Question:
In women with patellofemoral pain syndrome (PFPS), is an open-chain hip-strengthening program associated with more improvement than an open-chain quadriceps-strengthening program in preparation for weight-bearing or functional exercises?
Design:
Randomized (allocation concealed), blinded (outcome assessor during the initial testing session) controlled trial with four and eight-week follow-up.
Setting:
University of Kentucky Musculoskeletal Laboratory, Lexington, Kentucky.
Patients:
Thirty-three women who had a mean age of twenty-five years (range, sixteen to thirty-five years of age) and had PFPS (bilateral PFPS in sixteen patients). Inclusion criteria were anterior or retropatellar knee pain during at least two of the following: stair-climbing, hopping, running, squatting, kneeling, or prolonged sitting; insidious onset of symptoms not related to trauma; pain with compression of the patella; and pain on palpation of patellar facets. Exclusion criteria were symptoms present for <1 month, other knee pathology, knee surgery within the past year, history of patella dislocations or subluxations, or any substantial injury affecting the lower extremity. Twenty-seven women (82%) completed the randomized intervention and were available for assessment at four weeks, and twenty-six (79%) completed the eight-week follow-up.
Intervention:
Patients were allocated to an open-chain hip-strengthening program (n = 17) or an open-chain quadriceps-strengthening program (n = 16) for four weeks. Both groups participated in flexibility exercises three times (thirty seconds each time) before performing strengthening exercises. Strengthening exercises were performed one day per week with an investigator and two days per week at home. The hip-group exercises began with side-lying combination hip abduction and external rotation, standing hip abduction, and seated hip external rotation during the first week; standing and side-lying hip abduction and seated hip external rotation, all with 3% body weight, during the second week; side-lying hip abduction and seated hip external rotation with 5% body weight and quadruped hydrant (combined hip abduction and external rotation) during the third week; and side-lying hip abduction and seated hip external rotation with 7% body weight and quadruped hydrant with 3% body weight during the fourth week. The quadriceps group exercises began with quad sets, short-arc quads, and straight-leg raises during the first week; short-arc quads, straight-leg raises, and terminal knee extensions with 3% body weight in the second week; and those same exercises but with 5% body weight during the third week and 7% body weight during the fourth week. In both groups, each exercise was performed in three sets of ten repetitions. After the four weeks of strengthening exercises, patients in both groups continued with the same allocated exercises plus functional weight-bearing and balance exercises.
Main outcome measures:
The primary outcome measures were worst pain in the past week, assessed on a 10-point visual analog scale (0 = no pain, and 10 = worst possible pain), and function, assessed with the Lower Extremity Functional Scale (LEFS) (score range, 0 to 80, with higher scores indicating better function). Secondary outcome measures were isometric strength as measured with a handheld dynamometer for the hip abductors, hip external rotators, and knee extensors (average torque normalized to participant height and weight); and functional strength assessed by a step-down task.
Main results:
Analysis was by intention to treat. At four weeks, there was less pain in the hip group than in the quadriceps group (2.4 versus 4.1, p = 0.035). Function according to the LEFS was improved in both groups, with no significant difference between them. Hip abductor strength increased from baseline (5.2) in the hip group to 6.2 at four weeks and 6.6 at eight weeks (p = 0.001), while the quadriceps group showed no improvement (5.7, 5.5, and 6.2 at baseline, four weeks, and eight weeks, respectively, p = 0.9). The groups did not differ with regard to other outcome measures.
Conclusion:
In women with patellofemoral pain syndrome, an open-chain hip-strengthening program alleviated pain sooner and improved hip abductor strength more than open-chain exercises that were focused on the quadriceps.
In the trial by Dolak et al., the rationale is that hip strengthening is widely utilized in the treatment of PFPS with little supporting evidence. There are at least two reasons for this. First, separating hip exercises from knee exercises is difficult. Second, the measurement of muscle strength is less accurate as one approaches from the knee, to the hip, to the torso.
Some factors should be considered when evaluating this study. First, the authors chose non-weight-bearing exercises (at the knee), which limited the available exercises, and the exercises that were chosen, especially when done in isolation, are not mainstream. Second, the study included participants with bilateral symptoms; patients with bilateral and unilateral painful knees may be different. Third, the visual analog scale, used frequently as a valid method for assessing perceived pain in patients with PFPS, was hard to interpret in this study, as the question was about global pain, not pain specific to the knee. Also, the intraclass correlation coefficient of the visual analog scale was large, indicating low repeatability. Fourth, the finding of pain ranging from being present only after activities to severe symptoms affecting activities of daily living suggests that vastly different populations were represented in this small cohort.
Despite the limitations of this study, the authors have shown that strengthening of the lower extremity for patients with PFPS was able to increase functional performance and reduce self-reported pain after eight weeks. The take-home message of this study is that, especially in the first weeks of rehabilitation, exercises outside of the knee may be a more clinically efficient approach to reducing pain and improving function.