Hamstring weakness as an indicator of poor knee function in ACL-deficient patients

Specificity of isokinetic assessment in noncontact knee injury prevention screening: A novel assessment procedure with relationships between variables in amateur adult agility-sport athletes

OBJECTIVES

To present a new knee isokinetic assessment procedure linked to noncontact knee injury mechanisms and examine correlations between variables relevant to noncontact knee injury prevention screening (peak torque [PT, Nm], time-to-peak torque [TTPT, ms], angle-of-peak torque [APT, °], mean PT [MPT, Nm]).

DESIGN

Cross-sectional.

SETTING

Sports medicine laboratory.

PARTICIPANTS

Thirty-four agility-sport athletes (male/female n = 18/16, age 24.1 ± 3.5yr, height 171.8 ± 9.6 cm, mass 70.6 ± 12 kg).

MAIN OUTCOME MEASURES

Pearson's/Spearman's correlation (r/r_s), coefficient of determination (r²/r_s²).

RESULTS

Most correlations were statistically non-significant or statistically-significant with only weak-to-moderate coefficients. For both knee extension and flexion, PT and MPT were significantly and strongly correlated (r = 0.99, r² = 0.98, p = 0.001). Graphical analyses revealed two datapoint clusters for knee flexion TTPT and APT. One cluster indicated some participants could generate knee flexor PT rapidly (<150 ms) at low knee flexion angles (<45°) and the other cluster indicated that other participants could not (>200 ms, >50°).

CONCLUSIONS

In this study, most isokinetic variables represented distinct knee neuromuscular characteristics. For both knee extension and flexion, only PT or MPT need be used to represent isokinetic maximal strength. Knee flexion TTPT and APT may have utility in noncontact knee injury prevention screening with amateur adult agility-sport athletes.

Internal Fixation of Lateral Trochlear Groove Osteochondritis Dissecans With Simultaneous Lateral Retinacular Lengthening in Adolescent Athletes

BACKGROUND

The goals of operative treatment for the adolescent athlete with unstable osteochondritis dissecans (OCD) lesion are rigid fixation and prevention of recurrence.

PURPOSE

To evaluate clinical and radiological outcomes of internal fixation of lateral trochlear groove OCD with simultaneous lateral retinacular lengthening.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Adolescent athletes who had undergone internal fixation and simultaneous lateral retinacular lengthening for an unstable OCD lesion of the lateral trochlear groove were retrospectively reviewed. Subjective assessments included the Lysholm score, International Knee Documentation Committee (IKDC) subjective score, Tegner activity scale, and an athletic questionnaire. Functional tests included isokinetic muscle strength, single-leg hop for distance, single-leg vertical jump, and Y-balance. Pre- and postoperative radiographs and magnetic resonance images were reviewed.

RESULTS

The mean ± SD age of the 17 patients included in this study was 15.9 ± 0.9 years; last clinical follow-up duration was 37.7 ± 8.1 months. At the last follow-up, the Lysholm score improved from 68.7 ± 15.3 to 93.4 ± 12.4 and the IKDC subjective score from 60.2 ± 14.7 to 88.7 ± 12.7 (P < .001). The mean Tegner activity scale score was 9.4 ± 0.5 before injury and 8.9 ± 1.2 at the last follow-up (P = .059). The limb symmetry indices of isokinetic muscle strength, single-leg hop for distance, single-leg vertical jump, and Y-balance improved at the last follow-up; the mean limb symmetry index was ≥85% in each functional test. Regarding the athletic questionnaire, 16 (94.1%) patients were satisfied with the surgery. At the last follow-up, 2 patients had higher ability after returning to sports, 11 had the same ability, and 3 had lower ability than the preinjury level. Postoperative magnetic resonance imaging at 12-month follow-up showed that the OCD lesion appeared healed in 7 (41.2%) patients and partially healed in 9 (52.9%).

CONCLUSION

Internal fixation of lateral trochlear groove OCD with simultaneous lateral retinacular lengthening in adolescent athletes achieved satisfactory clinical and radiological outcomes. Therefore, this combined surgical technique could be considered an effective treatment for lateral trochlear groove OCD, with a high rate of return to sport.

The effectiveness of vibration therapy for muscle peak torque and postural control in individuals with anterior cruciate ligament reconstruction: a systematic review and meta-analysis of clinical trials

Objective

This study aimed to review and summarize the existing evidence on the effectiveness of vibration therapy (VT) in comparison with conventional rehabilitation in anterior cruciate ligament (ACL)-reconstructed patients considering muscle peak torque and postural control.

Methods

We searched available online databases for relevant studies published up to February 2020. All randomized clinical trials investigating the effect of VT on quadriceps peak torque, hamstring peak torque, and postural control (closed-eye and open-eye) were included. Overall, 13 clinical trials with a total sample size of 407 participants were included for the meta-analysis. We used the pooled mean difference with random effects model for meta-analyses. We assessed the heterogeneity of the studies using the I² and Cochran’s Q test. Meta-regression analysis was used to assess the source of heterogeneity.

Results

We found that VT significantly improved hamstring peak torque [weighted mean difference (WMD) 12.67, 95% CI 4.51–20.83] and quadriceps peak torque (WMD 0.11, 95% CI −0.06 to 0.29). However, subgroup analysis showed a significant increase in mentioned muscles’ peak torque in studies employing interventions including both local muscle vibration (LMV) and vibration frequency higher than 100 Hz (WMD 20.84, 95% CI 11.75–29.93). With regard to postural control, we observed a significant improvement only in open-eye mediolateral postural control (WMD 0.26, 95% CI −1.26 to 1.77).

Conclusion

This study suggests that VT, especially LMV type with vibration frequency higher than 100 Hz, can be effective in rehabilitation of ACL-reconstructed patients. Although improvement in the peak torque of hamstring and quadriceps muscles was seen, there was no significant improvement in postural control, especially closed-eye, in comparison with conventional rehabilitation.

Level of evidence

1.

Highlights

Vibration therapy can increase hamstring peak torque in individuals with ACL reconstruction.

Local muscle vibration type in comparison with whole-body vibration is recommended for ACL-reconstructed patients.

Vibration frequency higher than 100 Hz is preferred in ACL-reconstructed rehabilitation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10195-021-00589-5.

Anatomic medial complex reconstruction in serious medial knee instability results in excellent mid-term outcomes

PURPOSE

To evaluate the mid-term outcomes of anatomic medial complex reconstruction in cases of serious medial knee instability.

METHODS

Between 2010 and 2013, 23 patients who underwent anatomic medial complex reconstruction with a minimum 5-year follow-up were included. The Lysholm score, International Knee Documentation Committee subjective knee form (IKDC SKF), and Tegner activity scale scores were evaluated. Clinical and functional tests included valgus and sagittal stress tests, isokinetic muscle strength test, single leg hop for distance test (SLDT), and single leg vertical jump test (SLVT).

RESULTS

The mean follow-up duration was 77.2 ± 10.8 months. At final follow-up, the Lysholm score improved from 49.7 ± 10.2 to 93.4 ± 12.4; the IKDC SKF score, from 46.2 ± 8.7 to 90.5 ± 13.9; and median Tegner activity, from 5 (4-7) to 7 (4-10) (P < 0.001). The mean side-to-side difference on valgus stress radiographs was significantly reduced to 1.2 ± 0.7 mm postoperatively compared to 8.5 ± 1.6 mm preoperatively (P < 0.001). The mean side-to-side differences on anterior and posterior stress radiographs were significantly improved in concomitant ACL and PCL reconstructions, respectively (P < 0.001). Preoperatively, 17 patients (73.9%) had anteromedial rotatory instability (AMRI), but none had AMRI at the last follow-up. The extensor peak torque and Limb Symmetry Index (LSI, %) improved from 128.2 ± 42.9 to 225 ± 39.4 N m/kg and from 61.4 ± 19.6 to 88.7 ± 21.7%, respectively (P < 0.001). The LSI (%) for SLDT and SLVT improved from 56.8 ± 19.5 to 87.3 ± 14.2% and from 68.1 ± 21.1 to 91.1 ± 12.8%, respectively (P < 0.001). No patient had a restricted range of movement.

CONCLUSION

Although posteromedial corner injuries that need medial complex reconstruction are extremely rare, proper anatomic medial complex reconstruction of the medial collateral and posterior oblique ligaments achieved satisfactory clinical and functional outcomes at mid-term follow-up in cases with chronic symptomatic valgus and rotatory laxity.

LEVEL OF EVIDENCE

Case series, level IV.

Return to Sports and Clinical Outcomes After Arthroscopic Anatomic Posterior Cruciate Ligament Reconstruction With Remnant Preservation

PURPOSE

To evaluate the clinical outcomes of transtibial posterior cruciate ligament reconstruction (PCLR) with remnant preservation in highly active patients and to investigate the rate of return to sports (RTS), quality of sports activities, and patient satisfaction.

METHODS

Patients with a Tegner activity scale of >5 who underwent isolated PCLR from 2013 to 2016 with minimum 2-year follow-up were retrospectively reviewed. Single-bundle PCLR was performed using fresh frozen allograft irradiated with 50 kGy. Subjective assessments included the Lysholm score, subjective International Knee Documentation Committee score, and Tegner activity scale. A questionnaire elicited information associated with RTS and satisfaction. Functional tests included isokinetic muscle strength and single-leg hop tests.

RESULTS

We evaluated 52 patients, with a mean (± standard deviation) follow-up duration of 29.5 ± 8.6 months. The subjective assessments and functional tests significantly improved postoperatively (all P < .001). Mean time to return to full sports activity was 9.7 ± 5.1 months. Thirty-eight (73.1%) and 45 (86.5%) patients could return to previous sports activities at 9 and 24 months, respectively. A sports-experience questionnaire indicated that 48% and 69.2% of the patients were participating with unlimited effort and performance, respectively, and no pain at 9 and 24 months. Multivariate analysis indicated that extensor deficit (odds ratio [OR] 4.2, 95% confidence interval [CI] 1.342 to 17.839), flexor deficit at 60°/s (OR 3.8, 95% CI 1.081 to 14.476), Limb Symmetry Index (%) for the single-leg vertical jump test (OR 2.2, 95% CI 1.212 to 9.227), and satisfaction (OR 2.8, 95% CI 1.186 to 10.281) were significantly associated with failure of not returning to preinjury sports activity levels at the 9-month follow-up.

CONCLUSIONS

Arthroscopic anatomic PCLR with remnant preservation showed high rates of RTS and high patient satisfaction, as well as satisfactory clinical results in highly active patients. This surgical technique could be an effective treatment for grade III posterior cruciate ligament injury in highly active patients.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Isokinetic knee strength and proprioception before and after anterior cruciate ligament reconstruction: A comparison between home-based and supervised rehabilitation

BACKGROUND

Rehabilitation after anterior cruciate ligament (ACL) reconstruction focuses on restoring knee deficiencies and function. However, the extent of the clinician's direct supervision that is required to recover knee function is unknown.

OBJECTIVE

To investigate differences in isokinetic knee strength improvement, endurance, and proprioception between home-based (HBR) and supervised rehabilitation (SR).

METHODS

Thirty participants were randomly allocated to each group after reconstruction. Isokinetic knee strength and proprioception were measured using the Biodex multi-joint and stability systems, respectively, before and after intervention.

RESULTS

The SR group showed a significant improvement from baseline, but not the HBR group (SR group, from 1.94 ± 1.44 to 1.02 ± 0.92, p< 0.05; HBR group, from 1.69 ± 0.88 to 1.61 ± 0.90, p> 0.05). There was a significant effect of exercise type on proprioception scores after controlling for pretest values (p< 0.05). No significant difference in isokinetic knee strength was observed between the groups.

CONCLUSIONS

HBR recovered knee strength as effectively as the SR, but SR was more effective than HBR for the recovery of proprioception and functional knee movement. This result indicates that guidance from health professionals play an important role in enhancing proprioception for patients following ACL reconstruction.

The hamstring/quadriceps ratio is an indicator of function in ACL-deficient, but not in ACL-reconstructed knees

PURPOSE

The purpose of this study was to investigate the isokinetic, eccentric and isometric hamstring/quadriceps (HQ) ratios in patients before and after ACL reconstruction (ACLR) using bone-patellar tendon grafts and to establish the relationships between HQ ratio and knee function.

METHODS

Forty-four patients (mean age of 26.6 years) underwent isokinetic testing of quadriceps and hamstring muscles before and after ACLR and HQ ratios were calculated. Lysholm, IKDC and Cincinnati Scores were used to assess function. Isokinetic concentric and eccentric peak torque (Nm/kg) was measured at three different speeds: 60, 120, and 180°/s. Isometric strength was tested at 30° and 60° of knee flexion.

RESULTS

For the isometric tests, the HQ ratio between the involved and non-involved limb was not different for the ACLD knee (p = 0.28) at 30° knee flexion, but significant at the 60° flexion angle (p = 0.02) and for the ACLR knees at 30° and 60° (p = 0.02). For the isokinetic tests, the ratio between involved and non-involved limb was significant for ACL-deficient knees at both 60 (p = 0.039) and 120°/s (p = 0.05). There were significant differences between limbs for all speeds in ACLR knees (p = 0.0003-0.01). For the eccentric tests, the HQ ratio between the involved and non-involved limbs was not significant for both the ACLD (p = 0.19) and ACLR knees (p = 0.29) at the speed of 60°/s. At 120 and 180°/s, there were significant differences between limbs for both the ACLD (p = 0.02) and ACLR knees (p = 0.003). Linear regression did not reveal significant relationships between Cincinnati, Lysholm, and IKDC scores and HQ ratios in the ACLD (R² = 0.35, p = 0.58; R² = 0.34, p = 0.63; R² = 0.38, p = 0.49). In contrast, there were significant correlations between the Lysholm and IKDC scores and HQ ratios in the ACLR knees (R² = 0.84, p = 0.002; R² = 0.86, p = 0.001).

CONCLUSIONS

The findings of this study suggest that the HQ ratio in ACLD patients was not a predictor, but an indicator of patient-perceived knee function following ACLR.

LEVEL OF EVIDENCE

Level IV, case series.

Single-leg vertical jump test as a functional test after anterior cruciate ligament reconstruction

BACKGROUND

The aim of this study was to identify the correlations between the single-leg vertical jump (SLVJ) test and subjective and objective tests which were used widely for determining return-to-sports (RTS) after anterior cruciate ligament reconstruction (ACLR).

METHODS

Seventy-five patients (29.5 ± 9.2 years) who underwent ACLR between May 2012 and Jan 2014 were included. Subjective knee scoring systems including subjective International Knee Documentation Committee (IKDC) score, Lysholm score, Tegner activity scale, and ACL-Return to Sports after Injury (ACL-RSI) scale were assessed. Objective tests were also performed.

RESULTS

The limb symmetry index (LSI) for SLVJ test and single-leg hop for distance (SLHD) test was 89.4 ± 14.9% and 90.7 ± 11.7%. LSI for SLVJ test was correlated to subjective IKDC scores (r = 0.26, P = 0.024), Tegner activity scale (r = 0.64, P < 0.001), ACL-RSI scale (r = 0.61, P < 0.001), LSI for SLHD (r = 0.45, P < 0.001), Co-contraction (r = -0.57, P < 0.001), Shuttle run (r = -0.52, P < 0.001), and Carioca (r = -0.54, P < 0.001) tests. In isokinetic strength tests, extensor peak torque (r = 0.30, P = 0.009) and extensor strength deficit (r = -0.41, P < 0.001) were correlated with LSI for SLVJ test.

CONCLUSION

There were considerable correlations between SLVJ test and subjective IKDC scores, Tegner activity scale, ACL-RSI scale, isokinetic extensor muscle strength, and all other functional tests. SLVJ test could be used conveniently to determine RTS after ACLR in outpatient clinics.

LEVEL OF EVIDENCE

Level IV, case series.

Improvements in Thigh Strength Symmetry Are Modestly Correlated With Changes in Self-Reported Function After Anterior Cruciate Ligament Reconstruction

Background:

The association between quadriceps strength and functional outcomes after anterior cruciate ligament reconstruction (ACLR) is a focus of current research, while evaluations of hamstring strength are limited, despite the frequent use of hamstring autografts.

Purpose/Hypothesis:

The purpose of this study was to determine the relationship between changes in quadriceps and hamstring strength symmetry and self-reported outcomes before ACLR and at 12 and 24 weeks after surgery. We hypothesized that improvements in quadriceps and hamstring strength symmetry would be correlated with improvements in self-reported outcome measures within the first 6 months after ACLR.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

Thirty patients who underwent ACLR with a hamstring autograft were enrolled. Quadriceps and hamstring strength and Knee injury and Osteoarthritis Outcome Score (KOOS) values were assessed before and at 12 and 24 weeks after ACLR; limb symmetry indexes for strength were calculated at each time point. The Friedman and Wilcoxon signed-rank tests were used to analyze changes in KOOS values over time. Spearman rank-order correlations were used to test the relationship between changes in strength and KOOS values between each time point.

Results:

Hamstring and quadriceps limb symmetry significantly increased with time (P ≤ .03). Fair correlations were observed between changes in the hamstring index and changes in the KOOS Symptoms subscore from before surgery to 12 weeks postoperatively (r = 0.48; P ≤ .05). Changes in the quadriceps index (QI) were moderately correlated with changes in the KOOS Sport/Recreation subscore (r = 0.60; P = .001), and fair correlations were seen between the QI and the KOOS Quality of Life subscore (r = 0.39; P ≤ .04) from preoperatively to 12 weeks after surgery. Moderate correlations were seen between the QI and the KOOS Sport/Recreation subscore (r = 0.57; P = .005) from 12 to 24 weeks after surgery.

Conclusion:

Improvements in quadriceps and hamstring strength symmetry were modestly associated with improvements in athletes’ perceived function in the first 6 months after ACLR. Specifically, improvements in hamstring symmetry were associated with improvements in knee symptoms within the first 12 weeks postoperatively, while improvements in quadriceps symmetry were associated with improvements in self-reported sport function throughout the first 6 months after ACLR. The restoration of strength symmetry within the first 6 months may be a critical component of rehabilitation aimed at maximizing function after ACLR. Further investigation is warranted to comprehensively evaluate whether the timing of strength gains predicts future function, including those who successfully return to their preinjury activity level after ACLR.

Dynamic balance asymmetries in pre-season injury-prevention screening in healthy young soccer players using the Modified Star Excursion Balance Test-a pilot study

[Purpose] The purpose of this preliminary study was to investigate whether young players with no history of injury, have developed early asymmetries in dynamic balance ability tested via the recommended for screening in sports, Modified Star Excursion Balance Test (MSEBT). [Participants and Methods] Twenty-four young healthy male soccer players participated in the study having at least 4 years of systematic soccer training. The Waterloo Footedness Questionnaire was used to discriminate the stability dominant leg (STAB) from the non-stability dominant leg (NSTAB). Dynamic balance was assessed via the MSEBT. Participants, after familiarization, made 3 attempts in each direction for both legs: a) Anterior (AN), b) Posterolateral (PL) and c) Posteromedial (PM). [Results] The sole statistically significant performance asymmetry was in the PL direction, in favor of the STAB (94.5 ± 13.3 cm vs. 98.1 ± 10.4 cm). [Conclusion] The results of this pilot study showed a potential for developing dynamic balance asymmetries, in soccer players at the age of 13–14 years. Since asymmetry was significant in only one direction, further long term monitoring would be helpful to evaluate whether this is a growing functional deficit, potentially involving any of the other two directions of testing or if it is alleviated with increasing training age. These asymmetries could comprise an injury risk factor.

A comparison of lower limb muscle activation pattern using voluntary response index between pronated and normal foot structures during forward jump landing

BACKGROUND

Pronated of the foot is one of the important factors contributing to musculoskeletal problems affecting the lower extremities. It is known that in a pronated foot, excessive mechanical load is applied to the lower limb structures which may result in altered biomechanics and muscle activation patterns. The aim of this study was to determine changes in the muscle activation pattern of the lower extremities in individuals with pronated, compared to normal, feet, using the voluntary response index (VRI).

METHODS

In this cross sectional study, 15 asymptomatic pronated foot individuals (mean age 23.27 ± 3.28 years) and 15 normal subjects (mean age 23.40 ± 3.11 years) were recruited by simple non-random sampling. Electrical activities of gluteus medius (GM), vastus lateralis (VL), vastus medialis (VM), biceps femoris, semitendinosus (ST), and medial gastrocnemius (MG) muscles were recorded during a forward jump landing task. Voluntary response index (VRI) variables, included similarity index (SI) and magnitude (Mag) were also evaluated.

RESULTS

Muscle activity of VM (p < 0.001) and ST (p = 0.010) were significantly higher but VL (p = 0.039) and MG (p = 0.001) were significantly lower in pronated foot, compared to normal subjects. Similarity index was found to be different (p < 0.001) between pronated foot and healthy individuals. No significant difference was found in terms of Mag between the two groups (p = 0.576).

CONCLUSION

The altered pattern of lower limb muscle activation identified in the pronated foot during landing may be attributed to the different activation involving VL, VM, MG and ST muscles. Adaptations to the biomechanical effects, due to the pronated foot causing altered activation of VL, VM, MG, and ST muscles, results in an altered pattern of muscle activation. This change in activation pattern may harm the effectiveness of movement control processes; and might also predispose individuals with pronated feet, to injuries. It seems that an altered motor strategy with the aim of minimizing biomechanical changes, predisposes individuals to injuries. However, further large scale studies are needed to support the findings of the present study.

Refractory patellar tendinopathy treated by arthroscopic decortication of the inferior patellar pole in athletes: Mid-term outcomes

BACKGROUND

This study aimed to evaluate the clinical outcomes of arthroscopic decortication of the inferior patellar pole in athletes with refractory chronic patellar tendinopathy.

METHODS

Thirty-seven athletes in whom conservative management for at least six months failed underwent arthroscopic patellar tendon debridement and decortication of the inferior pole of the patella. Clinical outcomes were evaluated using subjective knee scores and isokinetic muscle strength tests. The average duration taken and sports participation level were also assessed.

RESULTS

The mean follow-up period was 51.3 ± 14.8 months. At the last follow-up, all improvements in subjective knee scores including Lysholm score, International Knee Documentation Committee (IKDC) subjective score, Victorian Institute of Sport Assessment -Patella (VISA-P) score, and Kujala score were statistically significant (p<.001). Tegner activity scale improved from 6.5±1.0 to 8.9±0.8 (p<.001). Limb symmetry index for extensor peak torque improved from 71.4±19.6% to 92.7±21.7% (p<.001). Thirty-two (86.5 %) athletes were able to return to full sports activities in a mean 3.5±1.7months, and 27 (73%) athletes maintained their previous sports activity level at the last follow-up. Symptoms recurred in two (5.2%).

CONCLUSIONS

Arthroscopic decortication of the inferior pole of the patella showed satisfactory clinical results and high rates of return to sports at mid-term follow-up in professional athletes with refractory chronic patellar tendinopathy. This technique could be an invasive, safe, and effective treatment for chronic patellar tendinopathy in professional athletes who want a faster return to sports.

LEVEL OF EVIDENCE

Level IV, case series.

Knee isokinetic performance following anterior cruciate ligament reconstruction: patellar tendon versus hamstrings graft

OBJECTIVE

To compare knee isokinetic performance six months after reconstruction of the anterior cruciate ligament using grafts from either the patellar tendon or the hamstrings among patients who underwent the same rehabilitation protocol.

METHODS

Thirty-four patients were evaluated (17 with grafts from the patellar tendon and 17 with grafts from the hamstrings). Operated and non-operated knees were compared with regards to the variables of peak torque, work and the hamstring/quadriceps relationship at velocities of 60º/s and 180º/s and power of 180º/s after six months of surgery.

RESULTS

The patients with ACL reconstruction using the patellar tendon (BPTB) showed quadriceps deficits for all variables, but the flexor musculature was balanced. In the hamstring group, both the extensors and the flexors showed deficits for the variables analyzed, except for hamstring power at 180º/s.

CONCLUSION

Patients in the patellar tendon group had a greater quadriceps deficit compared with those in the hamstrings group. Patients in the hamstrings group had a greater muscular deficit in the flexor mechanism compared with the contralateral knee. An unbalanced H/Q ratio was observed regardless of graft type, but this was more evident in the BPTB group.

Higher hamstring-to-quadriceps isokinetic strength ratio during the first post-operative months in patients with quadriceps tendon compared to hamstring tendon graft following ACL reconstruction

PURPOSE

The aim of this study was to compare isokinetic quadriceps and hamstring muscle strength in patients following anterior cruciate ligament (ACL) reconstruction who received either hamstring (HT) or quadriceps (QT) tendon autografts at two time intervals within the first year after surgery.

METHODS

One hundred twenty-four patients, 81 males (age 22.0 ± 6.2 years) and 43 females (age 20.9 ± 8.7 years), participated in this study. ACL reconstruction was performed with either quadriceps tendon autografts (QT; n = 61) or hamstring tendon autografts (HT; n = 63). Two isokinetic muscle strength tests (t1: 5.5 ± 1.2 months; t2: 7.6 ± 1.6 months) were performed at an angular velocity of 60°/s in both the injured and contralateral knees. An independent t test as well as a two-factor analysis of variance with repeated measurements was used. The significance level was set at p < 0.05.

RESULTS

A statistically significant lower knee extensor strength was observed in the QT group within one year after surgery (p < 0.001). Additionally, data showed a significant higher H/Q ratio in QT patients compared to the HT group at t1 (p < 0.001) and t2 (p = 0.001) as well as a significant effect over time (p < 0.001) and interaction effect of time and graft (p = 0.007). Side-to-side values for extensor muscle strength were significantly (p < 0.001) greater in HT graft patients, while QT patients showed significantly (p < 0.001) greater values for flexor muscle strength at both time points of isokinetic testing, respectively.

CONCLUSION

The results of this study indicate that graft choice has an impact on extensor strength in the first months after ACL reconstruction; however, there is no impact on flexor strength. The finding of a higher H/Q ratio in patients with QT grafts within the first months following surgery is possibly of clinical relevance. This may potentially be associated with lower stress on the maturing ACL graft. Furthermore, normal thigh strength can be restored over time.

LEVEL OF EVIDENCE

III.

Isokinetic angle-specific moments and ratios characterizing hamstring and quadriceps strength in anterior cruciate ligament deficient knees

This study is intended to find more effective and robust clinical diagnostic indices to characterize muscle strength and coordination alternation following anterior cruciate ligament (ACL) rupture. To evaluate angle-specific moments and hamstring (H)/quadriceps (Q) ratios, 46 male subjects with unilateral chronic ACL-rupture performed isokinetic concentric (c), eccentric (e) quadriceps and hamstring muscle tests respectively at 60°/s. Normalized moments and H/Q ratios were calculated for peak moment (PM) and 30°, 40°, 50°, 60°, 70°, 80° knee flexion angles. Furthermore, we introduced single-to-arithmetic-mean (SAM) and single-to-root-mean-square (SRMS) muscle co-contraction ratios, calculating them for specific angles and different contraction repetitions. Normalized PM and 40° specific concentric quadriceps, concentric hamstring strength in the ACL-deficient knee were reduced significantly (P ≤ 0.05). Concentric angle-specific moments together with Qe/Qc ratios at 40° (d = 0.766 vs. d = 0.654) identify more obvious differences than peak values in ACL ruptured limbs. Furthermore, we found SRMS-QeQc deficits at 40° showed stronger effect than Qe/Qc ratios (d = 0.918 vs. d = 0.766), albeit other ratio differences remained basically the same effect size as the original H/Q ratios. All the newly defined SAM and SRMS indices could decrease variance. Overall, 40° knee moments and SAM/SRMS ratios might be new potential diagnosis indices for ACL rupture detection.

Mapping current research trends on neuromuscular risk factors of non-contact ACL injury

The aim of this systematic review was (i) to identify neuromuscular markers that have been predictive of a primary non-contact ACL injury, (ii) to assess whether proposed risk factors have been supported or refuted in the literature from cohort and case-control studies, and (iii) to reflect on the body of research that aims at developing field based tools to assess risk through an association with these risk factors. Electronic searches were undertaken, of PubMed, SCOPUS, Web of Science, CINAHL and SPORTDiscus examining neuromuscular risk factors associated with ACL injury published between January 1990 and July 2015. The evidence supporting neuromuscular risk factors of ACL injury is limited where only 4 prospective cohort studies were found. Three of which looked into muscular capacity and one looked into muscular activation patterns but none of the studies found strong evidence of how muscular capacity or muscular activation deficits are a risk factor for a primary non-contact ACL injury. A number of factors associated to neural control and muscular capacity have been suggested to be related to non-contact ACL injury risk but the level of evidence supporting these risk factors remains often elusive, leaving researchers and practitioners uncertain when developing evidence-based injury prevention programs.

Biomechanical and neuromuscular characteristics of male athletes: implications for the development of anterior cruciate ligament injury prevention programs

Prevention of anterior cruciate ligament (ACL) injury is likely the most effective strategy to reduce undesired health consequences including reconstruction surgery, long-term rehabilitation, and pre-mature osteoarthritis occurrence. A thorough understanding of mechanisms and risk factors of ACL injury is crucial to develop effective prevention programs, especially for biomechanical and neuromuscular modifiable risk factors. Historically, the available evidence regarding ACL risk factors has mainly involved female athletes or has compared male and female athletes without an intra-group comparison for male athletes. Therefore, the principal purpose of this article was to review existing evidence regarding the investigation of biomechanical and neuromuscular characteristics that may imply aberrant knee kinematics and kinetics that would place the male athlete at risk of ACL injury. Biomechanical evidence related to knee kinematics and kinetics was reviewed by different planes (sagittal and frontal/coronal), tasks (single-leg landing and cutting), situation (anticipated and unanticipated), foot positioning, playing surface, and fatigued status. Neuromuscular evidence potentially related to ACL injury was reviewed. Recommendations for prevention programs for ACL injuries in male athletes were developed based on the synthesis of the biomechanical and neuromuscular characteristics. The recommendations suggest performing exercises with multi-plane biomechanical components including single-leg maneuvers in dynamic movements, reaction to and decision making in unexpected situations, appropriate foot positioning, and consideration of playing surface condition, as well as enhancing neuromuscular aspects such as fatigue, proprioception, muscle activation, and inter-joint coordination.

Influence of Anterior Cruciate Ligament Tear on Thigh Muscle Strength and Hamstring-to-Quadriceps Ratio: A Meta-Analysis

Theoretical compensation after anterior cruciate ligament (ACL) tear could cause quadriceps weakness and hamstring activation, preventing anterior tibial subluxation and affecting the expected hamstring-to-quadriceps ratio. Although quadriceps weakness often occurs after ACL tears, it remains unclear whether hamstring strength and hamstring-to-quadriceps ratio increase in ACL deficient knees. This meta-analysis compared the isokinetic muscle strength of quadriceps and hamstring muscles, and the hamstring-to-quadriceps ratio, of the injured and injured limbs of patients with ACL tears. This meta-analysis included all studies comparing isokinetic thigh muscle strengths and hamstring-to-quadriceps ratio in the injured and uninjured legs of patients with ACL tear, without or before surgery. Thirteen studies were included in the meta-analysis. Quadriceps and hamstring strengths were 22.3 N∙m (95% CI: 15.2 to 29.3 N∙m; P<0.001) and 7.4 N∙m (95% CI: 4.3 to 10.5 N∙m; P<0.001) lower, respectively, on the injured than on the uninjured side. The mean hamstring-to-quadriceps ratio was 4% greater in ACL deficient than in uninjured limbs (95% CI: 1.7% to 6.3%; P<0.001). Conclusively, Decreases were observed in both the quadriceps and hamstring muscles of patients with ACL tear, with the decrease in quadriceps strength being 3-fold greater. These uneven reductions slightly increase the hamstring-to-quadriceps ratio in ACL deficient knees.

Correlation between Quadriceps Endurance and Adduction Moment in Medial Knee Osteoarthritis

It is not clear whether the strength or endurance of thigh muscles (quadriceps and hamstring) is positively or negatively correlated with the adduction moment of osteoarthritic knees. This study therefore assessed the relationships between the strength and endurance of the quadriceps and hamstring muscles and adduction moment in osteoarthritic knees and evaluated predictors of the adduction moment. The study cohort comprised 35 patients with unilateral medial osteoarthritis and varus deformity who were candidates for open wedge osteotomy. The maximal torque (60°/sec) and total work (180°/sec) of the quadriceps and hamstring muscles and knee adduction moment were evaluated using an isokinetic testing device and gait analysis system. The total work of the quadriceps (r = 0.429, P = 0.037) and hamstring (r = 0.426, P = 0.045) muscles at 180°/sec each correlated with knee adduction moment. Preoperative varus deformity was positively correlated with adduction moment (r = 0.421, P = 0.041). Multiple linear regression analysis showed that quadriceps endurance at 180°/sec was the only factor independently associated with adduction moment (β = 0.790, P = 0.032). The adduction moment of osteoarthritic knees correlated with the endurance, but not the strength, of the quadriceps muscle. However, knee adduction moment did not correlate with the strength or endurance of the hamstring muscle.

Concurrent assessments of lower limb loading patterns, mechanical muscle strength and functional performance in ACL-patients--a cross-sectional study

BACKGROUND

Full recovery in muscle strength and functional performance may not be achieved after ACL-injury.

AIM

The aim of this study is to investigate loading patterns during jumping, muscle function and functional performance in ACL-reconstructed patients and to investigate the origin of between-limb asymmetry by means of a 3-dimensional movement analysis. Design is cross-sectional.

METHODS

23 ACL-reconstructed men (27.2±7.5 years, BMI: 25.4±3.2) 27±7 month post-surgery and 25 matched controls (27.2±5.4 years, BMI: 24.1±1.8) were included. Participants performed (i) bilateral and (ii) unilateral counter movement jumps (CMJ). A 3-D movement analysis was performed by a six-camera Vicon MX-system. Subsequently, jump height (JH), knee joint range of motion (ROM), peak and mean sagittal knee moments were analyzed (iii) one-leg maximal jump for distance was performed, and (iv) maximal unilateral isometric knee extensor and flexor strength (MVC) were measured using stabilized dynamometry.

RESULTS

No in-between group differences in age or BMI were observed. CMJ: Between-limb asymmetry ratios for ROM differed (p<0.01) between patients and controls in both types of CMJ (96.1% vs. 102.6% and 87.0% vs. 99.9% in bilateral and single-leg CMJs, respectively). Jump for distance: Patients demonstrated greater (p<0.01) asymmetry for jump length (92.9% vs. 98.6%). MVC: Asymmetry in hamstring MVC was greater (p<0.001) for patients than controls (77.4% vs. 101.3%).

CONCLUSIONS

ACL-patients showed reduced function of the operated leg~2 years post ACL-reconstruction, especially for hamstring MVC. Hamstrings are important protagonists to the ACL, thus representing a potential risk factor for secondary ACL-rupture and/or osteoarthritis.

Functional performance tests as indicators of returning to sports after anterior cruciate ligament reconstruction

BACKGROUND

There is a lack of standardized objective criteria to accurately assess the ability of a patient to progress through the end stages of rehabilitation and safely return to their previous level of athletic activity after anterior cruciate ligament (ACL) reconstruction.

PURPOSE

To determine objective factors involved in returning to sports following ACL reconstruction.

METHODS

Based on our inclusion criteria of a minimum 2-year follow-up, pre-injury sports activity level of Tegner 5 or greater, we retrospectively evaluated 67 patients who underwent ACL reconstruction. The patients were divided into "return-to-sports" (n=51) and "non-return" groups (n=16) by surveying participants using a questionnaire. Comparisons between the two groups were made using pre-operative and post-operative International Knee Documentation Committee questionnaires (IKDC), Lysholm score, and KT-2000 arthrometer. Flexor and extensor muscle strength, and functional performance tests (one-leg-hop test, co-contraction, shuttle run, and carioca tests) were used for assessment.

RESULTS

Overall clinical results, including IKDC score, Lysholm score, and KT-2000 arthrometer, improved in all patients post-operatively and no significant difference was seen between the two groups (P>0.05). Although there was no significant difference in flexor or extensor deficits, one-leg-hop test, or shuttle run test, "return-to-sports" group obtained significantly better scores in the co-contraction and carioca tests (P<0.05).

CONCLUSIONS

Tests that assess rotational stability showed statistically significant differences between the two groups. Further prospective studies with larger cohort are needed to determine the factors associated with returning to sports after ACL reconstruction.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

Principal component modeling of isokinetic moment curves for discriminating between the injured and healthy knees of unilateral ACL deficient patients

Bilateral knee strength evaluations of unilateral anterior cruciate ligament (ACL) deficient patients using isokinetic dynamometry are commonly performed in rehabilitation settings. The most frequently-used outcome measure is the peak moment value attained by the knee extensor and flexor muscle groups. However, other strength curve features may also be of clinical interest and utility. The purpose of this investigation was to identify, using Principal Component Analysis (PCA), strength curve features that explain the majority of variation between the injured and uninjured knee, and to assess the capabilities of these features to detect the presence of injury. A mixed gender cohort of 43 unilateral ACL deficient patients performed 6 continuous concentric knee extension and flexion repetitions bilaterally at 60°s(-1) and 180°s(-1) within a 90° range of motion. Moment waveforms were analyzed using PCA, and binary logistic regression was used to develop a discriminatory decision rule. For all directions and speeds, a statistically significant overall reduction in strength was noted for the involved knee in comparison to the uninvolved knee. The discriminatory decision rule yielded a specificity and sensitivity of 60.5% and 60.5%, respectively, corresponding to an accuracy of ∼62%. As such, the curve features extracted using PCA enabled only limited clinical usefulness in discerning between the ACL deficient and contra lateral, healthy knee. Improvement in discrimination capabilities may perhaps be achieved by consideration of different testing speeds and contraction modes, as well as utilization of other data analysis techniques.

Gait and neuromuscular asymmetries after acute anterior cruciate ligament rupture

The decreased internal knee extensor moment is a significant gait asymmetry among patients with anterior cruciate ligament (ACL) deficiency, yet the muscular strategy driving this altered moment for the injured limb is unclear.

PURPOSE

This study aimed to determine whether patients with ACL deficiency and characteristic knee instability would demonstrate normal extensor and increased flexor muscle force to generate a decreased internal extensor moment (i.e., use a hamstring facilitation strategy).

METHODS

Gait analysis was performed on 31 athletes with acute ACL rupture who exhibited characteristic knee instability after injury. Peak internal knee extensor moment was calculated using inverse dynamics, and muscle forces were estimated using an electromyography-driven modeling approach. Comparisons were made between the injured and contralateral limbs.

RESULTS

As expected, patients demonstrated decreased peak knee flexion (P = 0.028) and internal knee extensor moment (P = 0.0004) for their injured limb but exhibited neither an isolated decrease in extensor force (quadriceps avoidance) nor an isolated increase in flexor force (hamstring facilitation) at peak knee moment. Instead, they exhibited decreased muscle force from both flexor (P = 0.0001) and extensor (P = 0.0103) groups. This strategy of decreased muscle force may be explained in part by muscle weakness that frequently accompanies ACL injury or by apprehension, low confidence, and fear of further injury.

CONCLUSIONS

This is the first study to estimate muscle forces in the ACL-deficient knee using an electromyography-driven approach. These results affirm the existence of neuromuscular asymmetries in the individuals with ACL deficiency and characteristic knee instability.

Anterior cruciate ligament-deficient patients with passive knee joint laxity have a decreased range of anterior-posterior motion during active movements

BACKGROUND

Although instability of the knee joint is known to modify gait patterns, the amount that patients compensate for joint laxity during active movements remains unknown.

PURPOSE

By developing a novel technique to allow the assessment of tibiofemoral kinematics, this study aimed to elucidate the role of passive joint laxity on active tibiofemoral kinematics during walking.

STUDY DESIGN

Controlled laboratory study.

METHODS

Using motion capture, together with combinations of advanced techniques for assessing skeletal kinematics (including the symmetrical axis of rotation approach [SARA], symmetrical center of rotation estimation [SCoRE], and optimal common shape technique [OCST]), a novel noninvasive approach to evaluate dynamic tibiofemoral motion was demonstrated as both reproducible and repeatable. Passive and active anterior-posterior translations of the tibiofemoral joint were then examined in 13 patients with anterior cruciate ligament (ACL) ruptures that were confirmed by magnetic resonance imaging and compared with those in their healthy contralateral limbs.

RESULTS

Passive tibial anterior translation was significantly greater in the ACL-ruptured knees than in the contralateral healthy controls. However, the femora of the ACL-ruptured knees generally remained more posterior (~3 mm) relative to the tibia within a gait cycle of walking compared with the healthy limbs. Surprisingly, the mean range of tibiofemoral anterior-posterior translation over an entire gait cycle was significantly lower in ACL-ruptured knees than in the healthy joints (P = .026). A positive correlation was detected between passive laxity and active joint mobility, but with a consistent reduction in the range of tibiofemoral anterior-posterior translation of approximately 3 mm in the ACL-deficient knees.

CONCLUSION

It seems that either active stabilization of tibiofemoral kinematics or anterior subluxation of the tibia reduces joint translation in lax knees. This implies that either a muscular overcompensation mechanism or a physical limitation due to secondary passive stabilizers occurs within the joint and thus produces a situation that has a reduced range of active motion compared with knees with physiological stability.

CLINICAL RELEVANCE

The reduced range of active tibiofemoral translation suggests overloading of the passive structures in passively lax knees, either through excessive muscular action or joint subluxation, and could provide a plausible mechanism for explaining posttraumatic degeneration of cartilage in the joint.

The effect of anterior cruciate ligament rupture on the timing and amplitude of gastrocnemius muscle activation: a study of alterations in EMG measures and their relationship to knee joint stability

Changes in hamstring and quadriceps activity are well known in individuals with anterior cruciate ligament deficiency (ACLD) to potentially compensate for knee joint instability. However, few studies have explored gastrocnemius activity or its relationship to knee stability. The purpose of this study was therefore to examine the activation characteristics of medial gastrocnemius (MG) in ACLD subjects and relate any changes to knee joint laxity. Two subject cohorts were assessed: those with unilateral ACLD (n=15) and uninjured control subjects (n=11). Surface EMG of the left and right MG were recorded during a controlled single leg hop on each limb. Onset and offset of MG activation relative to take-off, during flight and landing were calculated as well as muscle activity (RMS). Passive antero-posterior knee laxity was measured with a KT1000 arthrometer during a maximal manual displacement test. Medial gastrocnemius activity on the injured side of ACLD participants demonstrated significantly prolonged activation in preparation to hop, minimal muscle inactivity prior to take-off, and increased duration of overall muscle activity when compared to the uninjured side and control subjects (p<0.05). Significant positive correlations were found between passive knee joint laxity and prolonged activation prior to knee bend. RMS of the muscle signal was not significantly different between limbs. Overall, MG on the ACLD side demonstrated longer activation, with minimal rest during the hop test, which may be an attempt to maintain knee stability. Furthermore, the strong relationship between knee laxity and prolonged muscle activation suggests that individuals with a loss of knee stability are more reliant on active control of the gastrocnemius muscle.

Relationships among tendon regeneration on MRI, flexor strength, and functional performance after anterior cruciate ligament reconstruction with hamstring autograft

BACKGROUND

There are numerous reports on hamstring tendon regeneration after harvest for anterior cruciate ligament (ACL) reconstruction. However, few studies have evaluated the relationships among the magnetic resonance imaging (MRI) findings of hamstring regeneration, muscle strength, and functional results.

PURPOSE

This study evaluates the correlations among the hamstring regeneration on MRI, flexor strength, and functional performance after hamstring tendon harvesting in ACL reconstruction.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

We enrolled 45 patients who underwent primary ACL reconstruction using hamstring tendon autografts and in whom flexor strength, functional performance, and preoperative and postoperative MRI results were evaluated at least 2 years postoperatively. Isokinetic flexion strength was tested in the standard and prone positions. We evaluated the differences in flexor strength and functional performance according to the number of regenerated tendons. The correlation between the MRI findings (the number of regenerated hamstring tendons and proximal shift of the musculotendinous junction) and the functional performance and flexor strength was analyzed.

RESULTS

The patients were divided into 3 groups according to the regeneration of the hamstring tendons on MRI: both semitendinosus and gracilis tendons regenerated (group SG), only 1 tendon regenerated (group O), and no tendon regenerated (group N). Significant differences were found in the flexor deficit between group N and groups SG and O on the standard and prone position isokinetic tests. There was a significant correlation (ρ = -.472) between the number of regenerated hamstring tendons and the carioca test result. The proximal shift significantly correlated with the flexor deficit in the prone position isokinetic test (semitendinosus, r = .449; gracilis, r = .366).

CONCLUSION

Hamstring tendons regenerated after harvest for ACL reconstruction in a high proportion of the patients. The flexor strength with both the standard and prone position isokinetic tests differed in the 3 groups. The number of regenerated hamstring tendons was significantly correlated with performance on the carioca test. Proximal shifting of the musculotendinous junction was significantly correlated with flexor deficit on the hyperflexion isokinetic test.

Tibial rotation under combined in vivo loading after single- and double-bundle anterior cruciate ligament reconstruction

PURPOSE

To evaluate in vivo the differences in tibial rotation between single- and double-bundle anterior cruciate ligament (ACL)-reconstructed knees under combined loading conditions.

METHODS

An 8-camera optoelectronic system and a force plate were used to collect kinematic and kinetic data from 14 patients with double-bundle ACL reconstruction, 14 patients with single-bundle reconstruction, 12 ACL-deficient subjects, and 12 healthy control individuals while performing 2 tasks. The first included walking, 60° pivoting, and stair ascending, and the second included stair descending, 60° pivoting, and walking. The 2 variables evaluated were the maximum range of internal-external tibial rotation and the maximum knee rotational moment.

RESULTS

Tibial rotation angles were not significantly different across the 4 groups (P = .331 and P = .851, respectively) or when side-to-side differences were compared within groups (P = .216 and P = .371, respectively) for the ascending and descending maneuvers, nor were rotational moments among the 4 groups (P = .418 and P = .290, respectively). Similarly, for the descending maneuver, the rotational moments were not significantly different between sides (P = .192). However, for the ascending maneuver, rotational moments of the affected sides were significantly lower by 20.5% and 18.7% compared with their intact counterparts in the single-bundle (P = .015) and double-bundle (P = .05) groups, respectively.

CONCLUSIONS

High-intensity activities combining stair ascending or descending with pivoting produce similar tibial rotation in single- and double-bundle ACL-reconstructed patients. During such maneuvers, the reconstructed knee may be subjected to significantly lower rotational loads compared with the intact knee.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

The effects of hamstring harvesting on outcomes in anterior cruciate ligament-reconstructed patients: a comparative study between hamstring-harvested and -unharvested patients

PURPOSE

The purpose of this study was to evaluate the effects of hamstring harvesting in patients after anterior cruciate ligament (ACL) reconstruction by comparing groups with and without hamstring harvesting.

METHODS

We evaluated the effect of hamstring harvesting in 73 consecutive patients who underwent ACL reconstruction: 39 patients whose hamstrings were harvested for autografts (group H) were compared with 34 patients who received allografts during the same time period (group C [control]). The cases and controls were compared by analyzing the following variables: age, height, weight, mean follow-up period, type of tissue used, and meniscal surgery. Outcomes were assessed by the Lysholm knee score, Tegner activity score, and KT-2000 side-to-side difference (MEDmetric, San Diego, CA), as well as functional performance tests. The flexor deficit and isokinetic peak torque for knee flexion were measured in the sitting position (0° to 90°), and the flexion torque at 90° was measured in the prone position (60° to 120°).

RESULTS

Although significant knee flexion weakness after ACL reconstruction was observed, a significantly greater knee flexor deficit was found in autograft patients than in allograft patients (P < .001). No differences were found between groups in terms of clinical and functional results regardless of hamstring harvesting. The performance of both study groups in all 4 functional tests were significantly correlated with flexor deficit in the sitting position (P < .05) but not in hyperflexion. Significant flexor deficits in both normal and hyperflexed positions were noted in both groups when compared with the unaffected knee (group H, P < .001; group C, P = .002).

CONCLUSIONS

These results indicate significant knee flexion weakness compared with the unaffected knee after ACL reconstruction regardless of hamstring harvesting. Moreover, the greater increase in knee flexor deficit in the hamstring-harvested group compared with the allograft group was statistically significant. However, clinical and functional outcomes were similar between the groups.

LEVEL OF EVIDENCE

Level III, case-control study.

Laboratory evaluation of the pivot-shift phenomenon with use of kinetic analysis: a preliminary study

BACKGROUND

Currently, a suitable and reliable noninvasive method to evaluate rotational stability in vivo in anterior cruciate ligament-deficient knees, particularly during sports movements, does not exist. We speculated that if there is a rotational instability, the patient would avoid reaching a high pivoting moment during pivoting activities as a defense mechanism, and that the ground reaction moment, as registered by dynamometric platforms, would be reduced. On the basis of this hypothesis, we developed a study using kinetic analysis to evaluate rotational stability under dynamic loading.

METHODS

Thirty recreationally active athletes, including fifteen healthy subjects and fifteen with an anterior cruciate ligament-deficient knee, were recruited for this study. Patients performed jumping with pivoting with internal tibial rotation and external tibial rotation on the dynamometric platform with both the healthy and the injured limb. The quantitative results were graphically plotted, and the following parameters were evaluated: loading moment, pivoting moment, torque amplitude, loading slope, pivoting slope, percentage of pivoting with load, loading impulse, pivoting impulse, and maximum body rotation angle.

RESULTS

There were no significant differences between the dominant and nondominant knees in the control group during the jumping with pivoting and external tibial rotation test with regard to the pivoting moment (p = 0.805), pivoting slope (p = 0.716), pivoting impulse 2 (p = 0.858), and pivoting impulse 3 (p = 0.873). In patients with a chronic tear of the anterior cruciate ligament, there was a significant decrease of the pivoting moment (p = 0.02), pivoting slope (p = 0.005), pivoting impulse 2 (p = 0.006), and pivoting impulse 3 (p = 0.035) during the jumping with pivoting and external tibial rotation test in the anterior cruciate ligament-deficient knee compared with the healthy, contralateral knee.

CONCLUSION

Kinetic analysis with use of a dynamic platform can objectively detect alterations of rotational stability in anterior cruciate ligament-deficient knees, which may allow this to be a useful research tool for evaluating treatment strategies in patients with anterior cruciate ligament injuries.

Morphology of hamstring torque-time curves following ACL injury and reconstruction: mechanisms and implications

The purposes of this study were (i) to examine the effects of anterior cruciate ligament (ACL) status on hamstring force steadiness, peak hamstring strength, quadriceps (antagonist) activation, and physical performance, and (ii) to evaluate the associations of physical performance with hamstring steadiness and hamstring strength. Thirteen subjects with unilateral deficiency of the ACL (ACLD), 39 matched subjects with unilateral reconstructed ACL (ACLR; n = 25 with bone-patella tendon-bone (ACLR-PT) graft and n = 14 with combined semitendinosus and gracilis tendon (ACLR-STGT) graft) and 33 control subjects participated. Each subject performed maximal-effort isokinetic knee flexion repetitions at 180° s(-1) with electromyography (EMG) electrodes attached to their medial and lateral quadriceps muscles. Physical performance was assessed using the single-limb long hop for distance. Wavelet-derived mean instantaneous frequency (Mif) of flexor torque-time curves was significantly (p < 0.05) higher (i.e., less smooth) in ACLR-STGT subjects compared to the ACLD, ACLR-PT and control subjects. No significant differences existed for peak hamstrings strength (i.e., peak torque produced) or quadriceps antagonist EMG activity. Positive correlations were identified between hamstrings force steadiness and quadriceps antagonist activity for ACLD (r =  0.797), ACLR-PT (r = 0.467), and ACLR-STGT (r = 0.628) subjects. For ACLR-STGT subjects, reduced hamstrings force steadiness associated with poorer long-hop performance (r = -0.695). Reduced steadiness amongst ACLR-STGT subjects may reflect motor output variability of the antagonist (i.e., quadriceps dyskinesia) and/or agonist musculature-a maladaptive feature which potentially contributes to poorer single-limb hop performance. Measures of hamstring force steadiness in combination with traditional measures of peak hamstring strength provide valuable clinical information regarding knee joint function following ACL injury/ACLR.

Stride-to-stride variability is altered during backward walking in anterior cruciate ligament deficient patients

BACKGROUND

Recently backward walking is used by physical therapists to strengthen the hamstring muscles and thus improve the function of the knee joint of anterior cruciate ligament deficient patients. The aim of this study was to examine the stride-to-stride variability of anterior cruciate ligament deficient patients during backward walking. The variation of how a motor behavior emerges in time is best captured by tools derived from nonlinear dynamics, for which the temporal sequence in a series of values is the facet of interest.

METHODS

Fifteen patients with unilateral anterior cruciate ligament deficiency and eleven healthy controls walked backwards at their self-selected speed on a treadmill while three-dimensional knee kinematics were collected (100 Hz). A nonlinear measure, the largest Lyapunov Exponent was calculated from the resulted knee joint flexion-extension data of both groups to assess the stride-to-stride variability.

FINDINGS

Both knees of the deficient patients exhibited significantly lower Lyapunov Exponent values as compared to the healthy control group revealing more rigid movement pattern. The intact knee of the deficient patients showed significantly lower Lyapunov Exponent values as compared to the deficient knee.

INTERPRETATION

Anterior cruciate ligament (ACL) deficiency leads to loss of optimal variability regardless of the walking direction (forwards in previous studies or backwards here) as compared to healthy individuals. This could imply diminished functional responsiveness to the environmental demands for both knees of ACL deficient patients which could result in the knees being more susceptible to injury.

ACL injury and reconstruction: Clinical related in vivo biomechanics

Several researchers including our group have shown that knee joint biomechanics are impaired after anterior cruciate ligament (ACL) injury, in terms of kinematics and neuromuscular control. Current ACL reconstruction techniques do not seem to fully restore these adaptations. Our research has demonstrated that after ACL reconstruction, excessive tibial rotation is still present in high-demanding activities that involve both anterior and rotational loading of the knee. These findings seem to persist regardless of the autograft selection for the ACL reconstruction. Our results also suggest an impairment of neuromuscular control after ACL reconstruction, although muscle strength may have been reinstated. These abnormal biomechanical patterns may lead to loading of cartilage areas, which are not commonly loaded in the healthy knee and longitudinally can lead to osteoarthritis. Muscle imbalance can also influence patients' optimal sports performance exposing them to increased possibility of knee re-injury. In this review, our recommendations point towards further experimental work with in vivo and in vitro studies, in order to assist in the development of new surgical procedures that could possibly replicate more closely the natural ACL anatomy and prevent future knee pathology.

Eversion and inversion muscle group peak torque in hyperpronated and normal individuals

BACKGROUND

Excessive subtalar pronation causes significant changes in the biomechanics of the lower leg, adversely influences proprioceptive feedback and neuromuscular reflex behavior and consequently, affects stability of the foot. However, the changes in muscle strength, caused by hyperpronation are unclear.

OBJECTIVES

The purpose of the present study was to compare the evertor and invertor peak torque between hyperpronated and normal individuals as well as between their dominant and non-dominant foot.

METHOD

20 healthy male participants volunteered for this study. Leg dominance was assessed on the basis of a questionnaire and navicular drop measurements were used to classify participants into two groups: hyperpronated (> or =10 mm) and normals (5-9 mm). Isokinetic concentric eversion and inversion muscle group strength was tested at 30 degrees and 120 degrees/s using the Con-Trex MJ isokinetic dynamometer.

RESULTS

In all cases, inversion peak torque was greater than eversion peak torque and declined with increasing angular velocity. No significant differences were found for inversion and eversion concentric strength at both speeds tested, neither between normal and hyperpronated individuals neither between their dominant and non-dominant foot.

CONCLUSIONS

These results indicate the need re-evaluation of navicular drop values in order to identify normal and abnormal subtalar pronation. The assessment of eccentric contractions is also proposed when examining invertors and evertors isokinetic strength.

Knee extension and flexion muscle power after anterior cruciate ligament reconstruction with patellar tendon graft or hamstring tendons graft: a cross-sectional comparison 3 years post surgery

Hamstring muscles play a major role in knee-joint stabilization after anterior cruciate ligament (ACL) injury. Weakness of the knee extensors after ACL reconstruction with patellar tendon (PT) graft, and in the knee flexors after reconstruction with hamstring tendons (HT) graft has been observed up to 2 years post surgery, but not later. In these studies, isokinetic muscle torque was used. However, muscle power has been suggested to be a more sensitive and sport-specific measures of strength. The aim was to study quadriceps and hamstring muscle power in patients with ACL injury treated with surgical reconstruction with PT or HT grafts at a mean of 3 years after surgery. Twenty subjects with PT and 16 subjects with HT grafts (mean age at follow up 30 years, range 20-39, 25% women), who were all included in a prospective study and followed the same goal-based rehabilitation protocol for at least 4 months, were assessed with reliable, valid, and responsive tests of quadriceps and hamstring muscle power at 3 years (SD 0.9, range 2-5) after surgery. The mean difference between legs (injured minus uninjured), the hamstring to quadriceps (H:Q, hamstring divided by quadriceps) ratio, and the limb symmetry index (LSI, injured leg divided by uninjured and multiplied by 100) value, were used for comparisons between the groups (analysis of variance). The mean difference between the injured and uninjured legs was greater in the HT than in the PT group for knee flexion power (-21.3 vs. 7.7 W, p = 0.001). Patients with HT graft had lower H:Q ratio in the injured leg than the patients with PT graft (0.63 vs. 0.77, p = 0.012). They also had lower LSI for knee flexion power than those in the PT group (88 vs. 106%, p < 0.001). No differences were found between the groups for knee extension power. The lower hamstring muscle power, and the lower hamstring to quadriceps ratio in the HT graft group than in the PT graft group 3 years (range 2-5) after ACL reconstruction, reflect imbalance of knee muscles after reconstruction with HT graft that may have a negative effect on dynamic knee-joint stabilization.

Prevenção de lesões do ligamento cruzado anterior em futebolistas

A lesão do joelho é a mais comum entre as lesões graves apresentadas por futebolistas, destacando-se o ligamento cruzado anterior como um dos ligamentos do joelho mais frequentemente lesados. Assim, a prevenção de lesões do ligamento cruzado anterior em futebolistas deve ser encarada como uma preocupação constante para todos os agentes ligados à modalidade, independentemente do nível competitivo, idade e sexo dos praticantes. OBJETIVOS: O objetivo deste trabalho é a análise da importância do trabalho de prevenção de lesões do LCA em futebolistas que possa ser incorporado no treino de futebol. METODOLOGIA: A metodologia utilizada neste trabalho foi uma revisão da literatura. CONCLUSÕES: Propõe-se um programa de prevenção de lesões do ligamento cruzado anterior em futebolistas, com três sessões de treino semanais, englobando treino neuromuscular e treino proprioceptivo.

Clinically assessed knee joint laxity as a predictor for reconstruction after an anterior cruciate ligament injury: a prospective study of 100 patients treated with activity modification and rehabilitation

BACKGROUND

The association of early knee joint laxity with the need for later reconstruction of the anterior cruciate ligament has not been extensively studied.

HYPOTHESIS

The grade of knee laxity can be used as an early predictor of the need for later reconstruction.

STUDY DESIGN

Cohort study (prognosis); Level of evidence, 2.

METHODS

One hundred consecutive patients with an acute arthroscopically verified total anterior cruciate ligament rupture were followed prospectively for 15 years. Lachman and pivot-shift tests were performed with the patient under general anesthesia before arthroscopy. After 3 months, the tests were repeated in an ordinary clinical setting. All patients underwent rehabilitation as the first choice of treatment. Anterior cruciate ligament reconstruction was performed only in cases of significant reinjuries (n = 16) or reparable meniscal lesions (n = 6) at a mean of 4 years after injury (range, 4 months-11 years). After 15 years, 94 patients were available for follow-up.

RESULTS

Of the later reconstructed patients (n = 18), 82% had a high-grade Lachman test under anesthesia compared with 63% of the nonreconstructed patients (n = 45; P = .048). At 3 months, 44% of the nonreconstructed patients (n = 32) had a high-grade Lachman test compared with 82% of the reconstructed patients (n = 18; P = .007). Twenty-five patients displayed a normal pivot-shift test at 3 months, of whom 1 underwent later reconstruction (P = .009). A high-grade pivot-shift test at 3 months was associated with an 11.4 relative risk for reconstruction.

CONCLUSION

A positive pivot-shift test at 3 months after injury in an awake patient is the strongest predictor for the future need for reconstruction. Furthermore, a normal pivot-shift test at 3 months indicates a low risk for reconstruction and is characteristic for copers.

Submaximal fatigue of the hamstrings impairs specific reflex components and knee stability

Rupture of the anterior cruciate ligament (ACL) is one of the most serious sports-related injuries and requires long recovery time. The quadriceps and hamstring muscles are functionally important to control stability of the knee joint complex. Fatigue, however, is an important factor that may influence stabilizing control and thus cause ACL injuries. The objective of this study was therefore to assess how submaximal fatigue exercises of the hamstring muscles affect anterior tibial translation as a direct measure of knee joint stability. While 15 test participants were standing upright with the knees in 30 degrees of flexion, anterior tibial translation was induced by a force of 315 N. Two linear potentiometers placed on the tibial tuberosity and the patella recorded tibial motion relative to the femur. Reflex latencies and neuromuscular hamstring activity were determined using surface electromyography (EMG). Muscle fatigue produced a significant longer latency for the monosynaptic reflex latencies, whereas no differences in the latencies of the medium latency component were found. Fatigue significantly reduced EMG amplitudes of the short and medium latency components. These alterations were in line with significantly increased anterior tibial translation. Our results suggest that hamstring fatigue is effectively associated with mechanical loss of knee stability. This decrease in joint stability may at least in part explain higher risk of ACL injury, especially in fatigued muscles. Furthermore, we discuss why the present findings indicate that reduced motor activity rather than the extended latency of the first hamstring response is the reason for possible failure.

Tibial Rotation in Anterior Cruciate Ligament (ACL)-Deficient and ACL-Reconstructed Knees

Excessive tibial rotation has been documented in anterior cruciate ligament (ACL) deficiency during walking. ACL reconstruction has been unable to correct this abnormality in activities that are more demanding than walking and involve both anterior and rotational loading of the knee. These findings persist regardless of graft selection for the ACL reconstruction (bone-patellar tendon-bone or semitendinosus gracilis). Based on this research work, we propose a theoretical perspective for the development of osteoarthritis in both the ACL-deficient and the ACL-reconstructed knee. We propose that excessive tibial rotation will lead to abnormal loading of the cartilage areas that are not commonly loaded in the healthy knee. Over time, this abnormal loading will lead to osteoarthritis. We hypothesise that the development of new surgical procedures and grafts, such as a more horizontally oriented femoral tunnel or a double-bundle ACL reconstruction, could possibly restore tibial rotation to normal levels and prevent future knee pathology. However, in vivo gait analysis studies are needed to examine the effects of these surgical procedures on tibial rotation. Prospective in vivo and in vitro studies are also necessary to verify or refute our theoretical proposition for the development of osteoarthritis.

Functional assessment and muscle strength before and after reconstruction of chronic anterior cruciate ligament lesions

PURPOSE

The goal of this study was to evaluate strength and functional capacity before and after anterior cruciate ligament (ACL) reconstruction to determine the influences of preoperative strength deficit, graft type, and gender, as well as their clinical relevance in predicting postsurgical recovery and determining the postoperative rehabilitation program.

METHODS

This was a retrospective review of prospectively collected uniform data from a group of 191 patients undergoing ACL reconstruction. We assessed functional capabilities and strength of the quadriceps and hamstring at 60 degrees/s and 180 degrees/s by use of a Cybex II dynamometer (Lumex, Ronkonkoma, NY) before and 6, 9, and 12 months after surgery.

RESULTS

There was a preoperative quadriceps strength deficit and a decreased limb symmetry index in patients with an ACL deficiency. This strength deficit increased postoperatively, with the highest measured deficit occurring at 6 months postoperatively and a clear improvement from 6 to 12 months. Functional assessment showed identical development. There was a statistically significant relation between an increased quadriceps strength deficit preoperatively and poor early postoperative functional performance. For the bone-patellar tendon-bone (BPTB) group, there was an increased quadriceps strength deficit compared with the semitendinosus and gracilis tendon (STG) group, and the STG group had an increased hamstring strength deficit on postoperative testing. The postoperative hamstring strength deficit is significantly increased in female patients.

CONCLUSIONS

All of these data suggest that quadriceps strength deficit is related to the ACL injury and is increased by ACL reconstruction. Even 1 year after ACL reconstruction, a quadriceps strength deficit of almost 20% persists. Flexion strength is within the normal range before and after surgery. These results are influenced by graft choice, with a higher quadriceps strength deficit for BPTB grafts. STG grafts induce a higher hamstring strength deficit compared with BPTB grafts. Functional assessment is improved at 9 and 12 months postoperatively compared with preoperatively regardless of graft type. However, an increased preoperative quadriceps strength deficit results in a lower limb symmetry index at 6 and 9 months postoperatively.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Knee joint mechanics under quadriceps--hamstrings muscle forces are influenced by tibial restraint

BACKGROUND

To investigate the role of quadriceps and hamstrings muscle recruitments on knee joint mechanics, measurement studies constrain the tibial anterior-posterior translation at a point away from the joint. This generates a restraining force perpendicular to the tibia thus introducing an artefact shear force that likely alters joint mechanics and forces in cruciate ligaments.

METHODS

A 3D nonlinear finite element model of the entire knee joint, including tibiofemoral and patellofemoral joints, was used to investigate joint mechanics in flexion (0 degrees -90 degrees ) under isolated and combined hamstrings and quadriceps activation. The effect of tibial restraint at two locations on results was studied and compared with the reference boundary condition of tibia constrained by pure moments.

FINDINGS

Tibial restraint by a force rather than a pure moment substantially influences the joint response. For identical forces, hamstrings have much greater moment generating capacity at larger flexion angles while quadriceps are more effective at smaller angles.

INTERPRETATION

Tibial constraint by a restraining force rather than a pure moment causes an artefact force on the joint that vary with muscle forces and restraining location. These artefact shear forces, especially when placed closer to the joint, considerably reduce forces in cruciate ligaments; in anterior cruciate ligament at near full extension and in posterior cruciate ligament at larger flexion angles. The beneficial effects of muscle co-contraction in reducing anterior cruciate ligament forces at near full extension and in posterior cruciate ligament forces at near 90 degrees , however, disappear as the restraint on the tibia approaches the joint. The artefact forces could distort results and their interpretations.

Thigh muscle weakness in ACL-deficient knees persists without structured rehabilitation

We evaluated whether quadriceps and hamstrings weakness depended on chronicity in amateur athletes with anterior cruciate ligament deficiencies. We hypothesized that the weakness would not recover to the level of healthy control subjects without structured rehabilitation. Secondarily, we asked whether quadriceps and hamstrings side-to-side percent asymmetry in strength was consistent at different stages of chronicity. Thirty-six male amateur athletes forming equal groups of short, intermediate, and long chronicity (mean, 4, 12, and 56 months, respectively) were tested isokinetically against control subjects at 60 degrees per second. Weakness was substantial in both muscle groups and at all times ranging from 32% to 21% compared with the control subjects. However, side-to-side deficits revealed a linear trend of lessening with time. The quadriceps had greater side-to-side asymmetry that ranged from 23% to 10%, whereas the hamstrings asymmetry ranged from 14% to almost 0%. Acquiring symmetric strength earlier than 1 year after injury only occurred in the hamstrings. It can be inferred that participation in organized rehabilitation would minimize the detrimental effects of anterior cruciate ligament rupture on thigh muscle strength.

LEVEL OF EVIDENCE

Prognostic Study, Level II.