Can local muscles augment stability in the hip? A narrative literature review.

Hip pain and dysfunction are increasingly recognised as important causes of morbidity in younger and older adults. Pathology compromising the passive stability of the hip joint, including acetabular labral injury, may lead to increased femoral head translation, greater joint contact pressures and ultimately degenerative hip disease. Activation of hip muscles may play an important role in augmenting the stability in the normal and the passively unstable hip. Research at other joints suggests that the local, rather than global, muscles are well suited to provide subtle joint compression, limiting translation, with minimal metabolic cost. Based on the known characteristics of local muscles and the limited research available on hip muscles, it is proposed that the local hip muscles; quadratus femoris, gluteus minimus, gemelli, obturator internus and externus, iliocapsularis and the deep fibres of iliopsoas, may be primary stabilisers of the hip joint. Interventions aimed at restoring isolated neuromuscular function of the primary hip stabilisers may be considered when treating people with passive hip instability prior to commencing global muscle rehabilitation. Finally, further research is needed to investigate the potential association between function of the hip muscles (including muscles likely to have a role in stabilising the hip) and hip pathology affecting hip stability such as acetabular labral lesions.

Triceps surae activation is altered in male runners with Achilles tendinopathy.

UNLABELLED: Achilles tendinopathy is a common injury in running sports however the exact etiology of Achilles injury is still unclear. In recent years, altered neuromotor recruitment patterns of the triceps surae have been hypothesized to create differential intra-tendinous loads leading to pathology; however, this hypothesis has not been investigated. Further, the effect foot orthoses may have on neuromotor recruitment of the triceps surae in Achilles tendinopathy has not been investigated. METHODS: The electromyographic activity of the triceps surae was recorded during an over-ground running task. Fifteen Achilles injured participants and 19 asymptomatic controls were assessed in a footwear only condition. The Achilles injured participants were also assessed running in a pre-fabricated foot orthoses. RESULTS: In Achilles injured participants, there was a significant difference between soleus and lateral gastrocnemius offset times during running compared to the asymptomatic controls (p<0.05). There were no significant differences in triceps surae muscle activity between the footwear only and footwear and orthoses condition in the Achilles injured participants. CONCLUSIONS: The finding that triceps surae activity is altered in participants with Achilles tendinopathy may have clinical importance as it suggests that intra-tendinous loads are altered which may contribute to pathological changes. Further, foot orthoses have no immediate effect on the neuromotor control of the triceps surae.

Altered hip and trunk muscle function in individuals with patellofemoral pain.

OBJECTIVE: The purpose of this study was to investigate the role of hip muscles in patellofemoral pain (PFP), specifically by investigating neuromotor control, strength and range of motion of the hip muscles. DESIGN: Cross-sectional. SETTING: University laboratory. PATIENTS: Ten participants diagnosed with PFP and 27 asymptomatic controls were recruited, using standard inclusion and exclusion criteria. MAIN OUTCOME MEASURES: Electromyographic activity of the vasti and anterior gluteus medius (GM) were recorded using surface electrodes and posterior GM using fine wire electrodes while the participant completed a stair-stepping task. Hip strength and trunk side flexion strength was assessed using a hand-held dynamometer and hip range of motion with an inclinometer. Pain and disability measures were recorded for the PFP participants. RESULTS: When individuals with PFP completed the stair-stepping task there was a delay in activation of both anterior and posterior GM (p<0.02) and an alteration in vasti control (p = 0.001). In addition, trunk side flexion strength was significantly less (29%) in individuals with PFP (p = 0.03). CONCLUSION: This study provides evidence that trunk side flexion strength and neuromotor control of the GM are affected in people with PFP. This study also confirms the presence of a delayed vastus medialis obliquus relative to vastus lateralis, providing further evidence underpinning the importance of retraining the vasti function in patients with PFP.

Patellar taping does not change the amplitude of electromyographic activity of the vasti in a stair stepping task.

OBJECTIVES: To investigate the effect of patellar taping on the amplitude of electromyographic activity (EMG) of vasti activation in subjects with and without patellofemoral pain (PFP). METHODS: Ten participants with PFP and 12 asymptomatic controls were recruited to the study. The study was designed as a randomised crossover trial. Participants completed a stair stepping task. Three experimental conditions were assessed: no tape, therapeutic medially directed tape, and placebo vertically directed tape. The main outcome measure was the EMG amplitude of the vastus medialis obliquus and vastus lateralis during the concentric phase of stair stepping. RESULTS: The application of medially directed therapeutic tape significantly decreased pain in subjects with PFP. However, application of tape over the patella (therapeutic or placebo) did not alter the amplitude of vasti EMG when either the PFP or control participants completed the concentric stair stepping task. CONCLUSION: The results of this study indicate that the positive clinical effects of medially directed therapeutic tape are not due to changes in EMG amplitude of the vasti muscle. Thus other effects such as changes in timing of contraction of the vasti are more likely candidates for the mechanism of efficacy.

Delayed onset of electromyographic activity of vastus medialis obliquus relative to vastus lateralis in subjects with patellofemoral pain syndrome.

OBJECTIVE: To determine whether electromyographic (EMG) onsets of vastus medialis obliquus (VMO) and vastus lateralis (VL) are altered in the presence of patellofemoral pain syndrome (PFPS) during the functional task of stair stepping. DESIGN: Cross-sectional. SETTING: University laboratory. PATIENTS: Thirty-three subjects with PFPS and 33 asymptomatic controls. INTERVENTIONS: Subjects ascended and descended a set of stairs-2 steps, each 20-cm high-at usual stair-stepping pace. EMG readings of VMO and VL taken on middle stair during step up (concentric contraction) and step down (eccentric contraction). MAIN OUTCOME MEASURES: Relative difference in onset of surface EMG activity of VMO compared with VL during a stair-stepping task. EMG onsets were determined by using a computer algorithm and were verified visually. RESULTS: In the PFPS population, the EMG onset of VL occurred before that of VMO in both the step up and step down phases of the stair-stepping task (p <.05). In contrast, no such differences occurred in the onsets of EMG activity of VMO and VL in either phase of the task for the control subjects. CONCLUSION: This finding supports the hypothesized relationship between changes in the timing of activity of the vastimuscles and PFPS. This finding provides theoretical rationale to support physiotherapy treatment commonly used in the management of PFPS.

Patellar taping: is clinical success supported by scientific evidence?

Patellofemoral pain syndrome (PFPS) is a common condition presenting to physiotherapy and sports medicine practices. Despite its prevalence, the aetiology, pathogenesis, and recommended treatment remain unclear. One component of treatment for PFPS that has been subjected to scrutiny is patellar taping. This taping was designed to realign the patella within the femoral trochlea, thus reducing pain from PFPS and improving both quadriceps and patellofemoral joint function. Clinical and research findings confirm that the pain associated with PFPS is significantly reduced with patellar taping. Therefore, research has aimed at determining the mechanisms of this pain relief. The means by which patellar tape can relieve pain may provide insight into the aetiology and risk factors for PFPS, thus allowing more appropriately designed treatment regimes and preventative strategies. There is evidence to suggest that patellar tape improves patella alignment (measured radiographically) and quadriceps function (torque production and extensor moments). Evidence that patellar tape enhances the activation of individual vastii (magnitude or timing) is limited in quality and quantity, which probably reflects the difficulties inherent in measuring this complex question. There is preliminary evidence for improved knee control during gait in association with patellar tape. This paper critically reviews the studies that have examined the effects of patellar taping and makes informed recommendations for further research and clinical practice.

Metal-ion stoichiometry of the HIV-1 RT ribonuclease H domain: evidence for two mutually exclusive sites leads to new mechanistic insights on metal-mediated hydrolysis in nucleic acid biochemistry.

Crystallographic studies of the Mn(2+)-doped RNase H domain of human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) have revealed two bound Mn2+ separated by approximately 4A and surrounded by a cluster of four conserved carboxylates. Escherichia coli RNase H is structurally similar to the RNase H domain of HIV-1 RT, but requires one divalent metal cation for its activity, implying either that the HIV-1 RT RNase H domain contrasts in its ability to bind two divalent metal ions, or that the crystallographic data reflect specific use of Mn2+ and/ or the doping technique employed. Metal binding stoichiometry has been determined for Mn2+ and the biologically more relevant Mg2+ cation by solution calorimetric studies of native and recombinant p66/p51 HIV-1 RT. Three Mn2+ ions bind to HIV-1 RT apo-enzyme: one at the DNA polymerase and two at the RNase H catalytic center, the latter being consistent with crystallographic results. However, only one Mg2+ ion is bound in the RNase H catalytic center. Several mechanistic implications arise from these results, including the possibility of mutually exclusive Mg2+ binding sites that might be occupied according to the specific reaction being catalyzed by the multifunctional RNase H domain. The occurrence of distinct binding stoichiometries for Mg2+ and Mn2+ to multifunctional enzymes has previously been reported.