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The Effect of a Simulated Knee Joint Effusion on Postural Control in Healthy Subjects Riann M. Palmieri, MS, ATC, Christopher D. Ingersoll, PhD, ATC, Mitchell L. Cordova, PhD, ATC, Stephen J. Kinzey, PhD, Marcus B. Stone, MS, ATC, B. Andrew Krause, PhD, ATC ABSTRACT. Palmieri RM, Ingersoll CD, Cordova ML, Kinzey SJ, Stone MB, Krause BA. The effect of a simulated knee joint effusion on postural control in healthy subjects. Arch Phys Med Rehabil 2003;84:1076-9. Objective: To determine the effects of a simulated knee joint effusion on center of pressure (COP) path and mean power frequency (MPF) during standing. Design: Quasi-experimental design. Setting: Sports injury research laboratory in a university setting. Participants: Twenty healthy volunteers, 10 of whom (age, 20.1⫾2.4y; height, 168.0⫾8.1cm; weight, 70.4⫾13.3kg) were assigned to an effusion group and 10 of whom (age, 25⫾3.8y; height, 169.4⫾8.9cm; weight, 74.7⫾7.7kg) were assigned to a control group. Interventions: COP data were collected before and after a 60-mL injection of sterile saline into the knee joint space. Main Outcome Measures: COP path and mediolateral and anteroposterior MPF. Results: COP path decreased after the effusion (pre-effusion mean, 92.2⫾21.9cm; posteffusion mean, 77.27⫾23.0cm). No change was found within the control group for COP path (P⬎.05). No differences were detected before or after joint effusion when the MPF was examined (P⬎.05). Conclusions: Possible explanations for the improved postural control after the effusion include additional somatosensory feedback, an augmented neural drive to the soleus, and/or increased capsular tension. Key Words: Balance; Muscles; Proprioception; Rehabilitation; Somatosensory disorders. © 2003 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation OSTURAL CONTROL is a complex process that requires central processing of sensory inputs from visual, vestibular, P and somatosensory pathways, as well as a resultant efferent response, which controls the precise recruitment of specific motor units.1-4 Somatosensory input originates from the periphery and involves a multitude of receptors, including tactile sensory organs and mechanoreceptors. Tactile receptors function to detect sensations of touch, pressure, and vibration,
From the Sports Medicine/Athletic Training Research Laboratory, Department of Human Services, University of Virginia, Charlottesville, VA (Palmieri, Ingersoll); Sports Injury Research Laboratory, Department of Athletic Training, Indiana State University, Terre Haute, IN (Cordova, Stone); Department of Kinesiology, California State University, San Bernardino, CA (Kinzey); and Department of Athletic Training, Northeastern University, Boston, MA (Krause). No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated. Reprint requests to Riann Palmieri, MS, ATC, University of Virginia, PO Box 400407, 210 Emmet St S, Charlottesville, VA 22904-4407, e-mail:
[email protected]. 0003-9993/03/8407-7719$30.00/0 doi:10.1016/S0003-9993(03)00129-1
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whereas mechanoreceptors perceive the position and movement rate of the various body segments.5 Somatosensation is key in the maintenance of balance, because the postural control system uses the sensory information related to movement and posture from the peripheral sensory receptors.5 Joint effusion commonly follows acute trauma, chronic degenerative joint disease, and surgical intervention. Reflex inhibition of the quadriceps after an acute knee joint effusion is well documented.6-9 This neuromuscular response, termed arthrogenic muscle inhibition, is accompanied by an increased neuromuscular drive to the soleus.6,10 Because of the importance of the soleus in preserving postural stability, it may be possible that the increased neuromuscular activity found within this muscle after a knee joint effusion may enhance one’s ability to maintain postural control. An alteration in somatosensory feedback is likely after a knee joint effusion. The fluid within the joint may activate capsular receptors, which could modify the afferent feedback from mechanoreceptors situated inside the effused knee joint. If a modification in afferent feedback does occur, the efferent response produced by the central nervous system (CNS) may be altered, resulting in a change in postural stability. Currently, no information is available on how knee joint effusion affects postural control. Therefore, the purpose of this study was to determine how simulated knee joint effusion influences the postural control of subjects performing a singlelegged stance. METHODS Participants Volunteers were 20 healthy, neurologically sound college students, with no history of lower-extremity surgery and no lower-extremity injury 12 months before the study. Subjects were selected from a sample of convenience. When asked to participate in our study, some potential subjects were hesitant to be placed in the effusion group; therefore, we had to select people for the effusion group who were willing to be injected. All subjects were instructed to refrain from ingesting any stimulating or depressing substances 24 hours before data collection. Additionally, participants were asked not to exercise on the day of data collection. Each subject provided informed consent after the purpose of the study was explained. The protocol was approved by the School of Health and Human Performance Human Subjects Review Committee at Indiana State University. Instrumentation A Kistler piezoelectric force platforma was used to gather center of pressure (COP) data. Eight raw-voltage signals were sampled (100Hz), electronically processed, and amplified (gain set at 1000) by the Kistler amplifier. The amplifier was interfaced through an analog-to-digital converter positioned within a microcomputer. The data were electronically processed by the Ariel Performance Analysis Systemb into anteroposterior (AP) and mediolateral (ML) COP values. Additional softwarec
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was used to convert the time-domain data into the equivalent frequency domain by using a fast Fourier transformation. Protocol Before testing, the procedures and risks of the study were explained to all subjects. Subjects were assigned to 1 of 2 groups: the effusion group (6 men, 4 women; age, 20.1⫾2.4y; height, 168.0⫾8.1cm; weight, 70.4⫾13.3kg) or the control group (5 men, 5 women; age, 25⫾3.8y; height, 169.4⫾8.9cm; weight, 74.7⫾7.7kg). Testing for the effusion group took place before testing for the control group. Testing was performed on the subject’s self-reported dominant limb, which, in all cases, was the right leg. Subjects were oriented to the forceplate and its surroundings, to eliminate touchdowns by the nondominant limb. During pilot testing, we discovered that, for subjects to maintain a single-legged stance, it was necessary to install a safety bar. The safety bar appeared to provide a sense of security for the participants. Subjects were able to tap this bar with 1 hand if they began to feel unstable. If more than 1 tap occurred during a trial or if the tap was longer than 1 second, the trial was discarded and repeated. Participants were instructed to touch this bar only if they were going to fall and not to touch down onto the platform with the nondominant limb. If the subject happened to touch down with the nonstance limb, the trial was discarded and repeated. Each subject was required to stand quietly on the forceplate with his/her foot positioned in the center. The participant was instructed to stand on the test leg with hands on hips and eyes closed. All subjects wore opaque goggles during testing to minimize input from the visual system. Each subject performed a 10-second standing trial 5 times, with a 30-second rest between trials. After collecting baseline measurements, subjects in the control group rested for 8 minutes (the approximate length of the injection procedure) while subjects in the effusion group were readied for the injection. An area superolateral to the patella was cleaned with alcohol and povidone-iodine (Betadine). Using a sterile disposable syringe, 3mL of 1% lidocaine was injected subcutaneously for anesthetic purposes. With a second disposable syringe, 60mL of sterile saline was injected through the superolateral knee joint capsule into the joint space. An effusion wave was then performed to ensure that the effusion was within the knee joint.10 After the injection or the period of rest, subjects performed 5 additional 10-second trials by following the same procedures described previously. Data Reduction The data for each testing condition were downloaded onto a desktop computer by using the Microsoft Excel spreadsheet program.d The derived COP parameters used to quantify alterations in postural control were then calculated. Three COP variables were derived from the displacement of the COP. The COP path is the total distance traveled by the COP over the course of the trial. The COP path was calculated by summing the actual distance between successive COP locations. A comprehensive explanation on the calculation of COP path is described by Hufschmidt et al.11 A fast Fourier transformation (Blackman ⫺92dB filter, zeropadded, with linear amplitude and the mean removed) was used to determine the spectral characteristics of postural control. The AP and ML mean power frequency (MPF), which is the weighted average of the power at each of the harmonic com-
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ponents contained within the power spectrum of the signal,12 was then determined by means of the following formula: 共F1 䡠 P1⫹F2 䡠 P2. . .⫹Fn 䡠 Pn兲 共P1⫹P2⫹. . .⫹Pn兲 In this formula, each frequency (F) component (measured in hertz) is weighted by its power (P⫺the amplitude value corresponding to its respective F; measured in centimeters). MPF⫽
Statistical Analysis A 2⫻2 repeated-measures (on time) multivariate analysis of variance was performed to evaluate whether time and group differed on COP path, AP MPF, or ML MPF. Univariate F tests and paired-sample t tests were used post hoc to locate specific group differences. The ␣ level was set a priori at P less than or equal to .05. RESULTS No subject expressed any discomfort during testing. The day after injection, some subjects stated that they were sore at the site of injection but were able to continue normal daily activity. After the injection, subjects described the knee as being “full” or “tight.” It is interesting to note that 9 of the 10 subjects stated that they felt “more stable” after the knee joint effusion when they performed the single-legged stance, which corresponds with the quantitative data. Additionally, no subject touched the safety bar after the joint effusion, and 2 touches were recorded (each by a different subject) before effusion. These “touch” trials were examined, and no differences were noted in the COP derivatives calculated for these trials and the subjects’ other 4 trials. No touches were noted for the control group. Figure 1 depicts the mean COP path for both groups before and after the intervention (effusion or rest). A time by group interaction (F1,18⫽9.88, P⫽.006, 2⫽.354) was detected. A main effect for time was also found with regard to COP path (F1,18⫽7.20, P⫽.015, 2⫽.286). COP path decreased for the effusion group after the injection (t9⫽3.402, P⫽.008). No time difference was noted for the control group (t9⫽⫺.446, P⫽.666). Figures 2 and 3 depict the mean ML and AP MPF for both groups before and after the intervention. Times did not differ for ML (F1,18⫽.163, P⫽.691, 1⫺⫽.067, 2⫽.010) or AP (F1,18⫽.032, P⫽.861, 1⫺⫽.053, 2⫽.006) MPF. No differences were detected between the effusion and control groups for any of the COP derivates before intervention (P⬎.05). DISCUSSION Our study was undertaken to examine how artificial knee joint effusion may affect postural control. After the injection of 60mL of sterile saline into the knee joint capsule, a decrease in COP path was observed. This suggests that, in the presence of an acute, noninflammatory knee joint effusion, the subjects’ ability to maintain a single-legged stance was enhanced. When considering the results of this study, it is important to realize that the same results may not be seen if a knee joint effusion accompanied joint damage. Knee proprioception is compromised after anterior cruciate ligament injury and chronic joint degeneration, presumably because of the disruption of the mechanoreceptors.13 An effusion often accompanies these injuries and may not enhance postural steadiness under these conditions because of the damaged mechanoreceptors and/or the perceived pain. After knee joint effusion, an increase in the soleus H-reflex has been seen, which suggests an increased availability of Arch Phys Med Rehabil Vol 84, July 2003
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Fig 1. Means and standard deviations (SDs) for the COP path length before and after the injection of saline into the knee joint space for the effusion group. The COP path was significantly lower after the injection (P.05).
alpha motoneurons.6,10 The augmented neuromuscular drive to the soleus may have contributed to the increased postural stability found in our study. However, an increase in the H-reflex does not reflect enhanced control. It simply suggests that more motoneurons are available to be recruited. Therefore, although this hypothesis is appealing, further research is needed to determine whether the increased motoneuron pool availability contributes to the improved postural stability detected in our study. Introducing the simulated knee joint effusion resulted in subjects describing the knee feeling full or tight. This suggests that capsular tension was increased at the joint. Increased tension at or within a joint has been suggested to increase proprioceptive control.14,15 Enhancing proprioceptive feedback would likely increase postural steadiness, because this feedback plays a crucial role in the maintenance of postural stability. An additional mechanism contributing to the improved postural control may be an altered response of joint tactile receptors and mechanoreceptors. Several studies16,17 have shown that application of a knee brace or sleeve improves postural control. The mechanism behind the increased postural steadiness has been attributed to the added somatosensory cues provided by the brace or sleeve. The knee joint effusion examined in this investigation may have acted as an “internal knee sleeve.” The receptors stimulated with an intra-articular effusion (primarily pacinian corpuscles and Ruffini’s endings) would differ from those affected by the knee sleeve (cutaneous receptors); however, the afferent responses relayed to the CNS may be processed similarly, thereby executing a similar efferent response. A study by McNair et al18 found that injection of 90mL of saline into the joint space did not alter subjects’ ability of the Arch Phys Med Rehabil Vol 84, July 2003
effused limb to actively track a passively moving noneffused limb. These results suggest that proprioception was unaffected after joint effusion. The most obvious reason for the different results between their study and ours has to do with the variation in testing procedures. McNair chose to measure a component of proprioception often referred to as kinesthesis, which is the perceived sensations of joint movements and angular positions.19 We chose to assess postural control, which is not a direct measure of proprioception. The postural control system relies on somatosensory, visual, and vestibular cues to execute a strategy necessary to maintain postural equilibrium.19,20 Additionally, testing in the McNair study was performed in a non–weight-bearing position, whereas our methods placed the knee joint in a loaded position, which may also account for the different results. The simulated knee joint effusion did not significantly influence the AP or ML MPF. The lack of a significant change in the frequency characteristics of the COP variables suggests that (1) somatosensation was not affected by the knee effusion or (2) MPF is not a sensitive indicator of changes occurring in the somatosensory system. We believe the latter to be true. When examining the shape of the fast Fourier transformation, a notable change is seen around 0.7 to 1.2Hz in the AP direction. This frequency range was described by Nashner21 to be where the somatosensory system functions. Using a different method to examine the spectral characteristics of COP variants may be warranted when attempting to examine the frequency ranges of the working sensory modalities. It should be noted that data for the effusion group were collected before the data for the control group. Although a time effect is unlikely, we felt that it was important to note as a potential weakness of this study.
Fig 2. Means and SDs for ML MPF before and after the intervention. No significant differences were noted for ML MPF for the effusion or control group (P>.05).
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Fig 3. Means and SDs for AP MPF before and after the intervention. No significant differences were noted for AP MPF for the effusion or control group (P>.05).
CONCLUSIONS The results of this investigation suggest that introduction of a simulated knee joint effusion improves postural steadiness. The added somatosensory feedback, augmented neural drive to the soleus, and increased capsular tension created by the effusion are possible explanations for the enhanced postural control. Future research should be conducted to determine the exact mechanism responsible for the improved postural stability. References 1. Horak FB, Nashner LM, Diener HC. Postural strategies associated with somatosensory and vestibular loss. Exp Brain Res 1990;82: 167-77. 2. Winter DA. A.B.C. (anatomy, biomechanics and control) of balance during standing and walking. Waterloo (ON): Waterloo Biomechanics; 1995. 3. Diener HC, Dichgans J, Guschlbauer B, Mau H. The significance of proprioception on postural stabilization as assessed by ischemia. Brain Res 1984;296:103-9. 4. Palmieri RM, Ingersoll CD, Stone MB, Krause BA. Center-ofpressure parameters used in the assessment of postural control. J Sport Rehabil 2002;11:51-66.
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5. Reimann BL, Guskiewicz KM. Contribution of the peripheral somatosensory system to balance and postural equilibrium. In: Lephart SM, Fu FH, editors. Proprioception and neuromuscular control in joint stability. Champaign (IL): Human Kinetics; 2000. p 37-51. 6. Hopkins JT, Ingersoll CD, Krause BA, Edwards JE, Cordova ML. Effect of knee joint effusion on quadriceps and soleus motoneuron pool excitability. Med Sci Sports Exerc 2001;33:123-6. 7. Hopkins JT, Ingersoll CD, Edwards JE, Klootwyk TE. Cryotherapy and transcutaneous electric neuromuscular stimulation decrease arthrogenic muscle inhibition of the vastus medialis after knee joint effusion. J Athl Train 2002;37:25-31. 8. Spencer JD, Hayes KC, Alexander IJ. Knee joint effusion and quadriceps reflex inhibition in man. Arch Phys Med Rehabil 1984;65:171-7. 9. deAndrade JR, Grant C, Dixon AJ. Joint distension and reflex muscle inhibition in the knee. J Bone Joint Surg Am 1965;47: 313-22. 10. Hopkins JT, Ingersoll CD, Edwards JE, Cordova ML. Changes in soleus motoneuron pool excitability after artificial knee joint effusion. Arch Phys Med Rehabil 2000;81:1199-203. 11. Hufschmidt A, Dichgans J, Mauritz KH, Hufschmidt M. Some methods and parameters of body sway quantification and their neurological applications. Arch Psychiatr Nervenkr 1980; 228:135-50. 12. Carpenter MG, Frank JS, Winter DA, Peysar GW. Sampling duration effects on centre of pressure summary measures. Gait Posture 2001;13:35-40. 13. Birmingham TB, Inglis JT, Kramer JF, Vandervoort AA. Effect of a neoprene sleeve on knee joint kinesthesis: influence of different testing procedures. Med Sci Sports Exerc 2000;32:304-8. 14. Ferrell W, Gandevia S, McCloskey D. The role of joint receptors in kinaesthesia when intramuscular receptors cannot contribute. J Physiol 1987;386:63-72. 15. Barret DS, Cobb AG, Bentley G. Joint proprioception in normal, osteoarthritic and replaced knees. J Bone Joint Surg Br 1991;73: 53-6. 16. Birmingham TB, Kramer JF, Kirkley A, Inglis T, Spaulding SJ, Vandervoort AA. Knee bracing after ACL reconstruction effects on postural control and proprioception. Med Sci Sports Exerc 2001;33:1253-8. 17. Kuster MS, Grob K, Kuster M, Wood GA, Gachter A. The benefits of wearing a compression sleeve after ACL reconstruction. Med Sci Sports Exerc 1999;31:368-71. 18. McNair PJ, Marshall RN, Maguire K, Brown C. Knee joint effusion and proprioception. Arch Phys Med Rehabil 1995;76: 566-8. 19. McCloskey DI. Kinesthetic sensibility. Physiol Rev 1978;58:763820. 20. Lephart SM, Pincivero DM, Rozzi SL. Proprioception of the ankle and knee. Sports Med 1998;25:149-55. 21. Nashner LM. Sensory feedback in human posture control. Cambridge: Massachusetts Inst Technol; 1989. Suppliers a. Kistler Instrument Corp, 75 John Glenn Dr, Amherst, NY 14228. b. Ariel Dynamics Inc, 6 Alicante St, Trabuco Canyon, CA 92679. c. AcqKnowledge, version 3.57; Biopac Systems Inc, 42 Aero Camino, Santa Barbara, CA 93117. d. Microsoft Corp, One Microsoft Way, Redmond, WA 98052.
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