Karen D. Kendall

Changes in Knee Biomechanics After a Hip-Abductor Strengthening Protocol for Runners With Patellofemoral Pain Syndrome

CONTEXT Very few authors have investigated the relationship between hip-abductor muscle strength and frontal-plane knee mechanics during running. OBJECTIVE To investigate this relationship using a 3-week hip-abductor muscle-strengthening program to identify changes in strength, pain, and biomechanics in runners with patellofemoral pain syndrome (PFPS). DESIGN Cohort study. SETTING University-based clinical research laboratory. PATIENTS OR OTHER PARTICIPANTS Fifteen individuals (5 men, 10 women) with PFPS and 10 individuals without PFPS (4 men, 6 women) participated. INTERVENTION(S) The patients with PFPS completed a 3-week hip-abductor strengthening protocol; control participants did not. MAIN OUTCOME MEASURE(S) The dependent variables of interest were maximal isometric hip-abductor muscle strength, 2-dimensional peak knee genu valgum angle, and stride-to-stride knee-joint variability. All measures were recorded at baseline and 3 weeks later. Between-groups differences were compared using repeated-measures analyses of variance. RESULTS At baseline, the PFPS group exhibited reduced strength, no difference in peak genu valgum angle, and increased stride-to-stride knee-joint variability compared with the control group. After the 3-week protocol, the PFPS group demonstrated increased strength, less pain, no change in peak genu valgum angle, and reduced stride-to-stride knee-joint variability compared with baseline. CONCLUSIONS A 3-week hip-abductor muscle-strengthening protocol was effective in increasing muscle strength and decreasing pain and stride-to-stride knee-joint variability in individuals with PFPS. However, concomitant changes in peak knee genu valgum angle were not observed.

Suspected Mechanisms in the Cause of Overuse Running Injuries: A Clinical Review:

Context: Various epidemiological studies have estimated that up to 70% of runners sustain an overuse running injury each year. Although few overuse running injuries have an established cause, more than 80% of running-related injuries occur at or below the knee, which suggests that some common mechanisms may be at work. The question then becomes, are there common mechanisms related to overuse running injuries? Evidence Acquisition: Research studies were identified via the following electronic databases: MEDLINE, EMBASE PsycInfo, and CINAHL (1980–July 2008). Inclusion was based on evaluation of risk factors for overuse running injuries. Results: A majority of the risk factors that have been researched over the past few years can be generally categorized into 2 groups: atypical foot pronation mechanics and inadequate hip muscle stabilization. Conclusion: Based on the review of literature, there is no definitive link between atypical foot mechanics and running injury mechanisms. The lack of normative data and a definition of typical foot structure has hampered progress. In contrast, a large and growing body of literature suggests that weakness of hip-stabilizing muscles leads to atypical lower extremity mechanics and increased forces within the lower extremity while running.

Steps toward the validation of the Trendelenburg test: the effect of experimentally reduced hip abductor muscle function on frontal plane mechanics.

Objective:To investigate the validity of the Trendelenburg test (TT) using an ultrasound-guided nerve block (UNB) of the superior gluteal nerve and determine whether the reduction in hip abductor muscle (HABD) strength would result in the theorized mechanical compensatory strategies measured during the TT. Design:Quasi-experimental. Setting:Hospital. Participants:Convenience sample of 9 healthy men. Only participants with no current or previous injury to the lumbar spine, pelvis, or lower extremities, and no previous surgeries were included. Interventions:Ultrasound-guided nerve block. Main Outcome Measures:Hip abductor muscle strength (percent body weight [%BW]), contralateral pelvic drop (cPD), change in contralateral pelvic drop (&Dgr;cPD), ipsilateral hip adduction, and ipsilateral trunk sway (TRUNK) measured in degrees. Results:The median age and weight of the participants were 31 years (interquartile range [IQR], 22-32 years) and 73 kg (IQR, 67-81 kg), respectively. An average 52% reduction of HABD strength (z = 2.36, P = 0.02) resulted after the UNB. No differences were found in cPD or &Dgr;cPD (z = 0.01, P = 0.99, z = −0.67, P = 0.49, respectively). Individual changes in biomechanics showed no consistency between participants and nonsystematic changes across the group. One participant demonstrated the mechanical compensations described by Trendelenburg. Conclusions:The TT should not be used as a screening measure for HABD strength in populations demonstrating strength greater than 30%BW but should be reserved for use with populations with marked HABD weakness. Clinical Relevance:This study presents data regarding a critical level of HABD strength required to support the pelvis during the TT.

The effect of the addition of hip strengthening exercises to a lumbopelvic exercise programme for the treatment of non-specific low back pain: A randomized controlled trial

OBJECTIVES To compare the efficacy of two exercise programmes in reducing pain and disability for individuals with non-specific low back pain and to examine the underlying mechanical factors related to pain and disability for individuals with NSLBP. DESIGN A single-blind, randomized controlled trial. METHODS Eighty participants were recruited from eleven community-based general medical practices and randomized into two groups completing either a lumbopelvic motor control or a combined lumbopelvic motor control and progressive hip strengthening exercise therapy programme. All participants received an education session, 6 rehabilitation sessions including real time ultrasound training, and a home based exercise programme manual and log book. The primary outcomes were pain (0-100 mm visual analogue scale), and disability (Oswestry Disability Index V2). The secondary outcomes were hip strength (N/kg) and two-dimensional frontal plane biomechanics (°) measure during the static Trendelenburg test and while walking. All outcomes were measured at baseline and at 6-week follow up. RESULTS There was no statistical difference in the change in pain (x¯ = -4.0 mm, t = -1.07, p = 0.29, 95%CI -11.5, 3.5) or disability (x¯ = -0.3%, t = -0.19, p = 0.85, 95%CI -3.5, 2.8) between groups. Within group comparisons revealed clinically meaningful reductions in pain for both Group One (x¯ = -20.9 mm, 95%CI -25.7, -16.1) and Group Two (x¯ = -24.9, 95%CI -30.8, -19.0). CONCLUSIONS Both exercise programmes had similar efficacy in reducing pain. The addition of hip strengthening exercises to a motor control exercise programme does not appear to result in improved clinical outcome for pain for individuals with non-specific low back pain.

Experimentally reduced hip-abductor muscle strength and frontal-plane biomechanics during walking.

CONTEXT Researchers have postulated that reduced hip-abductor muscle strength may have a role in the progression of knee osteoarthritis by increasing the external knee-adduction moment. However, the relationship between hip-abductor strength and frontal-plane biomechanics remains unclear. OBJECTIVE To experimentally reduce hip-abduction strength and observe the subsequent changes in frontal-plane biomechanics. DESIGN Descriptive laboratory study. SETTING Research laboratory. PATIENTS OR OTHER PARTICIPANTS Eight healthy, recreationally active men (age = 27 ± 6 years, height = 1.75 ± 0.11 m, mass = 76.1 ± 10.0 kg). INTERVENTION(S) All participants underwent a superior gluteal nerve block injection to reduce the force output of the hip-abductor muscle group. MAIN OUTCOME MEASURE(S) Maximal isometric hip-abduction strength and gait biomechanical data were collected before and after the injections. Gait biomechanical variables collected during walking consisted of knee- and hip-adduction moments and impulses and the peak angles of contralateral pelvic drop, hip adduction, and ipsilateral trunk lean. RESULTS Hip-abduction strength was reduced after the injection (P = .001) and remained lower than baseline values at the completion of the postinjection gait data collection (P = .02). No alterations in hip- or knee-adduction moments (hip: P = .11; knee: P = .52) or impulses (hip: P = .16; knee: P = .41) were found after the nerve block. Similarly, no changes in angular kinematics were observed for contralateral pelvic drop (P = .53), ipsilateral trunk lean (P = .78), or hip adduction (P = .48). CONCLUSIONS A short-term reduction in hip-abductor strength was not associated with alterations in the frontal-plane gait biomechanics of young, healthy men. Further research is needed to determine whether a similar relationship is true in older adults with knee osteoarthritis.