When the Physician Becomes the Patient: Considerations for Work, Life, and Leadership.

Most orthopaedic surgeons are unprepared for serious medical illnesses. In such cases, the unique work-related and personal considerations for orthopaedic surgeons affect their career, their practice partners, and their patients. Planning together as an orthopaedic business organization for such issues can provide a framework to better navigate these difficult situations. Understanding the considerations and stressors from the individual's perspective can help provide the appropriate level of support while maintaining privacy. Throughout these considerations, open communication regarding expectations and concerns and expressions of empathy are the cornerstones of dealing with physician illness. Being a physician-patient adds complexity to an already difficult and stressful profession. Further dialogue regarding the physician-patient experience can help increase awareness of this issue and allow organizations to create a structure to best manage this almost inevitable occurrence.

Hip external rotation strength predicts hop performance after anterior cruciate ligament reconstruction.

PURPOSE: Quadriceps strength and single-leg hop performance are commonly evaluated prior to return to sport after anterior cruciate ligament reconstruction (ACLR). However, few studies have documented potential hip strength deficits after ACLR, or ascertained the relative contribution of quadriceps and hip strength to hop performance. METHODS: Patients cleared for return to sports drills after ACLR were compared to a control group. Participants' peak isometric knee extension, hip abduction, hip extension, and hip external rotation (HER) strength were measured. Participants also performed single-leg hops, timed hops, triple hops, and crossover hops. Between-limb comparisons for the ACLR to control limb and the non-operative limb were made using independent two-sample and paired sample t tests. Pearson's correlations and stepwise multiple linear regression were used to determine the relationships and predictive ability of limb strength, graft type, sex, and limb dominance to hop performance. RESULTS: Sixty-five subjects, 20 ACLR [11F, age 22.8 (15-45) years, 8.3 ± 2 months post-op, mass 70.47 ± 12.95 kg, height 1.71 ± 0.08 m, Tegner 5.5 (3-9)] and 45 controls [22F, age 25.8 (15-45) years, mass 74.0 ± 15.2 kg, height 1.74 ± 0.1 m, Tegner 6 (3-7)], were tested. Knee extension (4.4 ± 1.5 vs 5.4 ± 1.8 N/kg, p = 0.02), HER (1.4 ± 0.4 vs 1.7 ± 0.5 N/kg, p = 0.04), single-leg hop (146 ± 37 vs 182 ± 38% limb length, p < 0.01), triple hop (417 ± 106 vs 519 ± 102% limb length, p < 0.01), timed hop (3.3 ± 2.0 vs 2.3 ± 0.6 s, p < 0.01), and crossover hop (364 ± 107 vs 446 ± 123% limb length, p = 0.01) were significantly impaired in the operative versus control subject limbs. Similar deficits existed between the operative and non-operative limbs. Knee extension and HER strength were significantly correlated with each of the hop tests, but only HER significantly predicted hop performance. CONCLUSIONS: After ACLR, patients have persistent HER strength, knee extension strength, and hop test deficits in the operative limb compared to the control and non-operative limbs, even after starting sport-specific drills. Importantly, HER strength independently predicted hop performance. Based on these findings, to resolve between-limb deficits in strength and hop performance clinicians should include HER strengthening exercises in post-operative rehabilitation. LEVEL OF EVIDENCE: Prognostic Study, Level II.

The Relationship Between Hip Strength and the Y Balance Test.

CONTEXT: The Y Balance Test was developed as a test of dynamic postural control and has been shown to be predictive of lower-extremity injury. However, the relationship between hip strength and performance on the Y Balance Test has not been fully elucidated. OBJECTIVE: The goal of this study was to identify the relationship between components of isometric hip strength and the Y Balance Test, to provide clinicians better guidance as to specific areas of muscle performance to address in the event of poor performance on the Y Balance Test. DESIGN: Laboratory study. SETTING: Biomechanics laboratory. PARTICIPANTS: A total of 73 healthy participants (40 males and 33 females) volunteered for this study. INTERVENTION: None. MAIN OUTCOME MEASURES: Participants completed the Y Balance Test on the right leg. The authors then measured peak isometric torque in hip external rotation, abduction, and extension. Correlations were calculated between torque measurements, normalized for mass and Y Balance Test performance. Significant relationships were used in linear regression models to determine which variables were predictive of the Y Balance Test performance. RESULTS: The authors found significant positive correlations between Y Balance Test performance and hip abduction strength. They also found correlations between the Y Balance Test and hip extension and external rotation strengths. Linear regression analysis showed hip abduction to be the only significant predictor of Y Balance performance. CONCLUSIONS: The authors found the strongest association between the Y Balance Test and hip abduction strength. They also showed smaller but significant associations with hip extension and external rotation strength. When entered into a linear regression analysis, hip abduction strength was the only significant predictor of Y Balance performance. Using this information, practitioners should look to hip abduction strength when patients exhibit deficits in the Y Balance Test.

Incidence of Osteoarthritis Diagnosis Within 5 Years of Surgery Was Greater Following Partial Meniscectomy Than Meniscus Repair and/or Anterior Cruciate Ligament Reconstruction.

Purpose: To compare knee osteoarthritis (OA) incidence within 5 years of surgery between 5 common sports medicine procedures: isolated anterior cruciate ligament (ACL) reconstruction, isolated meniscus repair (MR), isolated arthroscopic partial meniscectomy (APM), ACL reconstruction with MR (ACL + MR), and ACL reconstruction with APM (ACL + APM). Methods: The PearlDiver Mariner M157Ortho database was searched. Five cohorts were identified using Current Procedural Terminology (CPT) codes and included those 16 to 60 years old who underwent isolated ACL reconstruction, isolated MR, ACL + MR, isolated APM, or ACL + APM repair. Groups were matched by age, sex, and presence of diagnosis codes for obesity. The incidence of knee OA diagnosis within 5 years of the index procedure was determined for each group, and odds ratios (ORs) were calculated and compared against isolated ACL reconstruction. Results: Each group consisted of 7,672 patients (3,450 females, 4,222 males). A significantly greater proportion of the APM group was diagnosed with knee OA within 5 years of surgery compared to isolated ACL reconstruction (APM = 1,032/7,672 [13.5%] vs ACL = 745/7,672 [9.7%]; P ≤ .001; OR, 1.45; 95% confidence interval [CI], 1.31-1.60). Similarly, a greater proportion of the MR group was diagnosed with OA compared to isolated ACL reconstruction (MR = 826/7,672 [10.7%]; P = .030; OR, 1.12; 95% CI, 1.01-1.25). No differences in OA incidence were noted between the ACL + APM group when compared to isolated ACL reconstruction (P = .81). Patients undergoing ACL + MR demonstrated the lowest OA incidence with reduced odds when compared to isolated ACL reconstruction (ACL + MR = 575/7,672 [7.5%]; P < .001; OR, 0.75; 95% CI, 0.67-0.84). Conclusions: In this analysis using CPT codes, APM was associated with the highest knee OA incidence, and ACL + MR was associated with the lowest OA incidence within 5 years of surgery. Level of Evidence: Level III, retrospective cohort study.

Quadriceps Strength and Kinesiophobia Predict Long-Term Function After ACL Reconstruction: A Cross-Sectional Pilot Study.

BACKGROUND: Many patients live with long-term deficits in knee function after an anterior cruciate ligament reconstruction (ACLR). However, research is inconclusive as to which physical performance measure is most strongly related to long-term patient-reported outcomes after ACLR. HYPOTHESIS: Quadriceps strength would be most strongly associated with patient-reported long-term outcomes after ACLR. STUDY DESIGN: Cross-sectional study. LEVEL OF EVIDENCE: Level 3. METHODS: A total of 40 patients (29 female) consented and participated an average of 10.9 years post-ACLR (range, 5-20 years). Patients completed the Lower Extremity Functional Scale (LEFS), the International Knee Documentation Committee (IKDC) Scale, Knee injury and Osteoarthritis Outcome Score Quality of Life (KOOS QoL) and Sport (KOOS Sport) subscales, and the Tampa Scale of Kinesiophobia (TSK-17). Each patient subsequently performed maximal isometric quadriceps contraction, a 60-second single-leg step-down test, and the single-leg single hop and triple hop for distance tests. Multivariate linear and logistic regression models determined how performance testing was associated with each patient-reported outcome when controlling for time since surgery, age, and TSK-17. RESULTS: When controlling for time since surgery, age at the time of consent, and TSK-17 score, maximal isometric quadriceps strength normalized to body weight was the sole physical performance measure associated with IKDC (P < 0.001), KOOS Sport (P = 0.006), KOOS QoL (P = 0.001), and LEFS scores (P < 0.001). Single-leg step-down, single hop, and triple hop did not enter any of the linear regression models (P > 0.20). Additionally, TSK-17 was associated with all patient-reported outcomes (P ≤ 0.01) while time since surgery was not associated with any outcomes (P > 0.05). CONCLUSION: Isometric quadriceps strength and kinesiophobia are significantly associated with long-term patient-reported outcomes after ACLR. CLINICAL RELEVANCE: These results suggest that training to improve quadriceps strength and addressing kinesiophobia in the late stages of recovery from ACLR may improve long-term self-reported function.

Secondary Injuries After Pediatric Anterior Cruciate Ligament Reconstruction: A Systematic Review With Quantitative Analysis.

BACKGROUND: In the skeletally mature anterior cruciate ligament (ACL) reconstruction population, patients aged <25 years are at significantly increased risk of graft failure and injury to the contralateral ACL. Skeletal immaturity often affects graft selection and reconstruction technique. PURPOSE: To examine the incidence of ipsilateral graft failure and contralateral ACL injury in the skeletally immature patient population. STUDY DESIGN: Systematic review and meta-analysis. METHODS: Using the PRISMA (Preferred Reporting Items for Systematic Meta-Analyses) guidelines, we reviewed all literature that involved ACL reconstruction performed on skeletally immature patients between May 1976 and May 2019. Patient demographics, surgical technique, and the prevalence of ipsilateral graft failure or subsequent contralateral ACL injury were recorded. Ipsilateral, contralateral, and secondary ACL injuries were then compared between sexes via chi-square tests. RESULTS: A total of 24 articles (1254 children; 1258 knees) met inclusion criteria for analysis. Ipsilateral graft failures occurred in 105 of 1258 patients (8.3%), and there were no statistically significant sex differences in the prevalence of graft failures (female, 9.7%; male patients, 7.1%; P = .14). The prevalence of contralateral ACL injury was significantly greater in female (29/129; 22.5%) than male (18/206; 8.7%; P = .0004) patients in the 9 studies that reported contralateral injury. Skeletally immature female patients were at significantly increased risk of contralateral ACL injury (odds ratio = 3.0; P = .0006) when compared with their male counterparts. CONCLUSION: In the literature to date, 1 in 3 female skeletally immature patients experienced an ipsilateral graft failure or contralateral ACL injury. Regardless of sex, the 24% prevalence of secondary injury after pediatric ACL reconstruction is almost identical to previously published secondary injury rates in skeletally mature patients <25 years old. As such, skeletal maturity alone does not seem to be a determinant of secondary injury; however, there is a clear need to improve postoperative rehabilitation, activity progression, and return-to-play testing to allow a safe return to sports that protects the long-term health of the reconstructed and contralateral limbs, especially for female patients.

Decreased quadriceps force steadiness following anterior cruciate ligament reconstruction is associated with altered running kinematics.

BACKGROUND: Anterior cruciate ligament reconstruction is associated with quadriceps dysfunction and altered knee mechanics, but the relationship between these outcomes is not clear. Inclusion of metrics such as the stability of torque output could provide additional insights into the relationship between quadriceps dysfunction and knee mechanics. The purposes of this study were to: (1) measure the difference in quadriceps force steadiness between anterior cruciate ligament reconstructed and contralateral limbs; and (2) assess the relationship of quadriceps force steadiness and peak torque with knee flexion excursion during running. METHODS: Twenty-eight participants (14 female, age 20 (5) years) underwent quadriceps strength testing and gait analysis. Force steadiness was measured with the standard deviation and coefficient of variation of the participants' detrended torque. Knee flexion excursion was calculated during the stance phase of running trials. Differences between limbs for force steadiness and peak torque were assessed with paired sample t-tests, and a Pearson's product-moment correlation coefficient determined the relationship between pairs of variables. FINDINGS: Anterior cruciate ligament reconstructed limbs presented with a significant deficit in relative force steadiness compared to the contralateral limb (4.03 (1.04) % and 3.58 (1.41) % (P < .05), respectively). In addition, the relationship of quadriceps strength and force steadiness with knee flexion excursion was altered in anterior cruciate ligament reconstructed limbs due to the inability of the quadriceps to sustain a controlled force output. INTERPRETATION: These results suggest that considering both the magnitude and quality of force production can provide important insight into comprehensive quadriceps function.

Anterior Cruciate Ligament Tear Promotes Skeletal Muscle Myostatin Expression, Fibrogenic Cell Expansion, and a Decline in Muscle Quality.

BACKGROUND: Anterior cruciate ligament (ACL) tears result in significant quadriceps muscle atrophy that is resistant to recovery despite extensive rehabilitation. Recent work suggests an elevated fibrotic burden in the quadriceps muscle after the injury, which may limit recovery. Elucidating the mechanisms and cell types involved in the progression of fibrosis is critical for developing new treatment strategies. PURPOSE: To identify factors contributing to the elevated fibrotic burden found after the injury. STUDY DESIGN: Descriptive laboratory study. METHODS: After an ACL injury, muscle biopsy specimens were obtained from the injured and noninjured vastus lateralis of young adults (n = 14, mean ± SD: 23 ± 4 years). The expression of myostatin, transforming growth factor ß, and other regulatory factors was measured, and immunohistochemical analyses were performed to assess turnover of extracellular matrix components. RESULTS: Injured limb skeletal muscle demonstrated elevated myostatin gene ( P < .005) and protein ( P < .0005) expression, which correlated ( R2 = 0.38, P < .05) with fibroblast cell abundance. Immunohistochemical analysis showed that human fibroblasts express the activin type IIB receptor and that isolated primary human muscle-derived fibroblasts increased proliferation after myostatin treatment in vitro ( P < .05). Collagen 1 and fibronectin, primary components of the muscle extracellular matrix, were significantly higher in the injured limb ( P < .05). The abundance of procollagen 1-expressing cells as well as a novel index of collagen remodeling was also elevated in the injured limb ( P < .05). CONCLUSION: These findings support a role for myostatin in promoting fibrogenic alterations within skeletal muscle after an ACL injury. CLINICAL RELEVANCE: The current work shows that the cause of muscle quality decline after ACL injury likely involves elevated myostatin expression, and future studies should explore therapeutic inhibition of myostatin to facilitate improvements in muscle recovery and return to sport.

Delayed Presentation of Compartment Syndrome of the Thigh in a Previously Undiagnosed Factor VII-Deficient High School Football Athlete: A Case Report.

CASE: We describe a case of delayed presentation of compartment syndrome in the anterior aspect of the thigh in a high school athlete. The patient had sustained a blow to the thigh 8 days prior to presentation, and had continued to practice football in the setting of undiagnosed coagulopathy. He presented with severe thigh pain and the inability to contract the thigh muscles. CONCLUSION: A high index of suspicion for compartment syndrome is indicated for patients with disproportionate pain, especially in the setting of relatively minor trauma. Underlying coagulopathy should be investigated in patients with compartment syndrome because there is a high incidence of bleeding disorders in this population.

Sex-based Differences in Common Sports Injuries.

The patient's sex plays an important role in mediating the risk for, and experience of, disease. Injuries of the musculoskeletal system are no exception to this phenomenon. Increasing evidence shows that the incidence, clinical presentation, and treatment outcomes for male and female patients with common sports injuries may vary widely. Stress fracture, which is associated with the female athlete triad, is a sports injury with known sex-based differences. Other common sports-related injuries may also have distinct sex-based differences. Understanding these differences is important to optimize each patient's musculoskeletal care.

Neuromuscular compensatory strategies at the trunk and lower limb are not resolved following an ACL reconstruction.

BACKGROUND: Following anterior cruciate ligament reconstruction (ACLR), patients present with greater trunk ipsilateral lean, which may affect knee kinetics and increase re-injury risk. However, there has been little research into neuromuscular factors controlling the trunk and their relation to the knee between healthy and ACLR subjects. This is critical to establish in order to develop more directed and effective interventions. HYPOTHESIS: As compared to healthy control subjects, ACLR subjects will demonstrate increased erector spinae and rectus abdominis co-contraction, greater rectus abdominis force and greater hamstring force that is correlated to increased forward trunk lean. STUDY DESIGN: Cross-sectional study, Level of Evidence: 3. METHODS: Eleven healthy and eleven ACLR subjects were matched for age, mass and height. Subjects were asked to run at a self-selected speed while instrumented gait analysis was performed. An anthropometrically scaled OpenSim model was created for each subject. Trunk and hamstring muscle forces from Static Optimization were analyzed at impact peak. Additionally, directed co-contraction ratios were calculated for the erector spinae and erector spinae/rectus abdominis combinations. RESULTS: ACLR subjects showed more balanced erector spinae co-contraction [p<0.01], and greater hamstring force [biceps femoris long head (p=0.02), semimembranosus (0.01), semitendinosus (0.01)]. There was no statistical difference for any other muscle group. CONCLUSION: Despite release to return to sport, ACLR subjects are continuing to increase the stiffness of their trunk as well increase their hamstring force to potentially reduce anterior tibial translation. CLINICAL RELEVANCE: Clinicians may anticipate ACLR subjects using their erector spinae and hamstrings to maintain a sense of stability in their trunk and at their knee.

ACL injury reduces satellite cell abundance and promotes fibrogenic cell expansion within skeletal muscle.

Anterior cruciate ligament (ACL) injuries are associated with significant loss of strength in knee extensor muscles that persists despite physical therapy. The underlying mechanisms responsible for this protracted muscle weakness are poorly understood; however, we recently showed significant myofiber atrophy and altered muscle phenotype following ACL injury. We sought to further explore perturbations in skeletal muscle morphology and progenitor cell activity following an ACL injury. Muscle biopsies were obtained from the injured and non-injured vastus lateralis of young adults (n = 10) following ACL injury, and histochemical/immunohistochemical analyses were undertaken to determine collagen content, abundance of connective tissue fibroblasts, fibrogenic/adipogenic progenitor (FAP) cells, satellite cells, in addition to indices of muscle fiber denervation and myonuclear apoptosis. The injured limb showed elevated collagen content (p < 0.05), in addition to a greater abundance of fibroblasts and FAPs (p < 0.05) in the injured limb. Fibroblast content was correlated with increased accumulation of extracellular matrix in the injured limb as well. A higher frequency of interstitial nuclei were positive for phospho-SMAD3 in the injured limb (p < 0.05), providing some evidence for activation of a fibrogenic program through transforming growth factor ß following an ACL injury. The injured limb also displayed reduced satellite cell abundance, increased fiber denervation and DNA damage associated with apoptosis (p < 0.05), indicating alterations within the muscle itself after the ligament injury. Injury of the ACL induces a myriad of negative outcomes within knee extensor muscles, which likely compromise the restorative capacity and plasticity of skeletal muscle, impeding rehabilitative efforts. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1876-1885, 2017.

Anatomic Femoral and Tibial Tunnel Placement During Anterior Cruciate Ligament Reconstruction: Anteromedial Portal All-Inside and Outside-In Techniques.

Tunnel malposition is one of the most common technical reasons for anterior cruciate ligament reconstruction failure. Small changes in tunnel placement can result in significant differences in outcome. More anatomic placement of the tunnels can lead to greater knee stability and a more accurate reproduction of native knee kinematics. This Technical Note describes 2 tibial tunnel-independent methods to obtain anatomic femoral tunnel placement. The all-inside anteromedial portal technique requires only minimal surgical incisions but allows precise femoral tunnel placement. However, hyperflexion of the knee is required, adequate surgical assistance is necessary, and this technique may be susceptible to graft-tunnel mismatch. The outside-in technique may be more beneficial in obese patients, skeletally immature patients, or revision cases. On the downside, it does require an additional 2-cm surgical incision. This article also provides surgical pearls to fine-tune tibial tunnel placement.

Core strength and lower extremity alignment during single leg squats.

INTRODUCTION/PURPOSE: Muscles of the trunk, hip, and knee influence the orientation of the lower extremity during weight bearing activities. The purpose of this study was threefold: first, to compare the orientation of the lower extremity during a single leg (SL) squat among male and female athletes; second, to compare the strength of muscle groups in the trunk, hips, and knees between these individuals; and third, to evaluate the association between trunk, hip, and knee strength and the orientation of the knee joint during this activity. METHODS: Twenty-four male and 22 female athletes participated in this study. Peak isometric torque was determined for the following muscle actions: trunk flexion, extension, and lateral flexion, hip abduction and external rotation, and knee flexion and extension. The frontal plane projection angle (FPPA) of the knee during a 45 degrees SL squat was determined using photo editing software. RESULTS: Males and females moved in opposite directions during the SL squat test (F(1,42) = 5.05, P = 0.03). Females typically moved toward more extreme FPPA during SL squats (P = 0.056), while males tended to move toward more neutral alignment (P = 0.066). Females also generated less torque in all muscle groups, with the exception of trunk extension. The projection angle of the knee during the SL squat test was most closely associated with hip external rotation strength. CONCLUSION: Using instruments suitable for a clinical setting, females were found to have greater FPPA and generally decreased trunk, hip, and knee isometric torque. Hip external rotation strength was most closely associated with the frontal plane projection angle.

Understanding and preventing noncontact anterior cruciate ligament injuries: a review of the Hunt Valley II meeting, January 2005.

The incidence of noncontact anterior cruciate ligament injuries in young to middle-aged athletes remains high. Despite early diagnosis and appropriate operative and nonoperative treatments, posttraumatic degenerative arthritis may develop. In a meeting in Atlanta, Georgia (January 2005), sponsored by the American Orthopaedic Society for Sports Medicine, a group of physicians, physical therapists, athletic trainers, biomechanists, epidemiologists, and other scientists interested in this area of research met to review current knowledge on risk factors associated with noncontact anterior cruciate ligament injuries, anterior cruciate ligament injury biomechanics, and existing anterior cruciate ligament prevention programs. This article reports on the presentations, discussions, and recommendations of this group.

Clinical Predictors of Knee Mechanics at Return to Sport after ACL Reconstruction.

PURPOSE: Despite significant rehabilitation, many athletes experience protracted weakness and faulty mechanics after anterior cruciate ligament reconstruction (ACLR). Clinical tests performed early in rehabilitation, which predict knee mechanics at return-to-sport, are virtually unknown and critically needed to guide clinical decision making. The purpose of this study is to determine if quadriceps strength, Y balance anterior (YB-A) reach distance, and single-leg step-down test performance (SLSD) conducted 3 months post-ACLR are predictive of knee flexion excursion (KFLEX) and knee extensor moment (KEM) during running 6 months post-ACLR. METHODS: Thirty (16 females) subjects were collected 3 and 6 months post-ACLR. Age, 21.3 ± 7.6 yr; mass, 69.85 ± 11.4 kg; height, 1.73 ± 0.09 m. At 3 months post-ACLR, subjects performed isometric quadriceps strength testing, YB-A, and SLSD assessments. At 6 months post-ACLR, subjects underwent three-dimensional motion analysis while running on an instrumented treadmill. Pearson correlation coefficients and stepwise multiple regression were used to assess the relationships of 3-month and 6-month variables. RESULTS: Quadriceps strength (r = 0.493, P < 0.01), YB-A (r = 0.394, P = 0.03), and SLSD (r = 0.648, P < 0.01) were significantly correlated to KFLEX. Quadriceps strength (0.505, P < 0.01) and SLSD (.541, P < 0.01) were significantly correlated with KEM, whereas YB-A (.276, P = 0.06) was not. SLSD and quadriceps strength were predictive of KEM (adj R², 0.36; P = 0.001) whereas only SLSD was predictive of KFLEX (adj R², 0.40; P < 0.001). CONCLUSIONS: After ACLR, better performance in SLSD and quadriceps strength 3 months postsurgery is predictive of improved sagittal plane knee mechanics during running 6 months postsurgery.

Cellular and Morphological Alterations in the Vastus Lateralis Muscle as the Result of ACL Injury and Reconstruction.

BACKGROUND: Individuals who have had an anterior cruciate ligament (ACL) tear and reconstruction continue to experience substantial knee extensor strength loss despite months of physical therapy. Identification of the alterations in muscle morphology and cellular composition are needed to understand potential mechanisms of muscle strength loss, initially as the result of the injury and subsequently from surgery and rehabilitation. METHODS: We performed diffusion tensor imaging-magnetic resonance imaging and analyzed muscle biopsies from the vastus lateralis of both the affected and unaffected limbs before surgery and again from the reconstructed limb following the completion of rehabilitation. Immunohistochemistry was done to determine fiber type and size, Pax-7-positive (satellite) cells, and extracellular matrix (via wheat germ agglutinin straining). Using the diffusion tensor imaging data, the fiber tract length, pennation angle, and muscle volume were determined, yielding the physiological cross-sectional area (PCSA). Paired t tests were used to compare the effects of the injury between injured and uninjured limbs and the effects of surgery and rehabilitation within the injured limb. RESULTS: We found significant reductions before surgery in type-IIA muscle cross-sectional area (CSA; p = 0.03), extracellular matrix (p < 0.01), satellite cells per fiber (p < 0.01), pennation angle (p = 0.03), muscle volume (p = 0.02), and PCSA (p = 0.03) in the injured limb compared with the uninjured limb. Following surgery, these alterations in the injured limb persisted and the frequency of the IIA fiber type decreased significantly (p < 0.01) and that of the IIA/X hybrid fiber type increased significantly (p < 0.01). CONCLUSIONS: Significant and prolonged differences in muscle quality and morphology occurred after ACL injury and persisted despite reconstruction and extensive physical therapy. CLINICAL RELEVANCE: These results suggest the need to develop more effective early interventions following an ACL tear to prevent deleterious alterations within the quadriceps.

Relationship of Hip and Trunk Muscle Function with Single Leg Step-Down Performance: Implications for Return to Play Screening and Rehabilitation.

OBJECTIVES: Evaluate the relationship of hip and trunk muscle function with the Single Leg Step-Down test (SLSD). STUDY DESIGN: Laboratory study. SETTING: Biomechanics Laboratory. PARTICIPANTS: 71 healthy participants with no history of anterior cruciate ligament (ACL) or lower extremity injury in the last 3 months completed this study (38 males, 33 females; mean 25.49 ± 0.62 years). MAIN OUTCOMES: Hip abduction (HABD), external rotation (HER), and extension (HEXT) peak isometric force were measured. Trunk endurance was measured with plank (PL) and side plank (SPL) tests. SLSD repetitions in 60-s and dynamic knee valgus (VAL) were recorded. RESULTS: PL, SPL, HABD, HER, and HEXT were positively correlated with SLSD repetitions. PL (r = 0.598, p < 0.001) was most correlated with SLSD repetitions, and regression demonstrated that PL (p = 0.001, R2 = 0.469) was a predictor of SLSD repetitions. VAL trended toward negative correlation with PL and SPL. Sex-specific differences were present, with PL, SPL, HABD, and HER showing stronger relationships with SLSD in females. CONCLUSION: Hip and trunk muscle function were positively correlated with SLSD performance, and these relationships were strongest in females. PL predicted performance on the SLSD. Further research is needed to investigate the utility of SLSD as a screening or return-to-play test for lower extremity conditions such as ACL injury and patellofemoral pain.

Core stability and its relationship to lower extremity function and injury.

Core stability may provide several benefits to the musculoskeletal system, from maintaining low back health to preventing knee ligament injury. As a result, the acquisition and maintenance of core stability is of great interest to physical therapists, athletic trainers, and musculoskeletal researchers. Core stability is the ability of the lumbopelvic hip complex to prevent buckling and to return to equilibrium after perturbation. Although static elements (bone and soft tissue) contribute to some degree, core stability is predominantly maintained by the dynamic function of muscular elements. There is a clear relationship between trunk muscle activity and lower extremity movement. Current evidence suggests that decreased core stability may predispose to injury and that appropriate training may reduce injury. Core stability can be tested using isometric, isokinetic, and isoinertial methods. Appropriate intervention may result in decreased rates of back and lower extremity injury.