LEG PRESS EXERCISE IN PATELLOFEMORAL PAIN- A ONE-YEAR FOLLOW-UP STUDY

Transcription

1 LEG PRESS EXERCISE IN PATELLOFEMORAL PAIN- A ONE-YEAR FOLLOW-UP STUDY Chen-Yi Song 1 and Mei-Hwa Jan 1,2 1 School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan 2 Physical Therapy Center, National Taiwan University Hospital, Taipei, Taiwan Abstract The purpose of this study was to investigate the short- and long-term effect of leg-press exercises in dealing with patellofemoral pain. Sixty subjects with patellofemoral pain participated. They were randomly assigned into leg-press exercise or control (no exercise) group. Training consisted of three weekly sessions for eight weeks. Measurements of pain (VAS), Lysholm scale score, morphology of vastus medialis obliquus (including crosssectional area and volume by ultrasonography) were obtained before and after 8-wk treatment. Long-term follow-ups were carried out (on leg-press group only) at 6-month and 12-month later. Significant improvements in pain, functional score, and muscle hypertrophy were observed after leg-press intervention, but not in the control group. The good subjective and functional outcomes achieved immediately after exercise intervention were maintained at long-term follow-up. Since the short- and long-term prognoses of subjects who underwent leg-press exercise were relatively good, the simple and convenient leg-press exercise was recommended in rehabilitation of patellofemoral pain. KEY WORDS: knee, leg press, morphology. 1

2 INTRODUCTION Patellofemoral pain is a common musculoskeletal problem of the knee that frequently affects both young and sporty populations. It accounts for 25% of all sports-related knee injuries. 1 Patellofemoral pain was thought to occur with lateral malalignment of the patella where hypotrophy or atrophy of vastus medialis obliquus (VMO) muscle was one of possible cause that commonly seen in patients with patellofemoral pain. 2 Since the VMO plays an important role in medial stabilization of patella, 3,4 numerous rehabilitation protocols regarding quadriceps strengthening were described for dealing with this problem. Among them, the legpress exercise was a common approach. 5-7 Despite the large amount of existing literature concerning the conservative management of patellofemoral pain, most of them were not longterm investigation. The clinical evidence regarding the efficacy of simple leg press exercise approach, especially on VMO morphology, was lacking. It is unclear if the improvement of subjective outcome, i.e. decrease of pain and increase of functional ability, is interrelated with the VMO hypertrophy. The purpose of this study was to investigate the short-term (2-month) and long-term (6- and 12-month) effects of leg-press exercise. The morphology of VMO along with the pain and functional ability were measured. 2

3 METHOD Subjects A total of 60 participants diagnosed with unilateral or bilateral patellofremoral pain were enrolled in this study. The inclusion criteria were: (1) experience of anterior or retropatellar knee pain after performing at least two of the following activities: prolonged sitting, stairclimbing, squatting, running, kneeling, hopping/jumping and deep knee flexing; (2) insidious onset of symptoms unrelated to traumatic accident; (3) presence of pain for more than one month; and (4) age of 45 years and under (to eliminate the possibility of osteoarthritis). In addition, participants had to exhibit at least two of the following positive signs of anterior knee pain during the initial physical examination: (1) patellar crepitus; (2) pain following isometric quadriceps contraction against suprapatellar resistance with the knee in slight flexion (Clarke s sign); (3) pain folowing compresion of the patela against the femoral condyles with the knee in full extension (patellar grind test); (4) tenderness upon palpation of the posterior surface of the patella or surrounding structures; (5) pain following resisted knee extension. Participants were excluded if they had: (1) self-reported clinical evidence of other knee pathology; (2) patellar tendonitis or knee plica; (3) a history of knee surgery; (4) central or peripheral neurological pathology; (5) knee radiographic abnormalities (such as knee osteoarthritis) or lower extremity malalignment (such as foot pronation); (6) severe knee pain (VAS>8); (7) received non-steroidal anti-inflammatory drugs, injections or physical therapy in preceding 3 months. All subjects participated in the study after written informed consent provided. This study was proved by the Research Ethics Committee of the National Taiwan University Hospital. Treatment program 3

4 Participants were randomly allocated into leg-press exercise (LP) or control (no exercise) group. Three-weekly exercise interventions were carried out by one physical therapist. Legpress exercises training was performed unilaterally starting from 45 of knee flexion to full extension using leg-press machine (Enraf-Nonius B.V., Rotterdam, The Netherlands) since the patellofemoral joint stress was less in the functional range of knee motion. 8 Prior to the beginning of exercise training, unilateral one-repetition-maximum (1RM) strength of the lower extremity was determined with repetition-to-fatigue testing. Patients were unilaterally trained at 60% of 1 RM for 5 sets of 10 repetitions. For the advancement of training resistance, the 1RM was re-measured every 2 weeks and the exercise intensity adjusted accordingly. A metronome (60 b*min -1 ) was used to control the exercise pace at 2 second concentric and eccentric contractions from 45 of knee flexion to full extension. There was a 2 second break between each repetition and a 2 minute break between each set. Left and right limbs were alternatively trained between each exercise set. A hot pack was applied to quadriceps for 15 minutes before exercise. After exercise, participants were taught to stretch their quadriceps, hamstrings, iliotibial bands and calf muscle groups, and had a cold pack applied to their knee joints for 10 minutes. Self-stretches were maintained for 30 seconds and were repeated 3 times for each muscle group. Control group participants did not receive any exercise intervention, but were provided with health educational material regarding patellofemoral pain. During the intervention period, all participants were advised not to perform or receive any other exercise program or intervention. Neither tape nor brace was used. After that, 8-wk exercise program (the same with that of leg-press group) was then given to control group. The exercise intervention participants then received health education. In addition, simple home exercise programs (including general quadriceps strengthening exercise, i.e. straight leg raise 4

5 and single leg mini-squat, and lower-extremity stretching exercise) were taught, but they were not requested to keep up the program during follow-up period. Outcome measurement Four assessment sessions, at time of initial evaluation (pre-training), 2-month post-training, and 6-month, 12-month later, were performed by another physical therapist who was blinded to each patient s grouping. At long-term follow-up (6- and 12-month), only leg-press exercise group was evaluated. The outcome measures in this study included VAS pain assessment, and the worst pain experienced in the previous week was measured using the 100-mm VAS line. The functional ability was measured by Lysholm scale (0-100 point scale) where 100 point indicating maximal functions. Additionally, VMO morphology, including VMO cross-sectional area (CSA) on the patella-base level and VMO volume under the patella-base level, were assessed by ultrasonography (HDI 5000, Advanced Technology Laboratories, Bothell, WA) with a 5 to 12 MHz broadband linear-array transducer (38 mm). All ultrasonographic measurements were obtained while participants were lying on a bed, with both legs relaxed (feet were positioned in a frame to prevent leg rotation) and a thick padded towel placed underneath the knee to maintain resting position. The longitudinal length of the patella in mm was determined from the upper to the lower border with calipers. The VMO volume under the patella-base was approximated from a series of VMO CSAs using the trapezoidal rule. 9 To obtain a valid calculation of VMO volume from the sonographic image, a custom-made holder was used to fix the probe. 9 The holder was calibrated to quantify movement of the transducer by synchronizing with a scaled hub, which was turned in a full circle to mobilize the transducer by 1 mm from the proximal patellar-base toward the distal patellar-apex along a line perpendicular to the horizontal representing the upper border of the patella. The first VMO 5

6 CSA was taken from the line passing through the patella-base level. Serial VMO CSAs were obtained every 2 mm, until the VMO image on the visual display faded. 5,9 Data Analysis Data obtained from the most symptomatic knee were analyzed using SPSS 11.0 (SPSS, Inc., Chicago, IL). Data were subjected to an intention-to-treat analysis and included all drop-outs. The data of control group gathered at post-training evaluation was then used in long-term follow-ups for comparison with exercise group. Descriptive statistics (mean standard deviation, SD) were used to determine participant characteristics. Prior to statistical analysis, the Kolmogorov-Smirnov test was performed to assess the normality of continuous data. Normally distributed baseline demographic variables were compared independent t-test. Nonnormally distributed variables were compared by Mann-Whitney test with an alpha Gender and numbers of afflicted sides (bilateral vs. unilateral) were compared by Chi-square test with an alpha For each outcome variable measured, a 4 (assessment time) 2 (treatment groups) two-way mixed ANOVA was performed. When a significant two-way interaction was detected, post-hoc analysis was performed using Bonferroni adjustment. 6

7 RESULTS The demographic data for both LP and control group participants was presented in Table 1. There were no significant between group differences, except symptom duration (P= 0.025), for the demographic variables. During 8-wk intervention period, 8 participants dropped out of the study due to personal factors (not knee pain) or work commitment. Fifty-two participants completed the trial (27 in the LP exercise group and 25 in the control group). The follow-up rate was 0.90 in LP and 0.83 in control group at post-intervention evaluation. At 6- and 12-month, the follow-up rate was 0.83 for LP exercise group. The main results of this study were summarized in Figure 1-4, with 4 assessment time in horizontal axis, where 0-month denoted pre-intervention, 2-month denoted post-intervention, and 6-month and 12-month represented the follow-ups. There were no significant betweengroup differences in all outcome measures at baseline (pre-intervention). Significant decreases in pain, increases in functional score and VMO muscle hypertrophy were observed after LP intervention (all P< 0.005), but not in the control group. Only the good subjective and functional outcomes (VAS and Lysholm scale score) achieved immediately after exercise intervention were maintained at long-term follow-up (all P< as compared to preintervention). 7

8 DISCUSSION The use of closed kinetic chain (CKC) exercise for knee rehabilitation has been popular in past several years because it has been thought to be more functional 10 and more effective than open kinetic chain exercise in reducing pain and increasing functionality. 7,11 Furthermore it could induce greater VMO activity 11 and reduce lateral displacement of patella. 10 Therefore, strengthening of the knee extensor (quadriceps), especially the VMO muscle by means of leg press is a very common therapeutic exercise for treating patellofemoral pain. We tended to investigate the effects of LP exercise combined stretching not only on pain and function, but also on the VMO muscle morphology, and to determine if the short-and long-term outcomes were comparable. Present study showed 8-wk LP with stretching exercises significantly decreased pain and increased function at both short-and long-term (1-yr, at least) follow-up. The results were consistent with previous studies where Herrington and colleagues explored the effect of 6-wk progressive LP exercise, 6 and Witvrouw and colleagues examined both the effects at shortterm (5-wk) and long-term follow-up (5-yrs) of a series of CKC exercise program (including LP, double or single one-third knee bend, stationary biking, rowing machine exercise, step up and down exercise, and progressive jumping exercises on mini trampoline) combined with the conventional stretching of quadriceps, hamstrings, and gastrocnemius. 7,13 Based on these results, the short-term clinical effects on pain and function of 5 to 8-wk of CKC exercise or simple leg-press exercise training with or without stretching of lower extremity muscles were determined to be similar. The long-term effect of multiple CKC exercise program was also documented by Witvrouw et al., 13 however, regarding simple LP exercise, especially in safe and functional range, the only data was from the current study. 8

9 In addition, to our knowledge, we were the first to use ultrasonography to examine the therapeutic effect on VMO muscle morphology. This noninvasive and low cost technique is now extensively used for morphological investigations in the field of rehabilitation. 14 Folland and colleagues concluded that the primary morphological adaptation after resistance exercise is related to an increase in the CSA of the whole muscle and individual muscle fibers (caused by an increase in myofibril size and number). 15 The better results of VMO hypertrophy (both CSA on the patella-base level and volume under the patella-base level) were found after 8-wk leg-press training, however, it was lost after 6 to 12-month follow-up time while patients remained less pain and better function compared to pre-training status. It was not surprising that muscle became hypertrophy as a result of LP strengthening. Our LP-group patients demonstrated significant gains in muscle strength, from to kg, as determined by assessing the 1RM during the intervention period. In the uncontrolled followup period, simple home exercise programs and healthy education were given, however, we did not monitor if patients continued exercise or not. It could explain, probably, why the VMO became less hypertrophy during the 6- and 12-month follow-up as compared to that achieved after 2-month conservative treatment. Despite the VMO muscle size was less well during both short- and long-term follow-up than before, the pain and functional status were reported to the same as that after the training. According to previous studies, quadriceps function was a premise for a good functional result in patients with patellofemoral pain. 16,17 Natri and colleagues identified a strong correlation between the restoration of the quadriceps strength and the long-term final outcome. 17 The relationship between quadriceps strength and locomotor, or stair-climbing and squatting function in patients with patellofemoral pain has been previously documented. 5,18 Indeed, the 9

10 functional improvements were supported to significantly correlate with the pain reductions. 5,19,20 We speculated that restoration of quadriceps strength, flexibility and adjusted physical activity (life style) taught by health education may contribute to improvement in symptom and function. The possible mechanisms included quadriceps strengthening may help repair abnormalities of patellar tracking or the contact location and pressure distribution, 18 and increase nutritional blood flow. 21 Additionally, stretching exercises may alter patellofemoral joint biomechanics influenced by tightness of quadriceps, hamstrings, calf muscles and the iliotibial band. 22 According to homeostasis theory proposed by Dye, 23 patients could become pain-free once they function within the envelope of function, in other words, the load acceptance of the patellofemoral joint. Therefore, adjusted physical activity or life style was also helpful. Since the decrease of pain and increase of functional ability was not interrelated with VMO hypertrophy, this result, on the other hand, pointed out an issue that further research could address on to what extent the VMO hypotrophy or atrophy may response for symptomatic patellofemoral pain with the activity level controlled. That will be of great interest for dealing with patellofemoral pain. Recently, the patient values were emphasized in clinical decision making. Since the pain was the main symptom of patellofemoral pain, the primary goal was to relief the pain of patients. The VAS change of 1.5 over 10-point in patients with patellofemoral pain was the minimal difference to be considered clinically important. 24 While LP and stretching exercise could clinically and significantly decrease the pain, only 11 (37%) of patients in our study got completely pain-free at the 1-yr follow-up. Among them, delayed treatment effect was shown on 4 patients. That is, patients felt better after 2-month training, but were pain-free later. In 10

11 another 5-yr follow-up study by Witvrouw et al., 13 fewer amounts of patients (20%) were cured. The data regarding the chance of benefit from treatment may provide some insight to patients for judge of the treatment alternatives. More researches focused on different physiotherapy approaches, such as taping, bracing were warranted. The study had several limitations. There was no control group during long-term follow-up periods. Only the VMO was examined by ultrasonography after exercise intervention, while the remainder of quadriceps muscle were not. CONCLUSION Te short- and long-term prognoses of subjects who underwent leg-press exercise were relatively good. Therefore, the simple leg-press within 45 degrees of knee flexion, and general lower-extremity stretching exercise were recommended in clinical practice for dealing with patellofemoral pain. The role of VMO as individual muscle or with quadriceps muscle as a whole in mediating patellofemoral pain needed to be clarified by more evidence. 11

12 REFERENCES: 1. Fredericson M, Yoon K. Physical examination and patellofemoral pain syndrome. Am J Phys Med Rehabil. 2006;85: Witvrouw E, Werner S, Mikkelsen C, et al. Clinical classification of patellofemoral pain syndrome: guidelines for non-operative treatment. Knee Surg Sports Traumatol Arthrosc. 2005;13: Lieb FJ, Perry J. Quadriceps function. An anatomical and mechanical study using amputated limbs. J Bone Joint Surg Am. 1968;50: Toumi H, Poumarat G, Benjamin M, et al. New insights into the function of the vastus medialis with clinical implications. Med Sci Sports Exerc. 2007;39(7): Song CY, Lin YF, Wei TC, et al. Surplus value of hip adduction in leg-press exercise in patients with patellofemoral pain syndrome: A randomized controlled trial. Phys Ther. 2009;89(5): Herrington L, Al-Sherhi A. A controlled trial of weight-bearing versus non-weightbearing exercises for patellofemoral pain. J Orthop Sports Phys Ther. 2007;37(4): Witvrouw E, Lysens R, Bellemans J, Peers K, Vanderstraeten G. Open versus closed kinetic chain exercises for patellofemoral pain. Am J Sports Med. 2000;28(5): Grelsamer R, Klein J. The biomechanics of the patellofemoral joint. J Orthop Sports Phys Ther. 1998;28: Lin YF, Lin JJ, Cheng CK, Lin DH, Jan MH. Association between sonographic morphology of vastus medialis obliquus and patellar alignment in patients with patellofemoral pain syndrome. J Orthop Sports Phys Ther. 2008;38: Doucette SA, Child DD. The effect of open and closed chain exercise and knee joint position on patellar tracking in lateral patellar compression syndrome. J Orthop Sports 12

13 Phys Ther. 1996; 23: Stiene HA, Brosky T, Reinking MF, et al. A comparison of closed kinetic chain and isokinetic joint isolation exercise in patients with patellofemoral dysfunction. J Orthop Sports Phys Ther. 1996;24(3): Hodges PW, Richardson CA. The influence of isomeric hip adduction on quadriceps femoris activity. Scand J Rehab Med. 1993; 25: Witvrouw E, Danneels L, Tiggelen DV, Willems TM, Cambier D. Open versus closed kinetic chain exercises in patellofemoral pain. A 5-year prospective randomized study. Am J Sports Med. 2004;32(5): Whittaker JL, Teyhen DS, Elliott JM, et al. Rehabilitative ultrasound imaging: understanding the technology and its applications. J Orthop Sports Phys Ther. 2007;37(8): Folland JP, Williams AG. The adaptations to strength training. Morphological and neurological contributions to increased strength. Sports Med. 2007;37(2): Witvrouw E, Lysens R, Bellemans J, et al. Which factors predict outcome in the treatment program of anterior knee pain? Scand J Med Sci Sports. 2002;12: Natri A, Kannus P, Järvinen M. Which factors predict the long-term outcome in chronic patellofemoral pain syndrome? A 7-yr prospective follow-up study. Med Sci Sports Exerc. 1998;30(11): Powers CM. Rehabilitation of patellofemoral joint disorders. J Orthop Sports Phys Ther. 1998;28(5): Alaca R, Yilmaz B, Goktepe AS, Mohur H, Kalyon TA. Efficacy of isokinetic exercise on functional capacity and pain in patellofemoral pain syndrome. Am J Phys Med Rehabil. 2002;81(11): Crossley K, Bennell K, Green S, Cowan S, McConnell J. Physical therapy for 13

14 patellofemoral pain: a randomized, double-blinded, placebo-controlled trial. Am J Sports Med. 2002;30(6): Cutbill JW, Ladly KO, Bray RC, Thorne P, Verhoef M. Anterior knee pain: a review. Clin J Sports Med. 1997;7: Escamilla RF, Fleisig GS, Zheng N, et al. Biomechanics of the knee during closed kinetic chain and open kinetic chain exercises. Med Sci Sports Exerc. 1998;30(4): Dye SF. The pathophysiology of patellofemoral pain. Clin Orthop. 2005;436, Crossley KM, Bennell KL, Cowan SM, Green S. Analysis of outcome measures for persons with patellofemoral pain: which are reliable and valid? Arch Phys Med Rehabil. 2004;85: Acknowledgement We would like thank the support from Nation Science Council in Taiwan for this study. 14

15 Table 1. Demographic Data for Study Participants a LP Control (n= 30) (n= 30) P value Sex (Male:Female) 8:22 4: Age (y/o) 40.2± ± Height (cm) 161.3± ± Weight (kg) 60.1± ± BMI (kg/m 2 ) 23.0± ± Involved side 18:12 18:12 - (Bilateral:Unilateral) Duration of symptoms 38.3± ± * (month) a Data are presented as mean±sd. LP denotes leg press exercise group. 15

16 Figure Legends Figure 1. Comparison between Assessment Time Changes of VAS between Leg Press and Control Groups. Figure 2. Comparison between Assessment Time Changes of Lysholm score between Leg Press and Control Groups. Figure 3. Comparison between Assessment Time Changes of VMO CSA between Leg Press and Control Groups. Figure 4. Comparison between Assessment Time Changes of VMO Volume between Leg Press and Control Groups. 16

17 VAS month 2 month Figure 1. 6 month LP Control 12 month * denotes significant difference compared to 0-month in LP group (P< 0.005). denotes significant difference between LP and control group (P< 0.005). Lysholm scale month 2 month Figure 2. 6 month LP Control 12 month * denotes significant difference compared to 0-month in LP group (P< 0.005). denotes significant difference between LP and control group (P< 0.005). CSA (cm 2 ) LP Control Volume (cm 3 ) LP Control month 2 month 6 month 12 month 0 0 month 2 month 6 month 12 month Figure 3. Figure 4. * denotes significant difference compared to 0-month in LP group (P< 0.005). denotes significant difference between LP and control group (P= 0.018). denotes significant difference compared to 2-month (P= 0.012) and 6-month (P= 0.009) in LP group. * denotes significant difference compared to 0-month in LP group (P< 0.005). denotes significant difference between LP and control group (P= 0.006). denotes significant difference compared to 6-month (P= 0.002) and 12-month (P= 0.001) in LP group. 17