Effects of Recurrent Lateral Ankle Sprains on Active and Passive Judgments of Joint Position

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1 Effects of Recurrent Lateral Ankle Sprains on Active and Passive Judgments of Joint Position MICHAEL T. GROSS The purpose of this study was to examine the effects of recurrent lateral ankle sprains on subjects' active and passive judgments of joint position. Fourteen subjects with recurrent unilateral ankle sprains contributed data to two groups: 1) In Group 1, the subjects' 14 sprained ankles were tested and 2) in Group 2, the same 14 subjects' contralateral nonsprained ankles were tested. An additional seven subjects with no history of injury to either ankle comprised Group 3 with 14 nonsprained control ankles. The experimenter tested all blindfolded subjects with active and passive attempts at replicating predetermined ankle joint positions in the inversion-eversion range of motion. An isokinetic dynamometer measured joint position. A two-way analysis of variance indicated no significant effect caused by ankle injury or noninjury. Passive judgments were significantly better than active judgments of joint position (p <.01) in the nonsprained control group. The results suggest that joint receptors play a dominant role in joint angle detection and that muscle receptors are more valuable in the perception of joint movement. Key Words: Ankle joint, Physical therapy, Sports medicine, Sprains and strains. Dr. Gross is Instructor, Division of Physical Therapy, The University of North Carolina at Chapel Hill, Medical School Wing E 222 H, Chapel Hill, NC (USA). He was a graduate student, Division of Physical Therapy, Department of Medical Allied Health Professions, School of Medicine, The University of North Carolina at Chapel Hill, when this study was conducted. This study was completed in partial fulfillment of Dr. Gross' master's degree, Department of Medical Allied Health Professions, School of Medicine, The University of North Carolina at Chapel Hill. This article was submitted May 29, 1986; was with the author for revision 11 weeks; and was accepted December 16, Potential Conflict Of Interest: 4. With increasing amounts of leisure time and the current emphasis on physical fitness, the incidence of sports injuries has increased dramatically. 1 One of the body parts injured most frequently has been the ankle joint, with the most common injury occurring at this joint being the lateral ankle sprain. Two studies examining injuries among high school athletes reported that 14% of all injuries involved the ankle joint. 2,3 Eighty-five percent of these injuries were sprains, and 85% of the sprains involved the lateral ligaments. One proposed theory suggests that recurrent sprains of the same ankle may be the result of altered position sense and postural reflexes secondary to the initial injury. 4 These researchers have identified joint receptors in the ligaments and joint capsules of the ankle and knee joints of the cat, which vary their rates of electrical discharge according to joint position. The same receptors have been linked to the postural reflexes of muscles acting on these joints. Freeman and associates have suggested that because the tensile strength of these joint receptors is less than the connective tissue in which they are imbedded, the joint receptor organs also must be disrupted when ankle ligaments and capsule are stretched or torn. 4 The resulting decrease in sensory input from these receptors then may lead to faulty positioning and diminished postural reflex responses, thereby increasing the probability of injury recurrence. A "sensory retraining" rehabilitation program for ankle sprains based on this theory of injury recurrence has been advocated in the literature. 4,5 Researchers have reported that several types of receptors play a dominant role in signaling joint position. 6 " 23 The two general classes of receptors that have been implicated in contributing to joint position sense are joint receptors and muscle receptors. Freeman and Wyke developed a classification scheme of four types of articular end organs. 6 Their Type 1 slow-adapting receptors provided a simple model for joint position sense. This receptor displayed a characteristic rate of discharge dependent on joint angle. Several other researchers have replicated these results, 7 " 9 and additional studies with animals have indicated that sensory input from articular receptors is projected to the primary sensory areas of the cerebral cortex and to the cerebellar cortex Additional support for the dominant role of joint receptors in signaling joint position has come from human studies involving the introduction of anesthesia into the joint capsule 14 " 17 and the transection of articular nerves in animals. 18 Under both conditions, serious defects in joint position sense and in postural reactions were observed. Another body of literature has stressed the importance of muscle receptors in signaling joint position. Similar to the studies of the joint receptors, some studies have demonstrated reliably that muscle afferents do project their input to the central nervous system. 19,20 Several studies have reported the effects of joint capsule anesthesia on position sense as a way of eliminating the contribution of joint receptors, thereby assessing muscle afferent input. 14,15,17,21 These studies have demonstrated that the perception of movement is retained, although the ability to identify joint position in space is impaired. The application of a vibratory stimulus to muscle has produced the perception of illusory movement, 21 as has the application of tension to long finger flexor muscles during carpal tunnel surgery under local anesthesia. 22 Several studies have reported an agerelated decline in position sense as meas- Volume 67 / Number 10, October

2 ured by threshold of passive knee-joint movement and by the ability of subjects to reproduce passive knee-joint positioning Some of these same studies have reported that patients with degenerative changes in the knee joint demonstrated diminished position sense when compared with age-matched controls. 24,25 Only one study in the literature has attempted to examine the effects of traumatic joint injury on position sense. Glencross and Thornton reported losses in position sense in the sprained ankles of subjects with unilateral injuries. 26 Position sense was measured as the ability of the subject to replicate actively the passive positioning of the ankle in the dorsiflexion-plantar flexion range of motion. The instrument used for the measurement of angular displacement was a standard goniometer, and no measure of instrument or experimenter reliability was reported. Both active and passive positioning always were initiated from the same point in the ROM, possibly providing subjects with temporal cues. Finally, no attempt was made to investigate or to control for active versus passive judgments of joint position. The purpose of this study was to examine the effects of recurrent lateral ankle sprains on subjects' active and passive judgments of joint position. The study was undertaken to investigate the validity of the theory proposed by Freeman and associates 4 and to investigate the possible role of muscle and joint afferents in active and passive judgments of joint position. The following three null hypotheses were posed: 1. Recurrent lateral ankle sprain injuries have no significant effect on judgments of joint position. 2. Active judgments of joint position do not differ significantly from passive judgments of joint position. 3. No significant interaction between recurrent lateral ankle sprain injury and active-passive testing condition exists that affects judgments of ankle joint position. METHOD Subjects Subjects for this study were volunteer students and employees of The University of North Carolina at Chapel Hill. The subjects were between the ages of 18 and 35 years (X = 20.8 years). Individuals who had sustained a recurrent lateral ankle sprain and who had no history of injury to the contralateral ankle were identified as potential subjects by the sports medicine athletic training staff, which serves the general student population at the university. A recurrent lateral ankle sprain was defined operationally as two or more sprains involving the lateral ligament complex and, according to the criteria of Garrick, 27 included: 1) swelling over the lateral aspects of the ankle, 2) pain with active ankle movements, 3) inability to toeraise unilaterally with symmetry, and 4) a limping gait. Persons with any history of a peripheral neuropathy were excluded from participation in the study. The Committee for the Protection of the Rights of Human Subjects at The University of North Carolina at Chapel Hill approved this study, and all subjects signed statements of informed consent before participation. Group 1 consisted of the sprained ankles of 14 subjects (11 men, 3 women) who had sustained a recurrent unilateral ankle sprain involving the lateral ligaments. Group 2 consisted of the contralateral nonsprained ankles of the Group 1 subjects. Group 3 consisted of both ankles of another 7 subjects (2 men, 5 women) who had never sustained any injury to either ankle. Subjects with ankle sprains were not tested until the affected ankle exhibited an absence of swelling and they experienced no pain in the ROM being tested. An absence of swelling was defined operationally as a circumferential figureeight measure of the sprained ankle being no more than 103% of the nonsprained ankle. 24 A 3% differential was used to allow for variation in circumferences not attributable to swelling (ie, joint-capsule thickening, reactive bone formation). Materials and Procedure Subjects were tested with six active and six passive trials for each ankle. The order of ankles being tested and the sequencing of active and passive trials were determined randomly. Two electromyographic biofeedback units* with surface electrodes were used during the passive trials to assist the subjects in maintaining a relaxed state in the muscles that control ankle movements. One set of electrodes was placed over the lateral compartment at a location that was one third of the distance from the fibular head to the lateral malleolus. 28 A * Cyborg Corp, 342 Western Ave, Boston, MA second set of electrodes was placed over the posterior compartment at a midline location that was one third of the distance from the popliteal crease to the level of the lateral malleolus. The experimenter adjusted the audio signal on the lateral compartment of the biofeedback unit so that the signal was barely audible when the subject produced enough eversion force to resist 0.5 lb of medially directed force applied over the fifth metatarsal head with a Newman myometer. Similarly, the baseline audio recording level for the posterior compartment was determined by applying 0.5 lb of laterally directed force over the first metatarsal head. The biofeedback units were turned off for each active trial. The apparatus used for testing was the Cybex II isokinetic dynamometer. The subject was blindfolded and positioned supine, with the calf of the leg to be tested resting on a 12-in high rectangular platform (platform top 7 in wide and 9 in long) (Fig. 1). The bare foot of the subject was strapped to the footrest of the inversion-eversion exercise unit. A 1.5-in diameter piece of orthopedic felt was placed between the retaining strap and the dorsum of the foot so that only the felt disk made contact with the skin. The Cybex II dynamometer then was raised or lowered to a position such that a carpenter's level resting on the subject's tibial crest indicated that the tibial crest was level. Subsequently, the subject's lower leg was secured to the rectangular platform by two Velcro straps. For the passive trials, the subject was instructed to relax the lower leg muscles while the experimenter moved the ankle joint and to listen to the audio signal of the biofeedback units to assist relaxation. The ankle was moved passively by the experimenter (M.T.G.) by placing the exercise unit into one of three test positions (10 of eversion, 10 of inversion, and 20 of inversion). The test position was maintained by the experimenter for 15 seconds. The experimenter then moved the ankle joint twice, first to one extreme of motion, and then to the opposite extreme. As the experimenter moved the ankle back toward the test position, the subject was instructed to say "stop" when he or she felt that the test position had been du- 1 lb = kg. Zimmer Inc, PO Box 708, Warsaw, IN Cybex, Div of Lumex, Inc, 2100 Smithtown Ave, Ronkonkoma, NY in = 2.54 cm PHYSICAL THERAPY

3 RESEARCH across the three groups are represented graphically in Figure 2. Results of the two-way ANOVA for repeated measures for active and passive testing conditions are given in the Table. The F ratios indicated that ankle joint injury-noninjury and active-passive testing condition did not interact significantly to affect the judgment of ankle joint position. Additionally, no significant main effect was present to indicate differences among the three injury-noninjury groups. A significant effect was present, however, indicating that passive judgments of ankle joint position were significantly better (less TE) than active judgments of joint position. The Scheffe test results indicated that a significant difference between active and passive judgments of joint position existed only for Group 3 (F = 10.52; df = 5,78; p <.01). DISCUSSION Fig. 1. Positioning of subject in Cybex II isokinetic dynamometer. Two biofeedback units were used for passive trials, and the digital voltmeter indicated angular displacement. plicated. The subject was tested twice at each of the three test positions for a total of six passive trials. For one of the two trials at each test position, the ankle was moved first to maximum eversion and then to maximum inversion before returning to the test position. These directions of movement were reversed for the remaining trial at the same test position. The examiner performed all passive movements at the speed of 5 /sec. The procedure for the active trials was the same as that for the passive condition, except that the subject actively assumed the test position under the experimenter's verbal direction. The subject then actively moved (5 /sec) away from the test position in the manner described for the passive condition, followed by an attempt to replicate the test position actively. Voltage output from the Cybex II potentiometer* was used to record inversion-eversion ankle positions. The voltage signal of the potentiometer was monitored by a digital voltmeter,# and was calibrated using the goniometric dial mounted on the potentiometer. Calibration was evaluated before each subject was tested. In a pilot study, we # Model , Radio Shack, Div of Tandy Corp, 1 Tandy Center, Fort Worth, TX Volume 67 / Number 10, October 1987 found the voltage signal of the Cybex II potentiometer to be linear within 1%. Test-retest reliability on 20 repeated measures of maximum inversion and maximum eversion by the method used in this study yielded a Pearson productmoment correlation coefficient of.99. Data Analysis For each trial, the absolute difference in degrees of ROM (to the nearest degree) between the test position and the position chosen by the subject was recorded. The sum of the absolute difference measures for the six passive trials yielded a total error (TE) passive sum. A TE active sum was calculated similarly for the six active trials. The data were examined using a twoway analysis of variance (ANOVA) technique for repeated measures on the active-passive testing factor. The TE served as the dependent variable. Post hoc comparisons of means were accomplished with a Scheffe multiple comparison test.29 RESULTS A TE passive measure and a TE active measure were calculated for each subject as described previously. The mean TEs for active-passive testing conditions The ANOVA results indicated that recurrent lateral ankle sprain injuries have no significant effect on judgments of ankle joint position, disregarding differences caused by the active or passive testing condition. This result suggests that the first null hypothesis should be accepted. The absence of a significant main effect because of ankle joint injury-noninjury does not support the Glencross and Thornton study, which reported decreased joint position sense in sprained ankles.26 The lack of agreement may be the result of the absence of control for differences caused by active-passive judgments in the Glencross and Thornton study. Glencross and Thornton used a method that involved the passive positioning of the subject's ankle by the examiner, followed by an active attempt by the subject to replicate the test position. Additionally, Glencross and Thornton did not report the reliability of the manual goniometric measures used in their study. The results indicated the existence of a significant main effect caused by the active-passive testing condition, suggesting that the second null hypothesis should be rejected. Multiple comparisons between means localized this effect to Group 3 only. Passive judgments of ankle joint position were significantly better than active judgments for this control group. The ANOVA indicated a nonsignificant interaction between the active-passive testing and ankle joint injury-noninjury. The third null hypoth1507

4 Active Testing Condition Passive Testing Condition Fig. 2. Means and standard deviations for total error in degrees of range of motion for groups by active-passive testing conditions. Group 1 = unilateral sprained ankles (n = 14), Group 2 = contralateral nonsprained ankles (n = 14), Group 3 = nonsprained control ankles (n = 14). TABLE Analysis of Variance Summary for Total Error Measures position. Muscle receptors are viewed as mechanoreceptors, with frequencies of discharge that increase in response to stretch. 30 Theoretically, the external stretch of a muscle receptor could be decreased by co-contraction of agonist and antagonist muscles even though no joint movement occurred. For muscle receptor input to assist in the detection of joint angle, some central processing of afferent and of agonist and antagonist alpha and gamma efferent signals would be necessary. The linear responses of joint receptors provide a more simplified model of joint angle detection. Quite possibly, therefore, joint receptors may have the dominant role in signaling joint position. Muscle receptors may be more involved in the perception of joint movement and may be less valuable in fine judgments of joint position, as compared with joint receptors. This model may be used to better understand why the TE for active judgments of joint position was significantly greater than the TE for passive judgments for Group 3. The processing and interpretation of additional input from muscle afferent and efferent (alpha and gamma) signals possibly might have resulted in the increased TE for active judgments of joint position. This result may have been similar to the processing and interpretation errors that resulted in judgments of illusory movements in other studies. Reducing this processing and interpretation error by using passive movements and EMG biofeedback may have produced the more accurate judgments of joint position for the passive trials. This model is not applied as easily in explaining why significant differences between active and passive judgments of ankle joint position were not present for the sprained and nonsprained ankles of subjects with unilateral ankle sprains. Theoretically, the results for the nonsprained ankles in Group 2 should have been similar to those of the nonsprained control ankles in Group 3. No significant difference, however, existed between active and passive judgments of joint position in Group 2. This finding suggests either that the two groups were different before injury or that the two groups of subjects were similar before injury and that the ankle sprain injury somehow changed the processing and interpretation strategy of Group 2 subjects. Interestingly, passive TE increased from Group 3, to Group 2, to Group 1. Perhaps with a greater number of subjects, this occurrence would be a statisa p<.01. Source Between subjects Groups Subjects/groups Within subjects Condition Groups x condition Subjects x condition Groups df esis testing for an interaction effect, therefore, was accepted. To explain these results and to relate the results of this study to previous studies is difficult without attempting to construct a model for joint position sense. The literature strongly suggests that joint receptors act as a major contributor to joint position sense. The slowadapting receptor, whose frequency of discharge varies linearly with joint position, could provide reliable information to the CNS for joint angle detection. 6 Perhaps even better support for a major role for joint receptors in position sense has come from joint anesthesia studies These studies have documented increases in thresholds of perceptible movement or complete abolition of sense of movement after joint receptor input was eliminated effectively by local joint anesthesia. The contribution of muscle receptors to joint position sense is more difficult to determine. Two studies reported that SS MS F a 2.22 after joint receptor anesthesia, thresholds of perceptible movement were normal if subjects were allowed to tense their muscles actively. 14,15 Goodwin et al also reported some preservation of perception of movement after local joint anesthesia. 17 They reported, however, that subjects were unable to distinguish between movements at different joints of the same digit. Adding to the difficulty in assigning a role to muscle receptors are studies demonstrating that the perception of illusory movement can be produced by stimulating muscle receptors. The patients with carpal tunnel syndrome studied by Matthews and Simmonds, however, were unable to report at which joint illusory movement had occurred when fingerflexortendons were pulled distally. 22 After considering these studies, a reasonable hypothesis may be that muscle receptors are involved more significantly in the perception of joint movement than in the perception of joint 1508 PHYSICAL THERAPY

5 tically significant trend, and passive TE for Group 1 would be significantly greater than passive TE for both Groups 1 and 2. This result would lend further support to the joint injury theory proposed by Freeman and associates 4 and to a model that assigns a primary role to joint afferents as providers of sensory input regarding joint position. The effect of joint injury on position sense remains unclear, as does the entire question of which receptors contribute to position sense and the manner in which they do so. This study found that ankle sprain injury had no substantial effect on judgments of joint position. This finding did not support the only other study that has addressed this issue. A problem common to both this study and the Glencross and Thornton study 26 is one of inferring causality. Even if deficits in position sense are identified in sprained ankles, this finding is retrospective. Ankle sprain injuries indeed could have caused the deficit. Just as likely, however, is the supposition that the position sense deficit was present before the ankle injury. The deficit may have predisposed the joint to injury or it may have been totally unrelated to the joint injury. A longitudinal experimental design might answer this question of causality. Researchers could evaluate a physically active noninjured group of subjects on measures of active and passive judgments of ankle joint position. Because of the high incidence of ankle sprain injury, many of these individuals would be available for repeated measurement postinjury. Individuals who remained uninjured throughout the study could serve as controls for the repeated measures design. This method would control for the effects of practice, physical training, and maturation. CONCLUSIONS AND CLINICAL IMPLICATIONS The results of this study indicate that ankle sprain injuries do not significantly affect an individual's ability to judge ankle position. Passive judgments of ankle joint position, however, were significantly better than active judgments of joint position among subjects who never experienced ankle sprain injuries. A model was proposed in which joint receptors play a dominant role in joint angle detection and muscle receptors become more valuable in the perception of joint movement. A longitudinal experimental design was suggested to shed further light on the effects of joint injury on position sense. Clinicians may find greater error by patients during active tests of joint position compared with tests involving passive movements of the patient by an examiner. Acknowledgments. I thank Seletha Mebane and Joyce Lyons for the preparation of the manuscript and Ruth Eden for the preparation of the Figures. REFERENCES 1. Vinger P, Hoerner EF: Sports Injuries: The Unthwarted Epidemic. 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J Physiol (Lond) 260: , 1976 Volume 67 / Number 10, October