Journal of Sport Rehabilitation, 2015, 24, 428 -433 http://dx.doi.org/10.1123/jsr.2014-0184 © 2015 Human Kinetics, Inc.
CRITICALLY APPRAISED TOPIC
Does the Addition of Hip Strengthening to a Knee-Focused Exercise Program Improve Outcomes in Patients With Patellofemoral Pain Syndrome? Ben A. Bloomer and Chris J. Durall Clinical Scenario: Patellofemoral pain syndrome (PFPS) is one of the most common disorders affecting the lower extremities. To improve function and decrease pain, affected individuals often undergo a guided rehabilitation program. Traditional programs have concentrated on quadriceps strengthening and other knee-focused exercises, but recent literature suggests that adding hip-muscle strengthening may improve outcomes. This review was conducted to determine the extent to which current evidence supports the addition of hip-muscle strengthening to a knee-focused strengthening and stretching program in the treatment of PFPS. Focused Clinical Question: Does the addition of hip-muscle strengthening to a knee-focused strengthening and stretching program improve outcomes in patients with PFPS? Keywords: patella, rehabilitation, resistance training
Clinical Scenario Patellofemoral pain syndrome (PFPS) is one of the most common disorders affecting the lower extremities.1–8 To improve function and decrease pain, affected individuals often undergo a guided rehabilitation program. Traditional programs have concentrated on quadriceps strengthening and other knee-focused exercises, but recent literature suggests that adding hip-muscle strengthening may improve outcomes.1–8 This review was conducted to determine the extent to which current evidence supports the addition of hip-muscle strengthening to a knee-focused strengthening and stretching program in the treatment of PFPS.
Focused Clinical Question Does the addition of hip-muscle strengthening to a kneefocused strengthening and stretching program improve outcomes in patients with PFPS?
Summary of Search, “Best Evidence” Appraised, and Key Findings The literature was searched for studies that directly compared knee-focused exercise (strengthening and stretching) combined with hip strengthening with The authors are with the Doctor of Physical Therapy Program, University of Wisconsin–La Crosse, La Crosse, WI. Address author correspondence to Ben Bloomer at benbloomer8@ gmail.com. 428
knee-focused exercise alone in the management of PFPS. The search yielded 4 level 1b randomized controlled trials (RCTs) that directly compared pain and functional outcomes between these 2 exercise interventions. In all 4 of the reviewed studies, the addition of hip-muscle strengthening to a knee-focused exercise program resulted in superior outcomes in pain and function.
Clinical Bottom Line Current high-quality evidence supports the addition of hip-muscle strengthening to knee-focused strengthening and stretching for individuals with PFPS to help reduce pain and improve function. Based on the reviewed literature, clinicians should consider exercises for the hip abductors (eg, side-lying and standing hip abduction with TheraBand or ankle weights), external rotators (eg, seated external rotation with TheraBand), and extensor muscles (eg, hip-extension machines) when treating patients with PFPS.1–4 Clinicians should also use kneefocused strengthening exercises (eg, squats, lunges, quadriceps sets, step-ups, terminal knee extension) and stretching exercises for the hamstrings, iliotibial band, gastrocnemius, and quadriceps.1–4 For the strengthening exercises, 2 to 4 sets of 10 to 15 repetitions should be performed. The stretching exercises should be held for 30 seconds and performed 3 times consecutively a minimum of 3 times per week for 4 weeks.1–4 Strength of Recommendation: Level 1 evidence from 4 RCTs supports the addition of hip-muscle strengthening to a knee-focused strengthening and stretching program to improve pain and function in patients with PFPS. Although the statistical difference between the 5 exercise interventions (knee-focused vs
Hip Strengthening, Knee-Focused Exercise, and PFPS 429
hip plus knee) was significant in all 4 studies, the effect size in 3 of the studies was small, suggesting that the clinical difference between the 2 approaches may be somewhat nominal.
Search Strategy Terms Used to Guide Search Strategy
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• Patient/Client group: subjects and patellofemoral pain syndrome • Intervention/Assessment: hip strengthening and knee-focused strengthening and stretching • Comparison: knee-focused strengthening and stretching alone • Outcome(s): pain and function
Sources of Evidence Searched • PubMed • CINAHL Plus • SPORTDiscus • MEDLINE • Alt HealthWatch • EBSCOhost • Cochrane Database of Systematic Reviews • PsycINFO • Additional resources obtained via manual search of reference lists
Inclusion and Ex9clusion Criteria Inclusion Criteria • At least 2 clinical signs of PFPS (anterior or retropatellar knee pain during ascending/descending stairs, squatting, running, kneeling, hopping/ jumping, and prolonged sitting) • Insidious onset of knee pain unrelated to trauma and persistent for at least 4 weeks • Studies that compared knee-focused exercises with knee-focused exercises plus hip-muscle strengthening • Limited to humans • Limited to English language • Limited to the last 10 years (2005–2014)
Exclusion Criteria • Participants with other concomitant pathological conditions of the knee or hip (eg, meniscus or ligamentous involvement, arthritis) or previous knee or hip surgery. • Studies that only compared knee-focused exercises with hip-muscle strengthening.
Results of Search Many relevant studies were retrieved, but only 4 studies that met eligibility requirements1–4 were selected for review. These are summarized in Table 1. All 4 studies directly compared knee-focused exercises alone with knee-focused exercises combined with hip-muscle strengthening to address PFPS.
Best Evidence The studies in Table 2 were identified as the best evidence for this review. All 4 articles were level 1b evidence RCTs based on Centre for Evidence-Based Medicine 2009 criteria.
Implications for Practice, Education, and Future Research In each of the 4 reviewed studies, patients with PFPS demonstrated statistically significant improvements in pain and function in response to either a knee-focused exercise program or a combined knee- and hip-musclestrengthening program.1–4 However, the improvements were significantly greater in the groups that performed hip-strengthening exercises. The pooled effect sizes of the 4 studies were 0.53 and 0.48 for pain and function, respectively (Figures 1 and 2), suggesting that clinical differences between these exercise approaches may be somewhat modest. It is worth noting, however, that the 1 study (Fukuda et al3) with a large effect size (>0.80 for pain and function) was also the only study with long-term follow-ups. In that study, Fukuda et al3 reported that both groups improved at the 3- and 6-month follow-ups, but only the hip-plus-knee-exercise group demonstrated improvements at the 12-month follow-up. The other 3 studies examined in this review, which had shorter follow-up periods (4 or 6 wk), had smaller betweengroups effect sizes for pain and function. Thus, additional data are needed to ascertain if differences in outcomes between the 2 exercise approaches are more pronounced in the long term. Fukuda et al3 was also the only study in which participants used a hip-extension machine, suggesting that hip-extensor exercise may be particularly beneficial for individuals with PFPS. It is also plausible that larger samples may yield larger between-groups effect sizes in the short term. Table 1 Summary of Study Designs of Retrieved Articles Level of evidence
Study design
Number located
Reference
1b
RCT
4
Nakagawa et al1
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Fukuda et al2 Fukuda et al3 Ismail et al4
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Randomized controlled trial
14 patients (M = 4, F = 10) with a mean age of 24 y (range 17–40) clinically diagnosed with PFPS and randomly assigned to an intervention group (quadriceps strengthening plus hip-abductor and lateral-rotator strengthening) or to a control group (quadriceps strengthening alone). No statistically significant differences between the groups before intervention.
The control group received/performed patellar mobilization; stretching of the quadriceps, gastrocnemius, iliotibial band, and hamstrings; and open kinetic chain and CKC quadriceps-strengthening exercises such as quad sets, straight-leg raises, minisquats, step-ups, and forward lunges. In addition to the above, the intervention group performed strengthening and functional training exercises for the transversus abdominis (TA) muscle, hip abductors, and lateral rotator muscles, such as side-lying hip abduction with external rotation and TA contraction in quadruped. All patients performed the rehabilitation exercises once per week under supervision and 4×/wk at home for 6 wk.
Study design
Participants
Interventions investigated
Nakagawa et al1
Table 2 Characteristics of Included Studies
32 subjects (M = 9, F = 23) with a mean age of 21 y (range 18–30) and a clinical diagnosis of unilateral PFPS. Randomly assigned to a closed kinetic chain (CKC) group or a CKC with hip muscles strengthening exercises (CKCH). No statistically significant differences between the groups before intervention.
54 women, sedentary for the past 6 mo, with a mean age of 23 y (range 20–40) and a clinical diagnosis of unilateral PFPS. Randomly assigned to a KE or a KHE group (KHE). No statistically significant differences between the groups before intervention.
The KE group performed stretching exercises (hamstrings, ankle plantar flexors, quadriceps, and iliotibial band) and strengthening of the knee musculature, such as seated knee extension, minisquats and leg press, single-leg calf raises, and prone knee flexion. The KHE group followed the same protocol but also performed exercises to strengthen the hip abductor, lateral rotator, and extensor muscles, such as side-lying hip abduction, hip-extension machine, and side-lying hip external rotation. The training load was standardized to 70% of the estimated 1RM. Exercises using elastic resistance were standardized to the maximum resistance at which each patient could perform 10 repetitions of the exercise. After the 4-wk treatment program, the patients were instructed to maintain their normal daily activities. The exercise groups completed 12 sessions 3×/wk for 4 wk.
70 women, sedentary for the past 6 m, with a mean age of 25 y (range 20–40) and a clinical diagnosis of unilateral PFPS. Randomly assigned to a knee-exercise group (KE), a knee- and hip-exercise group (KHE), a nontreatment group (control). No statistically significant differences between the groups before intervention. The KE group performed stretching exercises (hamstrings, ankle plantar flexors, quadriceps, and iliotibial band) and strengthening of the knee musculature, such as seated knee extension, minisquats and leg press, single-leg calf raises, and prone knee flexion. The KHE group followed the same protocol but also performed exercises to strengthen the posterolateral hip musculature, such as side-lying hip abduction and side-lying hip external rotation. The training load was standardized to 70% of the estimated 1-repetition maximum (1RM). Exercises using elastic resistance were standardized to the maximum resistance at which each patient could perform 10 repetitions of the exercise. After the 4-wk treatment program, patients were instructed to maintain their normal daily activities. The control group did not receive any form of treatment. The exercise groups completed 12 sessions 3×/wk for 4 wk.
(continued)
Both groups performed CKC exercises to strengthen the quadriceps, including mini-wall squats, forward step-ups, lateral step-ups, and terminal knee extension, in addition to stretching of the hamstrings, iliotibial band, gastrocnemius, and quadriceps. The CKCH group also performed resistive exercises for the hip abductors and external rotators. Each patient was trained at 60% of 10RM, and a new 10RM was established weekly as patients progressed. Both groups exercised 3×/wk for 6 wk.
Randomized controlled trial
Ismail et al4
Randomized controlled trial
Fukuda et al3
Randomized controlled trial
Fukuda et al2
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Pain (visual analog scale [VAS]) and function (pain during functional activities such as squatting and stair navigation), surface EMG activity of gluteus medius, and isokinetic eccentric knee-extensor, hip-abductor, and lateral-rotator torques pre- and postintervention.
After 6 wk of training, the intervention group (quads + hips) had significant improvements in pain during functional activities and in their gluteus medius electromyographic activity during isometric voluntary contraction (P < .05). Eccentric knee-extensor torque increased in both groups (P < .05). There was no statistically significant difference in hip-muscle torque in either group. The effect sizes for pain and function were 0.58 and 0.50, respectively.
1b
7/10
6 wk of quadriceps exercise plus strengthening of hip-abductor and lateral-rotator muscles resulted in greater improvements in pain and function than quadriceps strengthening alone in patients with PFPS.
Outcome measure(s)
Main findings
Level of evidence
PEDro score
Conclusion
8/10 Adding hip-strengthening exercises to a CKC knee-strengthening exercise protocol was more effective than knee-strengthening exercise alone in improving pain and function in patients with PFPS, although increases in hip torque from the training were similar between groups.
8/10 Knee stretching and strengthening exercises supplemented by hip-strengthening exercises were more effective than knee exercises alone in improving long-term function and reducing pain in sedentary women with PFPS.
1b
7/10
1b
After 6 wk of training, both groups had significant improvements in pain, function, and hip-muscle peak torque (P < .05) with no statistically significant difference between groups in hip-abductor and external-rotator torque (P < .05). Pain and functional improvements were significantly greater in the CKCH group (P < .05). The effect sizes for pain and function were 0.39 and 0.37, respectively.
Pain (VAS), function (Kujala questionnaire), and hip-abductor and external-rotator concentric/eccentric isokinetic torque before and after treatment.
Randomized controlled trial
Ismail et al4
Supplementing knee strengthening and stretching exercises with hip strengthening resulted in greater improvements in pain and function than knee strengthening alone in patients with PFPS.
1b
The effect sizes for pain and function were 0.28 and 0.25, respectively.
The KHE group had significant improvements in function and pain at 3, 6, and 12 mo compared with baseline (P < .05), while the KE group had reduced pain only at the 3- and 6-mo follow-ups (P < .05) and no improvements in LEFS, AKPS, or hop testing (P > .05). The KHE group had less pain and better function at 3, 6, and 12 mo posttreatment than the KE group (P < .05). The effect sizes for pain and function were 0.86 and 0.81, respectively.
Pain (NPRS), function (LEFS and AKPS), and a single-hop test were assessed at baseline and 3, 6, and 12 mo posttreatment.
Pain (Numeric Pain Rating Scale [NPRS] and Anterior Knee Pain Scale [AKPS]), function (Lower Extremity Functional Scale [LEFS]), and a single-hop test.
After 4 wk of training, the KE and KHE groups both showed significant improvement in LEFS, AKPS, and NPRS compared with the control group (P < .05). Given the MCID for the AKPS and NPRS, however, only the KHE group had mean improvements in these measures that were large enough to be clinically meaningful. For the single-limb single-hop test, the KE and KHE groups showed greater improvement than the control group, but there was no difference between the KE and KHE groups.
Randomized controlled trial
Fukuda et al3
Randomized controlled trial
Fukuda et al2
Note: M indicates male; F, female; PFPS, patellofemoral pain syndrome; MCID, minimal clinically important difference.
Randomized controlled trial
Study design
Nakagawa et al1
Table 2 (continued)
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432 Bloomer and Durall
Figure 1 — Forest plot of the effect sizes for functional improvements of the reviewed articles.
Figure 2 — Forest plot of the effect sizes for pain improvements of the reviewed articles.
Notably, the other study in this review by Fukuda et al2 had the smallest between-groups effect sizes for pain and function. This was, however, the only study that also included a nonintervention control group. Both exercise groups demonstrated moderate improvements in pain and function compared with the control group. The effect sizes for the knee-focused group compared with the control group were 0.48 and 0.45 for function and pain, respectively. The effect sizes for the knee- plus hip-strengthening group compared with the control group were 0.49 and 0.54 for function and pain, respectively. This suggests that both exercise approaches are likely to produce clinically significant improvements in pain and function compared with no treatment.
Research on PFPS suggests that potential contributors to abnormal patellofemoral-joint stress include excessive hip adduction and/or hip internal-rotation excursions during weight-bearing activity, increased knee-abduction landing mechanics, shortened quadriceps muscles, an altered vastus medialis obliquus muscle-reflex response time, decreased explosive strength and jumping power, a hypermobile patella, and/or decreased hipextensor muscle endurance.1–10 Some researchers have recommended resistance exercise for the hip abductors, external rotators, and extensors to constrain excessive hip adduction and/or hip internal-rotation excursions during weight-bearing activity and consequently to reduce patellofemoral-joint stress.1–8 Dolak et al6 reported that a
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Hip Strengthening, Knee-Focused Exercise, and PFPS 433
hip-abductor and external-rotator-strengthening program was more beneficial than a quadriceps-strengthening program in reducing pain in patients with PFPS. In contrast, Song et al7 found that performing a leg-press exercise with isometric hip adduction, in an effort to recruit the hip-adductor muscles, was no more effective than an isolated leg-press exercise in improving pain and function in patients with PFPS. This suggests that recruitment of the hip-adductor muscles may be less important than the hip abductors and external rotators and extensors. Although some clinicians stress targeted training of the vastus medialis oblique to treat PFPS, data have shown that general quadriceps strengthening is just as effective.5,8 A systematic review by Peters and Tyson8 concluded that core-stabilizing exercises should also be included for patients with PFPS to reduce patellofemoraljoint loads via improved lumbopelvic stability. Due to the apparent benefits of hip strengthening for patients with PFPS, future research to evaluate the impacts of hip strengthening for some other common knee pathologies (eg, osteoarthritis, ligament sprains, tendinitis, bursitis) should be considered. Since the studies in this review included more females than males, researchers may want to study gender differences in outcomes when hip strengthening is included in the treatment of PFPS. In addition, future research would be useful to determine the effects of supplemental treatments such as manual therapy, modalities, patellar taping, bracing, and biofeedback in addition to the exercise approaches evaluated in this review. Future inquiry should also be directed toward determining the efficacy of hipextension strengthening for PFPS. Fukuda et al,3 the only investigators in this review who used a hip-extension machine, reported the largest improvements in pain and function. Additional studies, similar to that discussed herein by Dolak et al,6 are needed to compare outcomes after hip strengthening alone versus knee-focused exercise in patients with PFPS. This may help guide clinicians regarding exercise selection and prioritization in situations when certain exercises are not tolerated. Finally, since only 1 of the studies in this review included long-term follow-up,3 additional research is needed to study the long-term benefits of exercise interventions in patients with PFPS.
References 1. Nakagawa TH, Muniz TB, Baldon RM, Dias MC, de Menezes Reiff RB, Serrao FV. The effect of additional strengthening of hip abductor and lateral rotator muscles
in patellofemoral pain syndrome: a randomized controlled pilot study. Clin Rehabil. 2008;22(12):1051–1060. PubMed doi:10.1177/0269215508095357 2. Fukuda TY, Rossetto FM, Magalhães E, Bryk FF, Lucareli PR, de Almeida Aparecida Carvalho N. Short-term effects of hip abductors and lateral rotators strengthening in females with patellofemoral pain syndrome: a randomized controlled clinical trial. J Orthop Sports Phys Ther. 2010;40(11):736–742. 3. Fukuda TY, Melo WP, Zaffalon BM, et al. Hip posterolateral musculature strengthening in sedentary women with patellofemoral pain syndrome: a randomized controlled clinical trial with 1-year follow-up. J Orthop Sports Phys Ther. 2012;42(10):823–830. PubMed doi:10.2519/ jospt.2012.4184 4. Ismail MM, Gamaleldein MH, Hassa KA. Closed kinetic chain exercises with or without additional hip strengthening exercises in management of patellofemoral pain syndrome: a randomized controlled trial. Eur J Phys Rehabil Med. 2013;49(5):687–698. PubMed 5. Bolgla LA, Boling MC. An update for the conservative management of patellofemoral pain syndrome: a systematic review of the literature from 2000 to 2010. Int J Sports Phys Ther. 2011;6(2):112–125. PubMed 6. Dolak KL, Silkman C, Medina McKeon J, Hosey RG, Lattermann C, Uhl TL. Hip strengthening prior to functional exercises reduces pain sooner than quadriceps strengthening in females with patellofemoral pain syndrome: a randomized clinical trial. J Orthop Sports Phys Ther. 2011;41(8):560–570. PubMed doi:10.2519/ jospt.2011.3499 7. Song CY, Lin YF, Wei TC, Lin DH, Yen TY, Jan MH. Surplus value of hip adduction in leg-press exercise in patients with patellofemoral pain syndrome: a randomized controlled trial. Phys Ther. 2009;89(5):409–418. PubMed doi:10.2522/ptj.20080195 8. Peters JSJ, Tyson NL. Proximal exercises are effective in treating patellofemoral pain syndrome: a systematic review. Int J Sports Phys Ther. 2013;8(5):689–700. PubMed 9. Myer GD, Ford KR, Barber Foss KD, et al. The incidence and potential pathomechanics of patellofemoral pain in female athletes. Clin Biomech (Bristol, Avon). 2010;25(7):700–707. PubMed doi:10.1016/j.clinbiomech.2010.04.001 10. Witvrouw E, Lysens R, Bellemans J, Cambier D, Vanderstraeten G. Intrinsic risk factors for the development of anterior knee pain in an athletic population: a two-year prospective study. Am J Sports Med. 2000;28(4):480–489. PubMed
JSR Vol. 24, No. 4, 2015
CRITICALLY APPRAISED TOPIC
Does the Addition of Hip Strengthening to a Knee-Focused Exercise Program Improve Outcomes in Patients With Patellofemoral Pain Syndrome? Ben A. Bloomer and Chris J. Durall Clinical Scenario: Patellofemoral pain syndrome (PFPS) is one of the most common disorders affecting the lower extremities. To improve function and decrease pain, affected individuals often undergo a guided rehabilitation program. Traditional programs have concentrated on quadriceps strengthening and other knee-focused exercises, but recent literature suggests that adding hip-muscle strengthening may improve outcomes. This review was conducted to determine the extent to which current evidence supports the addition of hip-muscle strengthening to a knee-focused strengthening and stretching program in the treatment of PFPS. Focused Clinical Question: Does the addition of hip-muscle strengthening to a knee-focused strengthening and stretching program improve outcomes in patients with PFPS? Keywords: patella, rehabilitation, resistance training
Clinical Scenario Patellofemoral pain syndrome (PFPS) is one of the most common disorders affecting the lower extremities.1–8 To improve function and decrease pain, affected individuals often undergo a guided rehabilitation program. Traditional programs have concentrated on quadriceps strengthening and other knee-focused exercises, but recent literature suggests that adding hip-muscle strengthening may improve outcomes.1–8 This review was conducted to determine the extent to which current evidence supports the addition of hip-muscle strengthening to a knee-focused strengthening and stretching program in the treatment of PFPS.
Focused Clinical Question Does the addition of hip-muscle strengthening to a kneefocused strengthening and stretching program improve outcomes in patients with PFPS?
Summary of Search, “Best Evidence” Appraised, and Key Findings The literature was searched for studies that directly compared knee-focused exercise (strengthening and stretching) combined with hip strengthening with The authors are with the Doctor of Physical Therapy Program, University of Wisconsin–La Crosse, La Crosse, WI. Address author correspondence to Ben Bloomer at benbloomer8@ gmail.com. 428
knee-focused exercise alone in the management of PFPS. The search yielded 4 level 1b randomized controlled trials (RCTs) that directly compared pain and functional outcomes between these 2 exercise interventions. In all 4 of the reviewed studies, the addition of hip-muscle strengthening to a knee-focused exercise program resulted in superior outcomes in pain and function.
Clinical Bottom Line Current high-quality evidence supports the addition of hip-muscle strengthening to knee-focused strengthening and stretching for individuals with PFPS to help reduce pain and improve function. Based on the reviewed literature, clinicians should consider exercises for the hip abductors (eg, side-lying and standing hip abduction with TheraBand or ankle weights), external rotators (eg, seated external rotation with TheraBand), and extensor muscles (eg, hip-extension machines) when treating patients with PFPS.1–4 Clinicians should also use kneefocused strengthening exercises (eg, squats, lunges, quadriceps sets, step-ups, terminal knee extension) and stretching exercises for the hamstrings, iliotibial band, gastrocnemius, and quadriceps.1–4 For the strengthening exercises, 2 to 4 sets of 10 to 15 repetitions should be performed. The stretching exercises should be held for 30 seconds and performed 3 times consecutively a minimum of 3 times per week for 4 weeks.1–4 Strength of Recommendation: Level 1 evidence from 4 RCTs supports the addition of hip-muscle strengthening to a knee-focused strengthening and stretching program to improve pain and function in patients with PFPS. Although the statistical difference between the 5 exercise interventions (knee-focused vs
Hip Strengthening, Knee-Focused Exercise, and PFPS 429
hip plus knee) was significant in all 4 studies, the effect size in 3 of the studies was small, suggesting that the clinical difference between the 2 approaches may be somewhat nominal.
Search Strategy Terms Used to Guide Search Strategy
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• Patient/Client group: subjects and patellofemoral pain syndrome • Intervention/Assessment: hip strengthening and knee-focused strengthening and stretching • Comparison: knee-focused strengthening and stretching alone • Outcome(s): pain and function
Sources of Evidence Searched • PubMed • CINAHL Plus • SPORTDiscus • MEDLINE • Alt HealthWatch • EBSCOhost • Cochrane Database of Systematic Reviews • PsycINFO • Additional resources obtained via manual search of reference lists
Inclusion and Ex9clusion Criteria Inclusion Criteria • At least 2 clinical signs of PFPS (anterior or retropatellar knee pain during ascending/descending stairs, squatting, running, kneeling, hopping/ jumping, and prolonged sitting) • Insidious onset of knee pain unrelated to trauma and persistent for at least 4 weeks • Studies that compared knee-focused exercises with knee-focused exercises plus hip-muscle strengthening • Limited to humans • Limited to English language • Limited to the last 10 years (2005–2014)
Exclusion Criteria • Participants with other concomitant pathological conditions of the knee or hip (eg, meniscus or ligamentous involvement, arthritis) or previous knee or hip surgery. • Studies that only compared knee-focused exercises with hip-muscle strengthening.
Results of Search Many relevant studies were retrieved, but only 4 studies that met eligibility requirements1–4 were selected for review. These are summarized in Table 1. All 4 studies directly compared knee-focused exercises alone with knee-focused exercises combined with hip-muscle strengthening to address PFPS.
Best Evidence The studies in Table 2 were identified as the best evidence for this review. All 4 articles were level 1b evidence RCTs based on Centre for Evidence-Based Medicine 2009 criteria.
Implications for Practice, Education, and Future Research In each of the 4 reviewed studies, patients with PFPS demonstrated statistically significant improvements in pain and function in response to either a knee-focused exercise program or a combined knee- and hip-musclestrengthening program.1–4 However, the improvements were significantly greater in the groups that performed hip-strengthening exercises. The pooled effect sizes of the 4 studies were 0.53 and 0.48 for pain and function, respectively (Figures 1 and 2), suggesting that clinical differences between these exercise approaches may be somewhat modest. It is worth noting, however, that the 1 study (Fukuda et al3) with a large effect size (>0.80 for pain and function) was also the only study with long-term follow-ups. In that study, Fukuda et al3 reported that both groups improved at the 3- and 6-month follow-ups, but only the hip-plus-knee-exercise group demonstrated improvements at the 12-month follow-up. The other 3 studies examined in this review, which had shorter follow-up periods (4 or 6 wk), had smaller betweengroups effect sizes for pain and function. Thus, additional data are needed to ascertain if differences in outcomes between the 2 exercise approaches are more pronounced in the long term. Fukuda et al3 was also the only study in which participants used a hip-extension machine, suggesting that hip-extensor exercise may be particularly beneficial for individuals with PFPS. It is also plausible that larger samples may yield larger between-groups effect sizes in the short term. Table 1 Summary of Study Designs of Retrieved Articles Level of evidence
Study design
Number located
Reference
1b
RCT
4
Nakagawa et al1
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Fukuda et al2 Fukuda et al3 Ismail et al4
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Randomized controlled trial
14 patients (M = 4, F = 10) with a mean age of 24 y (range 17–40) clinically diagnosed with PFPS and randomly assigned to an intervention group (quadriceps strengthening plus hip-abductor and lateral-rotator strengthening) or to a control group (quadriceps strengthening alone). No statistically significant differences between the groups before intervention.
The control group received/performed patellar mobilization; stretching of the quadriceps, gastrocnemius, iliotibial band, and hamstrings; and open kinetic chain and CKC quadriceps-strengthening exercises such as quad sets, straight-leg raises, minisquats, step-ups, and forward lunges. In addition to the above, the intervention group performed strengthening and functional training exercises for the transversus abdominis (TA) muscle, hip abductors, and lateral rotator muscles, such as side-lying hip abduction with external rotation and TA contraction in quadruped. All patients performed the rehabilitation exercises once per week under supervision and 4×/wk at home for 6 wk.
Study design
Participants
Interventions investigated
Nakagawa et al1
Table 2 Characteristics of Included Studies
32 subjects (M = 9, F = 23) with a mean age of 21 y (range 18–30) and a clinical diagnosis of unilateral PFPS. Randomly assigned to a closed kinetic chain (CKC) group or a CKC with hip muscles strengthening exercises (CKCH). No statistically significant differences between the groups before intervention.
54 women, sedentary for the past 6 mo, with a mean age of 23 y (range 20–40) and a clinical diagnosis of unilateral PFPS. Randomly assigned to a KE or a KHE group (KHE). No statistically significant differences between the groups before intervention.
The KE group performed stretching exercises (hamstrings, ankle plantar flexors, quadriceps, and iliotibial band) and strengthening of the knee musculature, such as seated knee extension, minisquats and leg press, single-leg calf raises, and prone knee flexion. The KHE group followed the same protocol but also performed exercises to strengthen the hip abductor, lateral rotator, and extensor muscles, such as side-lying hip abduction, hip-extension machine, and side-lying hip external rotation. The training load was standardized to 70% of the estimated 1RM. Exercises using elastic resistance were standardized to the maximum resistance at which each patient could perform 10 repetitions of the exercise. After the 4-wk treatment program, the patients were instructed to maintain their normal daily activities. The exercise groups completed 12 sessions 3×/wk for 4 wk.
70 women, sedentary for the past 6 m, with a mean age of 25 y (range 20–40) and a clinical diagnosis of unilateral PFPS. Randomly assigned to a knee-exercise group (KE), a knee- and hip-exercise group (KHE), a nontreatment group (control). No statistically significant differences between the groups before intervention. The KE group performed stretching exercises (hamstrings, ankle plantar flexors, quadriceps, and iliotibial band) and strengthening of the knee musculature, such as seated knee extension, minisquats and leg press, single-leg calf raises, and prone knee flexion. The KHE group followed the same protocol but also performed exercises to strengthen the posterolateral hip musculature, such as side-lying hip abduction and side-lying hip external rotation. The training load was standardized to 70% of the estimated 1-repetition maximum (1RM). Exercises using elastic resistance were standardized to the maximum resistance at which each patient could perform 10 repetitions of the exercise. After the 4-wk treatment program, patients were instructed to maintain their normal daily activities. The control group did not receive any form of treatment. The exercise groups completed 12 sessions 3×/wk for 4 wk.
(continued)
Both groups performed CKC exercises to strengthen the quadriceps, including mini-wall squats, forward step-ups, lateral step-ups, and terminal knee extension, in addition to stretching of the hamstrings, iliotibial band, gastrocnemius, and quadriceps. The CKCH group also performed resistive exercises for the hip abductors and external rotators. Each patient was trained at 60% of 10RM, and a new 10RM was established weekly as patients progressed. Both groups exercised 3×/wk for 6 wk.
Randomized controlled trial
Ismail et al4
Randomized controlled trial
Fukuda et al3
Randomized controlled trial
Fukuda et al2
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431
Pain (visual analog scale [VAS]) and function (pain during functional activities such as squatting and stair navigation), surface EMG activity of gluteus medius, and isokinetic eccentric knee-extensor, hip-abductor, and lateral-rotator torques pre- and postintervention.
After 6 wk of training, the intervention group (quads + hips) had significant improvements in pain during functional activities and in their gluteus medius electromyographic activity during isometric voluntary contraction (P < .05). Eccentric knee-extensor torque increased in both groups (P < .05). There was no statistically significant difference in hip-muscle torque in either group. The effect sizes for pain and function were 0.58 and 0.50, respectively.
1b
7/10
6 wk of quadriceps exercise plus strengthening of hip-abductor and lateral-rotator muscles resulted in greater improvements in pain and function than quadriceps strengthening alone in patients with PFPS.
Outcome measure(s)
Main findings
Level of evidence
PEDro score
Conclusion
8/10 Adding hip-strengthening exercises to a CKC knee-strengthening exercise protocol was more effective than knee-strengthening exercise alone in improving pain and function in patients with PFPS, although increases in hip torque from the training were similar between groups.
8/10 Knee stretching and strengthening exercises supplemented by hip-strengthening exercises were more effective than knee exercises alone in improving long-term function and reducing pain in sedentary women with PFPS.
1b
7/10
1b
After 6 wk of training, both groups had significant improvements in pain, function, and hip-muscle peak torque (P < .05) with no statistically significant difference between groups in hip-abductor and external-rotator torque (P < .05). Pain and functional improvements were significantly greater in the CKCH group (P < .05). The effect sizes for pain and function were 0.39 and 0.37, respectively.
Pain (VAS), function (Kujala questionnaire), and hip-abductor and external-rotator concentric/eccentric isokinetic torque before and after treatment.
Randomized controlled trial
Ismail et al4
Supplementing knee strengthening and stretching exercises with hip strengthening resulted in greater improvements in pain and function than knee strengthening alone in patients with PFPS.
1b
The effect sizes for pain and function were 0.28 and 0.25, respectively.
The KHE group had significant improvements in function and pain at 3, 6, and 12 mo compared with baseline (P < .05), while the KE group had reduced pain only at the 3- and 6-mo follow-ups (P < .05) and no improvements in LEFS, AKPS, or hop testing (P > .05). The KHE group had less pain and better function at 3, 6, and 12 mo posttreatment than the KE group (P < .05). The effect sizes for pain and function were 0.86 and 0.81, respectively.
Pain (NPRS), function (LEFS and AKPS), and a single-hop test were assessed at baseline and 3, 6, and 12 mo posttreatment.
Pain (Numeric Pain Rating Scale [NPRS] and Anterior Knee Pain Scale [AKPS]), function (Lower Extremity Functional Scale [LEFS]), and a single-hop test.
After 4 wk of training, the KE and KHE groups both showed significant improvement in LEFS, AKPS, and NPRS compared with the control group (P < .05). Given the MCID for the AKPS and NPRS, however, only the KHE group had mean improvements in these measures that were large enough to be clinically meaningful. For the single-limb single-hop test, the KE and KHE groups showed greater improvement than the control group, but there was no difference between the KE and KHE groups.
Randomized controlled trial
Fukuda et al3
Randomized controlled trial
Fukuda et al2
Note: M indicates male; F, female; PFPS, patellofemoral pain syndrome; MCID, minimal clinically important difference.
Randomized controlled trial
Study design
Nakagawa et al1
Table 2 (continued)
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432 Bloomer and Durall
Figure 1 — Forest plot of the effect sizes for functional improvements of the reviewed articles.
Figure 2 — Forest plot of the effect sizes for pain improvements of the reviewed articles.
Notably, the other study in this review by Fukuda et al2 had the smallest between-groups effect sizes for pain and function. This was, however, the only study that also included a nonintervention control group. Both exercise groups demonstrated moderate improvements in pain and function compared with the control group. The effect sizes for the knee-focused group compared with the control group were 0.48 and 0.45 for function and pain, respectively. The effect sizes for the knee- plus hip-strengthening group compared with the control group were 0.49 and 0.54 for function and pain, respectively. This suggests that both exercise approaches are likely to produce clinically significant improvements in pain and function compared with no treatment.
Research on PFPS suggests that potential contributors to abnormal patellofemoral-joint stress include excessive hip adduction and/or hip internal-rotation excursions during weight-bearing activity, increased knee-abduction landing mechanics, shortened quadriceps muscles, an altered vastus medialis obliquus muscle-reflex response time, decreased explosive strength and jumping power, a hypermobile patella, and/or decreased hipextensor muscle endurance.1–10 Some researchers have recommended resistance exercise for the hip abductors, external rotators, and extensors to constrain excessive hip adduction and/or hip internal-rotation excursions during weight-bearing activity and consequently to reduce patellofemoral-joint stress.1–8 Dolak et al6 reported that a
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Hip Strengthening, Knee-Focused Exercise, and PFPS 433
hip-abductor and external-rotator-strengthening program was more beneficial than a quadriceps-strengthening program in reducing pain in patients with PFPS. In contrast, Song et al7 found that performing a leg-press exercise with isometric hip adduction, in an effort to recruit the hip-adductor muscles, was no more effective than an isolated leg-press exercise in improving pain and function in patients with PFPS. This suggests that recruitment of the hip-adductor muscles may be less important than the hip abductors and external rotators and extensors. Although some clinicians stress targeted training of the vastus medialis oblique to treat PFPS, data have shown that general quadriceps strengthening is just as effective.5,8 A systematic review by Peters and Tyson8 concluded that core-stabilizing exercises should also be included for patients with PFPS to reduce patellofemoraljoint loads via improved lumbopelvic stability. Due to the apparent benefits of hip strengthening for patients with PFPS, future research to evaluate the impacts of hip strengthening for some other common knee pathologies (eg, osteoarthritis, ligament sprains, tendinitis, bursitis) should be considered. Since the studies in this review included more females than males, researchers may want to study gender differences in outcomes when hip strengthening is included in the treatment of PFPS. In addition, future research would be useful to determine the effects of supplemental treatments such as manual therapy, modalities, patellar taping, bracing, and biofeedback in addition to the exercise approaches evaluated in this review. Future inquiry should also be directed toward determining the efficacy of hipextension strengthening for PFPS. Fukuda et al,3 the only investigators in this review who used a hip-extension machine, reported the largest improvements in pain and function. Additional studies, similar to that discussed herein by Dolak et al,6 are needed to compare outcomes after hip strengthening alone versus knee-focused exercise in patients with PFPS. This may help guide clinicians regarding exercise selection and prioritization in situations when certain exercises are not tolerated. Finally, since only 1 of the studies in this review included long-term follow-up,3 additional research is needed to study the long-term benefits of exercise interventions in patients with PFPS.
References 1. Nakagawa TH, Muniz TB, Baldon RM, Dias MC, de Menezes Reiff RB, Serrao FV. The effect of additional strengthening of hip abductor and lateral rotator muscles
in patellofemoral pain syndrome: a randomized controlled pilot study. Clin Rehabil. 2008;22(12):1051–1060. PubMed doi:10.1177/0269215508095357 2. Fukuda TY, Rossetto FM, Magalhães E, Bryk FF, Lucareli PR, de Almeida Aparecida Carvalho N. Short-term effects of hip abductors and lateral rotators strengthening in females with patellofemoral pain syndrome: a randomized controlled clinical trial. J Orthop Sports Phys Ther. 2010;40(11):736–742. 3. Fukuda TY, Melo WP, Zaffalon BM, et al. Hip posterolateral musculature strengthening in sedentary women with patellofemoral pain syndrome: a randomized controlled clinical trial with 1-year follow-up. J Orthop Sports Phys Ther. 2012;42(10):823–830. PubMed doi:10.2519/ jospt.2012.4184 4. Ismail MM, Gamaleldein MH, Hassa KA. Closed kinetic chain exercises with or without additional hip strengthening exercises in management of patellofemoral pain syndrome: a randomized controlled trial. Eur J Phys Rehabil Med. 2013;49(5):687–698. PubMed 5. Bolgla LA, Boling MC. An update for the conservative management of patellofemoral pain syndrome: a systematic review of the literature from 2000 to 2010. Int J Sports Phys Ther. 2011;6(2):112–125. PubMed 6. Dolak KL, Silkman C, Medina McKeon J, Hosey RG, Lattermann C, Uhl TL. Hip strengthening prior to functional exercises reduces pain sooner than quadriceps strengthening in females with patellofemoral pain syndrome: a randomized clinical trial. J Orthop Sports Phys Ther. 2011;41(8):560–570. PubMed doi:10.2519/ jospt.2011.3499 7. Song CY, Lin YF, Wei TC, Lin DH, Yen TY, Jan MH. Surplus value of hip adduction in leg-press exercise in patients with patellofemoral pain syndrome: a randomized controlled trial. Phys Ther. 2009;89(5):409–418. PubMed doi:10.2522/ptj.20080195 8. Peters JSJ, Tyson NL. Proximal exercises are effective in treating patellofemoral pain syndrome: a systematic review. Int J Sports Phys Ther. 2013;8(5):689–700. PubMed 9. Myer GD, Ford KR, Barber Foss KD, et al. The incidence and potential pathomechanics of patellofemoral pain in female athletes. Clin Biomech (Bristol, Avon). 2010;25(7):700–707. PubMed doi:10.1016/j.clinbiomech.2010.04.001 10. Witvrouw E, Lysens R, Bellemans J, Cambier D, Vanderstraeten G. Intrinsic risk factors for the development of anterior knee pain in an athletic population: a two-year prospective study. Am J Sports Med. 2000;28(4):480–489. PubMed
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