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Daniel H. Huffman, Brian G. Pietrosimone, Terry L. Grindstaff, Joseph M. Hart, Susan A. Saliba and Christopher D. Ingersoll

Context:

Motoneuron-pool facilitation after cryotherapy may be mediated by stimulation of thermoreceptors surrounding a joint. It is unknown whether menthol counterirritants, which also stimulate thermoreceptors, have the same effect on motoneuron-pool excitability (MNPE).

Objective:

To compare quadriceps MNPE after a menthol-counterirritant application to the anterior knee, a sham counterirritant application, and a control treatment in healthy subjects.

Design:

A blinded, randomized controlled laboratory study.

Setting:

Laboratory.

Participants:

Thirty healthy subjects (16 m, 14 f; 24.1 ± 3.9 y, 170.6 ± 11.4 cm, 72.1 ± 15.6 kg) with no history of lower extremity surgery volunteered for this study.

Intervention:

Two milliliters of menthol or sham counterirritant was applied to the anterior knee; control subjects received no intervention.

Main Outcome Measures:

The average vastus medialis normalized Hoffmann reflex (Hmax:Mmax ratio) was used to measure MNPE. Measurements were recorded at 5, 15, 25, and 35 minutes postintervention and compared with baseline measures.

Results:

Hmax:Mmax ratios for all groups significantly decreased over time (F 4,108 = 10.52, P < .001; menthol: baseline = .32 ± .20, 5 min = .29 ± .18, 15 min = .27 ± .18, 25 min = .28 ± .19, 35 min = .27 ± .18; sham: baseline = .46 ± .26, 5 min = .36 ± .20, 15 min = .35 ± .19, 25 min = .35 ± .20, 35 min = .34 ± .18; control: baseline = .48 ± .32, 5 min = .37 ± .27, 15 min = .37 ± .27, 25 min = .37 ± .29, 35 min = .35 ± .28). No significant Group × Time interaction or group differences in Hmax:Mmax were found.

Conclusions:

Menthol did not affect quadriceps MNPE in healthy subjects.

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Lindsey K. Lepley, Abbey C. Thomas, Scott G. McLean and Riann M. Palmieri-Smith

Context:

As individuals returning to activity after anterior cruciate ligament reconstruction (ACLr) likely experience fatigue, understanding how fatigue affects knee-muscle activation patterns during sport-like maneuvers is of clinical importance. Fatigue has been suggested to impair neuromuscular control strategies. As a result, fatigue may place ACLr patients at increased risk of developing posttraumatic osteoarthritis (OA).

Objective:

To determine the effects of fatigue on knee-muscle activity post-ACLr.

Design:

Case control.

Setting:

University laboratory.

Participants:

12 individuals 7–10 mo post-ACLr (7 male, 5 female; age 22.1 ± 4.7 y; 1.8 ± 0.1 m; mass 77.7 ± 11.9 kg) and 13 controls (4 male, 9 female; age 22.9 ± 4.3 y; 1.7 ± 0.1 m; mass 66.9 ± 9.8 kg).

Interventions:

Fatigue was induced via repetitive sets of double-leg squats (n = 8), which were interspersed with sets of single-leg landings (n = 3), until squats were no longer possible.

Main Outcome Measures:

2 × 2 repeated-measures ANOVA was used to detect the main effects of group (ACLr, control) and fatigue state (prefatigue, postfatigue) on quadriceps:hamstring cocontraction index (Q:H CCI).

Results:

All subjects demonstrated higher Q:H CCI at prefatigue compared with postfatigue (F 1,23 = 66.949, P ≤ .001). Q:H CCI did not differ between groups (F 1,23 = 0.599, P = .447).

Conclusions:

The results indicate that regardless of fatigue state, ACLr individuals are capable of restoring muscle-activation patterns similar to those in healthy subjects. As a result, excessive muscle cocontraction, which has been hypothesized as a potential mechanism of posttraumatic OA, may not contribute to joint degeneration after ACLr.

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Anna Lina Rahlf, Klaus-Michael Braumann and Astrid Zech

Osteoarthritis is one of the most frequent musculoskeletal disorders in older adults. 1 , 2 The current global prevalence of knee osteoarthritis (OA) is 3.8%, and women are affected more often (4.8%) than men. 3 In the past, OA was generally known as degenerative cartilage decrease. Today, OA is

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Aaron Derouin and Jim R. Potvin

Injuries to the knee account for up to 60% of all sports injuries. 1 Almost half of all reported knee injuries involve disruption to the anterior cruciate ligament (ACL). 1 , 2 Functional knee braces are designed to provide support to unstable knees by reducing anterior tibial translation and

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Abbey C. Thomas, Brian G. Pietrosimone and Carter J. Bayer

Context: Transcranial magnetic stimulation (TMS) may provide important information regarding the corticospinal mechanisms that may contribute to the neuromuscular activation impairments. Paired-pulse TMS testing is a reliable method for measuring intracortical facilitation and inhibition; however, little evidence exists regarding agreement of these measures in the quadriceps. Objective: To determine the between-sessions and interrater agreement of intracortical excitability (short- and long-interval intracortical inhibition [SICI, LICI] and intracortical facilitation [ICF]) in the dominant-limb quadriceps. Design: Reliability study. Setting: Research laboratory. Participants: 13 healthy volunteers (n = 6 women; age 24.7 ± 2.1 y; height 1.7 ± 0.1 m; mass 77.1 ± 17.4 kg). Intervention: Participants completed 2 TMS sessions separated by 1 wk. Main Outcome Measures: Two investigators measured quadriceps SICI, LICI, and ICF at rest and actively (5% of maximal voluntary isometric contraction). All participants were seated in a dynamometer with the knee flexed to 90°. Intracortical-excitability paradigm and investigator order were randomized. Bland-Altman analyses were used to establish agreement. Results: Agreement was stronger between sessions within a single investigator than between investigators and for active than resting measures. Agreement was strongest for resting SICI and active ICF and LICI between sessions for each investigator. Conclusions: Quadriceps intracortical excitability may be measured longitudinally by a single investigator, though active muscle contraction should be elicited during testing.

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Jay R. Ebert and Peter K. Edwards

Autologous chondrocyte implantation (ACI) has demonstrated good clinical success in the repair of articular cartilage defects in the knee. Postoperative rehabilitation after ACI is considered critical in returning the patient to an optimal level of function by attempting to create the appropriate mechanical environment for cartilage regrowth, and it involves a progressive program that emphasizes full motion, progressive partial weight bearing (PWB), and controlled exercises. While evidence-based research is clearly lacking in all components of ACI rehabilitation, one important element in this treatment algorithm that has been subjected to some early scientific study is the gradual progression of the patient back to full weight-bearing (WB) gait after surgery. With the continual advancement of ACI surgical techniques, along with clinical experience and improved knowledge of histology and of the maturation process of chondrocytes, proposed postoperative WB protocols have evolved to better reflect the nature of the specific ACI surgery. The purpose of this article is to present the varied PWB programs that have been practiced alongside the evolving ACI surgical technique, the experimental basis for such protocols, the issues pertinent to the accurate prescription of WB, and future directions for developing such methods to best return patients to an optimal level of function after ACI.

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Brian G. Pietrosimone, Adam S. Lepley, Hayley M. Ericksen, Phillip A. Gribble and Jason Levine

Background:

Disability is common in a proportion of patients after anterior cruciate ligament reconstruction (ACL-R). Neuromuscular quadriceps deficits are a hallmark impairment after ACL-R, yet the link between muscle function and disability is not understood.

Purposes:

To evaluate the ability of quadriceps strength and cortical excitability to predict self-reported disability in patients with ACL-R.

Methods:

Fifteen participants with a history of ACL-R (11 female, 4 male; 172 ± 9.8 cm, 70.4 ± 17.5 kg, 54.4 ± 40.9 mo postsurgery) were included in this study. Corticospinal excitability was assessed using active motor thresholds (AMT), while strength was assessed with maximal voluntary isometric contractions (MVIC). Both voluntary strength and corticospinal excitability were used to predict disability measured with the International Knee Documentation Committee Index (IKDC).

Results:

The overall multiple-regression model significantly predicted 66% of the variance in self-reported disability as measured by the IKDC index (R 2 = .66, P = .01). Initial imputation of MVIC into the model accounted for 61% (R 2 = .61, P = .01) of the variance in IKDC. The subsequent addition of AMT into the model accounted for an insignificant increase of 5% (Δ R 2 = .05, P = .19) in the prediction capability of the model.

Conclusions:

Quadriceps voluntary strength and cortical excitability predicted two-thirds of the variance in disability of patients with ACL-R, with strength accounting for virtually all of the predictive capability of the model.

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Jennifer E. Earl, Jay Hertel and Craig R. Denegar

Context:

Dynamic malalignment (DM), abnormal muscle activation, and static malalignments all might lead to patellofemoral pain (PFP) but have not been examined using a multifactorial approach.

Objective:

To determine which measures of static malalignment, DM, and muscle-onset times best predict PFP.

Design and Setting:

Between-subjects, laboratory.

Subjects:

2 groups (PFP and uninjured) of 16 subjects each.

Interventions:

EMG and 3-D kinematic data were recorded during a step-down. Five static-alignment assessments were performed.

Measurements:

Three discriminant analyses using injury as the grouping variable and static measures, joint angles, and EMG onsets as the predictor variables. A final combined discriminant analysis using the most predictive variables from each set.

Results:

The static-alignment discriminant function was most predictive (81.3% correct), followed by the kinematic (69%) and the EMG (67%) functions. The final discriminant function included iliotibial-band flexibility, navicular drop, pronation, knee flexion, hip adduction, gluteus medius, and vastus medialis obliquus onset time and correctly classified 92.3% of PFP subjects.

Conclusions:

PFP can most accurately be predicted when multiple measures of lower extremity function are considered together.

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Christopher Carcia, Jim Eggen and Sandra Shultz

Context:

The influence of hip-muscle function on knee-joint kinematics during landing has been inadequately investigated.

Objective:

To determine the effect of bilateral hip-abductor fatigue on frontal-plane tibiofemoral landing characteristics and vertical ground-reaction force (vGRF) during the landing phase of a drop jump.

Design:

Experimental, pretest–posttest.

Setting:

Research laboratory.

Participants:

20 recreationally active college-age students.

Intervention:

Isometric bilateral hip-abductor-fatigue protocol.

Main Outcome Measures:

Frontal-plane tibiofemoral landing angle, excursion, and vGRF during landing from a drop jump under prefatigue, postfatigue, and recovery conditions.

Results:

After the fatigue protocol, participants landed in a greater valgus orientation than in the prefatigued state. No differences in frontal-plane excursion or vGRF were noted.

Conclusions:

Isolated bilateral hip-abductor fatigue alters frontal-plane lower extremity orientation during a double-leg landing. Because an increase in valgus orientation has been observed at or near the time of noncontact anterior cruciate ligament injuries, we recommend improving hip-abductor muscle performance to lessen the risk of such injuries.

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Gulcan Harput, H. Erkan Kilinc, Hamza Ozer, Gul Baltaci and Carl G. Mattacola

Context:

There is lack of information related to quadriceps and hamstring strength recovery during the early period of rehabilitation after anterior cruciate ligament reconstruction (ACLR) using hamstring-tendon graft (HTG).

Objective:

To investigate quadriceps and hamstring isometric strength at 4-, 8-, and 12-wk time points after ACLR and to document the strength changes of these muscles over time.

Design:

Longitudinal study.

Participants:

24 patients (age 28.1 ± 8.1 y) who underwent unilateral single-bundle anatomic ACLR with 4-strand semitendinosus and gracilis tendon graft.

Main Outcome Measures:

The isometric strength of quadriceps and hamstring muscles was measured on an isokinetic dynamometer at a 60° knee-flexion angle 4, 8, and 12 wk after surgery.

Results:

Quadriceps and hamstring strength significantly increased over time for both the involved limb (quadriceps F 2,46 = 58.3, P < .001; hamstring F 2,46 = 35.7, P < .001) and uninvolved limb (quadriceps F 2,46 = 17.9, P < .001; hamstring F 2,46 = 56.9, P = .001). Quadriceps and hamstring indexes significantly changed from 4 wk (QI 57.9, HI 54.4) to 8 wk (QI 78.8, HI 69.9) and from 8 wk to 12 wk (QI 82, HI 75.7) (P < .001); however, there was no difference between indexes at the 12-wk time point (P = .17).

Conclusions:

The results of this study serve as a reference for clinicians while directing a rehabilitation protocol for HTG ACLR patients to better appreciate expected strength changes of the muscles in the early phase of recovery.