The effect of exercise on anterior-posterior knee laxity

Abstract

A commercial knee laxity testing device was used to quantitate anterior and posterior laxity before and after exercise. Measurements were made at 20 degrees of knee flexion and with a displacement force of 133 N (30 pounds). In sedentary controls no significant change in laxity was noted over 2 hours. Squat power lifters sustained no significant change in laxity after a series of squats (0.4 to 0.7 cm) using 1.6 times body weight. However, 18% to 20% increases in mean anterior and posterior laxity were noted in college basketball players after 90 minutes of practice and in recreational runners after a 10 km race. The role of muscle relaxation in such tests was also evaluated by measuring laxity in normal knees before and during general anesthesia. Negligible laxity change was noted. Thus, functionally "complete" muscle relaxation can be obtained during testing in the cooperative individual. In conclusion, basketball players and distance runners experienced a transient increase in anterior and posterior laxity during exercise. Power lifters doing squats did not demonstrate a significant change in laxity. It appears that repetitive physiologic stresses at a high strain rate produce significant ligamentous laxity, while a relatively few large stresses at a low strain rate do not.

Anterior laxity and MR signals of the knee after exercise: A comparison of 9 normal knees and 6 anterior cruciate ligament reconstructed knees

“…We found a significant increase in anterior laxity in normal knees after exercise, supporting the results of previous studies (Stoller et al 1983, Skinner et al 1986, Steiner et al 1986). The effects of exercise on knees with ACL grafts demonstrated that the change in the anterior laxity of the reconstructed knees was similar to that in normal knees.…”

“…Our findings suggest that the ACL grafts are biomechanically and biochemically different from normal ACLs, even 15 months after ACL reconstruction. An increase in knee joint laxity after exercise haxDbeen reported by some investigators (Stoller et al 1983, Skinner et al 1986, Steiner et al 1986). This phenomenon was thought to be caused by decreased resting muscle tone due to fatigue, the viscoelastic behavior of the ligaments and other structures surrounding the knee joint, or by an elevation in temperature (Woo et al 1987, Fukubayashi et al 1991.…”

Anterior-posterior knee laxity increased by exercise: Quantitative evaluation of physiologic changes

“…Stoller et al (1983) reported that torsional knee laxity, with 10-Nm internal and external torque to the tibia, increased by 14% after 30 minutes of running and that it returned to the level before exercise 52 minutes after running. Steiner et al (1986) reported that, in sedentary controls who were mainly sitting, no change in laxity was noted over 2 hours. Squat power lifters showed no change in laxity.…”

“…Moreover, the threshold of exercise that causes the maximum change is low. Acute changes in knee laxity after exercise have been reported by several investigators (Weisman et al 1980, Stoller et al 1983, Skinner et al 1986, Steiner et al 1986, Johannsen et al 1989, Sakai et al 1992. The knee joint is considered to have viscoelastic properties during exercise.…”

Effects of a 2-Hour Cheerleading Practice on Dynamic Postural Stability, Knee Laxity, and Hamstring Extensibility

“…There are reports of increased laxity in normal knees after activities such as running to fatigue:%gility running (23%) ,z6 distance running (20%) ," cycling (21%) ,I2 and basketball (19%) . 35 Pintsaar et a1 suggested that the medial-lateral (frontal plane) component of dynamic postural stability during unilateral stance resembled the adjustments that occur during the unilateral support phases of walking or running. 24 When the ankle and subtalar joints are adequately controlled by neuromuscular forces, they can more efficiently perform effective postural corrections.…”