Eva Ageberg, RP7; MS$ Markus W a l d h , M9 Rose Zatferstrom, RP7; P h D Several tests of human conscious knee proprioception have been described, but there is no consensus or reference standard established. Difficulties remain in the separation of information originating from muscles, tendons, and joints, and the tests cannot discriminate between loss of afferent signals or altered activity in the remaining receptors. There is convincing evidence from several descriptive studies that the afferent information is altered after a knee ligament injury and severely disturbed in some patients with anterior cruciate ligament (ACL) injuries. However, an inherent inferior proprioceptive ability may also exist in some individuals, which makes them vulnerable to injuries. The deficits in proprioception have mostly been studied and related to the consciously registered sense, whereas the extent of possible disturbances of the unconscious or reflectory mechanisms is largely unknown. The latter may, at least from a theoretical point of view, be predominantly contributing to the overall afferent regulation, and a possibility for major defects thus exists, since there is no knowledge of the quantified relation between the conscious and unconscious part. The clinical importance of the altered afferent information has not been evaluated properly, and the role of proprioception that contributes to function has yet to be investigated. A higher physiological sensitivity to detecting a passive joint motion closer to full extension has been found both experimentally and clinically, which may protect the joint due to the close proximity to the limit of joint motion. Proprioception has been found to have a relation to subjective knee function, and patients with symptomatic ACL deficiency seem to have larger deficits than asymptomatic individuals. Little is known about whether training can restore defects in sensory information or by which mechanisms possible compensatory pathways are established. In rehabilitation, each patient must, however, create muscle strength, alertness, and stiffness in harmony with the disturbed mechanics of the knee, which are present both after nonoperative treatment of the ACL and after a reconstruction of the ACL. ) Orthop Sports Phys Ther 2001;3 1:567-576.

Proprioception of the knee was measured in 20 patients with reconstructed anterior cruciate ligaments and in 19 age-matched controls. The mean time from surgery was 2 years. Three tests of proprioception were used: (a) threshold to detection of passive motion from 20 and 40 degrees toward flexion and extension, (b) active reproduction of a 30 degrees passive angle change, and (c) visual reproduction of a 30 degrees passive angle change. The aim was a complete, bilateral, proprioceptive evaluation of patients who had undergone reconstruction of the anterior cruciate ligament. As compared with those in the control group, the knees with reconstructed anterior cruciate ligaments had a higher threshold to detection of passive motion in the extension trials from 20 and 40 degrees (p = 0.0003 and 0.04, respectively) and in the flexion trials from 20 and 40 degrees (p = 0.004 and 0.0008, respectively). When the uninjured knees of the patients were compared with those in the control group, higher values for threshold to detection of passive motion were found in the flexion trials from 20 degrees (p = 0.002) and 40 degrees (p = 0.02). Thus, decreased proprioceptive ability was present in some measurements of these patients after reconstructive surgery, not only in injured knees but also in uninjured knees, as compared with the reference group. The functional relevance of these findings was not investigated in this study, but the results suggest that bilateral proprioceptive considerations should be made when evaluating prognostic factors, treatment, and risk of contralateral knee injury in patients with reconstructed anterior cruciate ligaments.

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Study Design: Nonrandomized prospective study.Objective: To evaluate proprioception in 2 groups of patients with anterior cruciate ligament (ACL) deficiency who had different severity of symptoms. Background: Defective proprioception has previously been found in patients with ACL-deficient knees. It has been suggested that sensory receptors of the ACL and other knee joint ligaments contribute to proprioception and knee joint function and stability. Methods and Measures: A total of 17 patients with ACL deficiency (mean [SDl age, 28.8 t 5.6 years; range, 22-39 years) with few, if any, symptoms were compared with 20 patients with ACL deficiency (mean [SD] age, 26.6 ? 6.1 years; range, 18-39 years) having instability and episodes of giving way. The groups were compared with each other and with an age-matched reference group of 19 nonimpaired subjects. Their mean (SD) age was 25.6 t 3.7 years (range, 20-37 years). Three tests of proprioception were used: threshold to detection of passive motion from 2 starting positions (20" and 40"of knee flexion) toward flexion and extension, active reproduction of a 30" passive angle change, and visual reproduction of a 30" passive angle change. The Wilcoxon rank sum test was used for between-group comparisons. Results: Symptomatic patients had higher threshold to detection of passive motion in their injured side in the flexion trial from 20" (median of 1.5" vs median of 0.57 and in the extension trial from 40' (median of 1 .OO vs median of 0.5" than the asymptomatic patients. No differences were found in the other threshold tests, active or visual reproduction tests. Conclusiw: Patients with severe symptoms related to ACL deficiency were found to have inferior proprioceptive ability in some measurements compared with patients with a good knee function. The findings indicate that proprioceptive deficits might influence the outcome of an ACL injury treated nonoperatively. j Orthop Sports Phys Ther 1999;29:587-594. Key Words: anterior cmciate ligament, proprioception, threshold

A defect in proprioception has been found in selected patient groups that have an anterior cruciate ligament deficient knee at different times after the original injury. The time of development and the extent of such defects were studied longitudinally on 16 consecutive patients. During the first year after a primary knee injury, which included a complete rupture of the anterior cruciate ligament, we repeatedly performed three tests of proprioception: (a) one to determine the threshold for detecting a passive motion from starting positions of 20 and 40 degrees, (b) an active reproduction of a passive angular change, and (c) a visual estimation of a passive angular change. The injured limb was compared with the uninjured limb and with the limbs of an age-matched reference group of healthy subjects. The population did not have a normal distribution, and some patients had consistently extreme recordings in the threshold tests at the various times of testing. Significant differences were found between the groups at the starting position of 20 degrees, when the injured knee was compared with the uninjured knee, after 1 month (p = 0.05), and after 2 months (p = 0.03). There was a trend toward a higher threshold for detecting a passive motion when the injured side was compared with the knees of the reference group at 1 month (p = 0.06) but not later on. A similar pattern was found for the injured knee at the starting position of 40 degrees, but it was not significant. An impaired ability to detect a passive motion was registered for the nearly extended knee 1 and 2 months after a primary injury. In the active reproduction and visual estimation tests, no significant defects were found at any time during the first year in these consecutively studied patients.