1989.

3. Hewett TE, et al. Plyometric training in female athletes. Am J Sports Med 1996;24(6):765-773.

4. Ettlinger CF, et al. A method to help reduce the risk of serious knee sprains incurred in alpine skiing. Am J Sports Med 1995;23(5):531-537.