Patellar cartilage increase following ACL reconstruction with and without meniscal pathology: a two-year prospective MRI morphological study.

BACKGROUND: Anterior cruciate ligament reconstruction (ACLR) together with concomitant meniscal injury are risk factors for the development of tibiofemoral (TF) osteoarthritis (OA), but the potential effect on the patellofemoral (PF) joint is unclear. The aim of this study was to: (i) investigate change in patellar cartilage morphology in individuals 2.5 to 4.5 years after ACLR with or without concomitant meniscal pathology and in healthy controls, and (ii) examine the association between baseline patellar cartilage defects and patellar cartilage volume change. METHODS: Thirty two isolated ACLR participants, 25 ACLR participants with combined meniscal pathology and nine healthy controls underwent knee magnetic resonance imaging (MRI) with 2-year intervals (baseline = 2.5 years post-ACLR). Patellar cartilage volume and cartilage defects were assessed from MRI using validated methods. RESULTS: Both ACLR groups showed patellar cartilage volume increased over 2 years (p < 0.05), and isolated ACLR group had greater annual percentage cartilage volume increase compared with controls (mean difference 3.6, 95% confidence interval (CI) 1.0, 6.3%, p = 0.008) and combined ACLR group (mean difference 2.2, 95% CI 0.2, 4.2%, p = 0.028). Patellar cartilage defects regressed in the isolated ACLR group over 2 years (p = 0.02; Z = - 2.33; r = 0.3). Baseline patellar cartilage defect score was positively associated with annual percentage cartilage volume increase (Regression coefficient B = 0.014; 95% CI 0.001, 0.027; p = 0.03) in the pooled ACLR participants. CONCLUSIONS: Hypertrophic response was evident in the patellar cartilage of ACLR participants with and without meniscal pathology. Surprisingly, the increase in patellar cartilage volume was more pronounced in those with isolated ACLR. Although cartilage defects stabilised in the majority of ACLR participants, the severity of patellar cartilage defects at baseline influenced the magnitude of the cartilage hypertrophic response over the subsequent ~ 2 years.

Tibiofemoral joint structural change from 2.5 to 4.5 years following ACL reconstruction with and without combined meniscal pathology.

BACKGROUND: People who have had anterior cruciate ligament reconstruction (ACLR) are at a high risk of developing tibiofemoral joint (TFJ) osteoarthritis (OA), with concomitant meniscal injury elevating this risk. This study aimed to investigate OA-related morphological change over 2 years in the TFJ among individuals who have undergone ACLR with or without concomitant meniscal pathology and in healthy controls. A secondary aim was to examine associations of baseline TFJ cartilage defects and bone marrow lesions (BML) scores with tibial cartilage volume change in ACLR groups. METHODS: Fifty seven ACLR participants aged 18-40 years (32 isolated ACLR, 25 combined meniscal pathology) underwent knee magnetic resonance imaging (MRI) 2.5 and 4.5 years post-surgery. Nine healthy controls underwent knee MRI at the ~ 2-year intervals. Tibial cartilage volume, TFJ cartilage defects and BMLs were assessed from MRI. RESULTS: For both ACLR groups, medial and lateral tibial cartilage volume increased over 2 years (P <  0.05). Isolated ACLR group had greater annual percentage increase in lateral tibial cartilage volume compared with controls and with the combined group (P = 0.03). Cartilage defects remained unchanged across groups. Both ACLR groups showed more lateral tibia BML regression compared with controls (P = 0.04). Baseline cartilage defects score was positively associated with cartilage volume increase at lateral tibia (P = 0.002) while baseline BMLs score was inversely related to medial tibia cartilage volume increase (P = 0.001) in the pooled ACLR group. CONCLUSIONS: Tibial cartilage hypertrophy was apparent in ACLR knees from 2.5 to 4.5 years post-surgery and was partly dependent upon meniscal status together with the nature and location of the underlying pathology at baseline. Magnitude and direction of change in joint pathologies (i.e., cartilage defects, BMLs) were less predictable and either remained stable or improved over follow-up.

Greater knee flexion excursion/moment in hopping is associated with better knee function following anterior cruciate ligament reconstruction.

PURPOSE: Individuals with impaired knee function after anterior cruciate ligament reconstruction (ACLR) may be at greater risk of developing knee osteoarthritis related to abnormal knee joint movement and loading. The aim of this study was to assess the association between knee biomechanics and knee laxity during hopping and clinically assessed knee function (i.e., patient-reported knee function and hop tests) following ACLR. METHODS: Sixty-six participants (23 women, mean age 28 ± 6 years, mean 18 ± 3 months following ACLR) completed a standardized single-leg hopping task. Three-dimensional movement analysis was used to assess knee flexion excursion and body weight/height normalized knee flexion moments during landing for the involved limb. Anterior-posterior knee laxity was assessed with a KT-1000 knee arthrometer. Participants then completed a patient-reported knee function questionnaire and three separate hop tests (% of uninvolved limb) and were divided into poor and satisfactory knee function groups (satisfactory: ≥85% patient-reported knee function and ≥ 85% hop test symmetry). Associations between knee function and hop biomechanics/knee laxity were assessed using logistic regression and interquartile range scaled odds ratios (ORIQR). RESULTS: Greater knee flexion excursion (ORIQR 2.9, 95%CI 1.1-7.8), greater knee flexion moment (ORIQR 4.9, 95%CI 1.6-14.3) and lesser knee laxity (ORIQR 4.7, 95%CI 1.5-14.9) were significantly associated with greater odds of having satisfactory knee function (≥ 85% patient-reported knee function and ≥ 85% hop test symmetry). CONCLUSION: Greater knee flexion excursion/moment during hop-landing and lesser knee laxity is associated with better patient-reported knee function and single-leg hop test performance following ACLR. Patients with lower levels of knee function following ACLR demonstrated hop-landing biomechanics previously associated with early patellofemoral osteoarthritis. Therefore, interventions aimed at improving hop landing biomechanics in people with poor knee function are likely required. LEVEL OF EVIDENCE: III, Cross-sectional study.

Greater magnitude tibiofemoral contact forces are associated with reduced prevalence of osteochondral pathologies 2-3 years following anterior cruciate ligament reconstruction.

PURPOSE: External loading of osteoarthritic and healthy knees correlates with current and future osteochondral tissue state. These relationships have not been examined following anterior cruciate ligament reconstruction. We hypothesised greater magnitude tibiofemoral contact forces were related to increased prevalence of osteochondral pathologies, and these relationships were exacerbated by concomitant meniscal injury. METHODS: This was a cross-sectional study of 100 individuals (29.7 ± 6.5 years, 78.1 ± 14.4 kg) examined 2-3 years following hamstring tendon anterior cruciate ligament reconstruction. Thirty-eight participants had concurrent meniscal pathology (30.6 ± 6.6 years, 83.3 ± 14.3 kg), which included treated and untreated meniscal injury, and 62 participants (29.8 ± 6.4 years, 74.9 ± 13.3 kg) were free of meniscal pathology. Magnetic resonance imaging of reconstructed knees was used to assess prevalence of tibiofemoral osteochondral pathologies (i.e., cartilage defects and bone marrow lesions). A calibrated electromyogram-driven neuromusculoskeletal model was used to predict medial and lateral tibiofemoral compartment contact forces from gait analysis data. Relationships between contact forces and osteochondral pathology prevalence were assessed using logistic regression models. RESULTS: In patients with reconstructed knees free from meniscal pathology, greater medial contact forces were related to reduced prevalence of medial cartilage defects (odds ratio (OR) = 0.7, Wald χ2(2) = 7.9, 95% confidence interval (CI) = 0.50-95, p = 0.02) and medial bone marrow lesions (OR = 0.8, Wald χ2(2) = 4.2, 95% CI = 0.7-0.99, p = 0.04). No significant relationships were found in lateral compartments. In reconstructed knees with concurrent meniscal pathology, no relationships were found between contact forces and osteochondral pathologies. CONCLUSIONS: In patients with reconstructed knees free from meniscal pathology, increased contact forces were associated with fewer cartilage defects and bone marrow lesions in medial, but not, lateral tibiofemoral compartments. No significant relationships were found between contact forces and osteochondral pathologies in reconstructed knees with meniscal pathology for any tibiofemoral compartment. Future studies should focus on determining longitudinal effects of contact forces and changes in osteochondral pathologies. LEVEL OF EVIDENCE: IV.

Poor knee function after ACL reconstruction is associated with attenuated landing force and knee flexion moment during running.

PURPOSE: Poor knee function after anterior cruciate ligament reconstruction (ACLR) may increase the risk of future knee symptoms and knee osteoarthritis via abnormal knee joint loading patterns, particularly during high-impact activity. This study aimed to assess the relationship between poor self-reported or clinically measured knee function and knee moments/vertical ground reaction force (vGRF) in individuals following ACLR. METHODS: 61 participants (mean 16.5 ± 3 months following ACLR, 23 women) completed a patient-reported knee function questionnaire and three hop tests (% of uninvolved limb). Participants were divided into satisfactory and poor knee function groups (poor < 85% patient-reported knee function and/or < 85% hop test symmetry). The knee biomechanics of both groups were assessed with three-dimensional motion analysis during the stance phase of overland running at self-selected speeds, and the association between knee function and knee moments was assessed using analysis of covariance with running speed as a covariate. RESULTS: Participants with poor knee function (n = 30) ran with significantly smaller peak knee flexion moments (moderate effect size 0.7, p = 0.03) and significantly smaller peak vGRFs (large effect size 1.0, p = 0.002) compared to those with satisfactory knee function (n = 31). No significant differences were observed for knee adduction and knee external rotation moments or knee kinematics. CONCLUSION: Individuals following ACLR with poor self-reported knee function and/or hop test performance demonstrate knee moments during running that may be associated with lower knee joint contact forces. These findings provide greater understanding of the relationship between knee biomechanics during running and clinical assessments of knee function. LEVEL OF EVIDENCE: III. Cross-sectional study.

Impaired voluntary quadriceps force control following anterior cruciate ligament reconstruction: relationship with knee function.

PURPOSE: Impairments in quadriceps force control and altered quadriceps and hamstring muscle activation strategies have been observed following anterior cruciate ligament reconstruction; however, the functional implications of these impairments are unclear. This study examined the cross-sectional associations between quadriceps force control, quadriceps activation, hamstring coactivation and clinically assessed knee function following anterior cruciate ligament reconstruction with a hamstring graft. METHODS: Sixty-six patients (18 ± 3 months following surgery) and 41 uninjured individuals participated. Quadriceps force control was assessed using an isometric knee extension task. Participants cyclically increased and decreased quadriceps force at slow speeds between 5 and 30 % maximum voluntary isometric contraction matching a moving target displayed on a screen. Quadriceps activation and hamstring coactivation were assessed concurrently using surface electromyography. Knee function was assessed with the Cincinnati Knee Rating Scale and three single-leg hop tests. RESULTS: The reconstructed group completed the task with 48 % greater root-mean-square error (RMSE), indicating significantly worse quadriceps force control (p < 0.001). In a multivariable model adjusted for sex, greater RMSE and greater lateral hamstring coactivation were significantly associated with worse knee function that is greater odds of scoring <85 % on one or more knee functional assessment. CONCLUSIONS: Less-accurate quadriceps force output and greater hamstring coactivation are associated with worse knee joint function following anterior cruciate ligament reconstruction and may contribute to irregular knee joint loading and the onset or progression of knee osteoarthritis. Impairments in quadriceps force control and altered muscle activation strategies may be modifiable through neuromuscular training, and this is an area for future research. LEVEL OF EVIDENCE: Case-control study, Level III.

Cartilage morphology at 2-3 years following anterior cruciate ligament reconstruction with or without concomitant meniscal pathology.

PURPOSE: To examine differences in cartilage morphology between young adults 2-3 years post-anterior cruciate ligament reconstruction (ACLR), with or without meniscal pathology, and control participants. METHODS: Knee MRI was performed on 130 participants aged 18-40 years (62 with isolated ACLR, 38 with combined ACLR and meniscal pathology, and 30 healthy controls). Cartilage defects, cartilage volume and bone marrow lesions (BMLs) were assessed from MRI using validated methods. RESULTS: Cartilage defects were more prevalent in the isolated ACLR (69 %) and combined group (84 %) than in controls (10 %, P < 0.001). Furthermore, the combined group showed higher prevalence of cartilage defects on medial femoral condyle (OR 4.7, 95 % CI 1.3-16.6) and patella (OR 7.8, 95 % CI 1.5-40.7) than the isolated ACLR group. Cartilage volume was lower in both ACLR groups compared with controls (medial tibia, lateral tibia and patella, P < 0.05), whilst prevalence of BMLs was higher on lateral tibia (P < 0.001), with no significant differences between the two ACLR groups for either measure. CONCLUSIONS: Cartilage morphology was worse in ACLR patients compared with healthy controls. ACLR patients with associated meniscal pathology have a higher prevalence of cartilage defects than ACLR patients without meniscal pathology. The findings suggest that concomitant meniscal pathology may lead to a greater risk of future OA than isolated ACLR. LEVEL OF EVIDENCE: III.

Does meniscal pathology alter gait knee biomechanics and strength post-ACL reconstruction?

PURPOSE: Individuals following anterior cruciate ligament reconstruction (ACLR) with concomitant meniscal pathology have a higher risk of developing knee osteoarthritis (OA) compared to those with isolated ACLR. Knee extensor weakness and altered dynamic knee joint biomechanics have been suggested to play a role in the development of knee OA following ACLR. This study investigated whether these factors differ in people following ACLR who have concomitant meniscal pathology compared to patients with isolated ACLR. METHODS: Thirty-three patients with isolated ACLR and 34 patients with ACLR and meniscal pathology underwent strength and gait assessment 12-24 months post-operatively. Primary measures were peak isometric knee extensor torque and knee adduction moment (peak and impulse). Secondary measures included peak knee flexion moment and knee kinematics (sagittal and transverse). RESULTS: There were no between-group differences in knee extensor strength [mean difference (95 % CI) 0.09 (-0.23 to 0.42) Nm/kg, n.s.], peak knee adduction moment [-0.02 (-0.54 to 0.49) Nm/(BW × HT) %, n.s.] or knee adduction moment impulse [0.01 (-0.15 to 0.17) Nm/(BW × HT) %, p = n.s.]. No between-group differences were found for any secondary measures. CONCLUSIONS: No evidence was found to suggest that the higher prevalence of OA in patients with ACLR and meniscal pathology compared to patients with isolated ACLR is attributed to reduced knee muscle strength or altered knee joint biomechanics assessed 1-2 years post-surgery. Given that there is a higher incidence of knee OA in patients with concomitant meniscal pathology and ACLR, further investigation is needed so that population-specific rehabilitation protocols can be developed. LEVEL OF EVIDENCE: III.

Clinic-based assessment of weight-bearing asymmetry during squatting in people with anterior cruciate ligament reconstruction using Nintendo Wii Balance Boards.

OBJECTIVE: To use low-cost Nintendo Wii Balance Boards (NWBB) to assess weight-bearing asymmetry (WBA) in people who have undergone anterior cruciate ligament reconstruction (ACLR), and to compare their results with a matched control group. DESIGN: Quantitative clinical study using a cross-sectional design. SETTING: Orthopedic clinic of a private hospital. PARTICIPANTS: ACLR participants (n=41; mean age ± SD, 26.0 ± 9.8 y; current Cincinnati sports activity level, 75.3 ± 19.8) performed testing in conjunction with their routine 6- or 12-month clinical follow-up, and a control group (n=41) was matched for age, height, body mass, and physical activity level. INTERVENTIONS: Participants performed double-limb squats while standing on 2 NWBBs, 1 under each foot. MAIN OUTCOME MEASURES: The WBA variables mean mass difference as a percentage of body mass, time favoring a single limb by >5% body mass, absolute symmetry index, and symmetry index relative to the operated or matched control limb were derived. Mann-Whitney U tests were performed to assess between-group differences. RESULTS: Significant (P<.05) increases in asymmetry in the ACLR group were found for all outcome measures except symmetry index relative to the operated limb. CONCLUSIONS: People who have undergone ACLR are likely to possess WBA during squats, and this can be assessed using low-cost NWBBs in a clinical setting. Interestingly, the observed asymmetry was not specific to the surgical limb. Future research is needed to assess the relationship between WBA early in the rehabilitation process and long-term outcomes.

Hip rotation muscle strength is implicated in the progression of early post-traumatic osteoarthritis: A longitudinal evaluation up to 5 years following ACL reconstruction.

INTRODUCTION: Following ACL reconstruction (ACLR), deficits in hip muscle strength and relationships to future outcomes are unknown. METHODS: 111 participants one year after ACLR, completed hip external rotation (ER) and internal rotation (IR) strength assessment. At 1 (n = 111) and 5 (n = 74) years post-ACLR, participants completed a battery of functional, symptomatic (Knee Osteoarthritis Outcome Score (KOOS)) and structural assessments (radiography, magnetic resonance imaging (MRI)). Cartilage health of the patellofemoral and tibiofemoral compartments was assessed with the semiquantitative MRI Osteoarthritis Knee Score. Hip rotation strength was compared between-limbs, and relationships between hip strength at 1 year and functional, symptomatic and cartilage outcomes at 1 and 5 years were investigated with regression models. RESULTS: The index (ACLR) limb had weaker hip ER (but not IR) strength compared to the contralateral side (standardised mean difference ER = -0.33 (95%CI -0.60, -0.07; IR = -0.11 (95%CI -0.37, 0.15). Greater hip ER and IR strength was associated with superior function at 1 and 5 years, and better KOOS-Patellofemoral symptoms at 5 years. Greater hip ER strength was associated with lower odds of worsening tibiofemoral cartilage lesions at 5 years (odds ratio 0.01, 95%CI 0.00, 0.41). CONCLUSION: Hip rotation strength may play a role in worsening function, symptoms and cartilage health after ACLR.

Rosetta in CAPRI rounds 13-19.

Modeling the conformational changes that occur on binding of macromolecules is an unsolved challenge. In previous rounds of the Critical Assessment of PRediction of Interactions (CAPRI), it was demonstrated that the Rosetta approach to macromolecular modeling could capture side chain conformational changes on binding with high accuracy. In rounds 13-19 we tested the ability of various backbone remodeling strategies to capture the main-chain conformational changes observed during binding events. These approaches span a wide range of backbone motions, from limited refinement of loops to relieve clashes in homologous docking, through extensive remodeling of loop segments, to large-scale remodeling of RNA. Although the results are encouraging, major improvements in sampling and energy evaluation are clearly required for consistent high accuracy modeling. Analysis of our failures in the CAPRI challenges suggest that conformational sampling at the termini of exposed beta strands is a particularly pressing area for improvement.

Does patellar alignment or trochlear morphology predict worsening of patellofemoral disease within the first 5 years after anterior cruciate ligament reconstruction?

PURPOSE: We described patellofemoral alignment and trochlear morphology at one and five years after anterior cruciate ligament reconstruction (ACLR), and evaluated the associations between alignment and trochlear morphology (at one year) and worsening patellofemoral osteoarthritis (OA) features by five years. We also evaluated the associations between alignment and morphology to self-reported pain and function (Knee injury and Osteoarthritis Outcome Score, KOOS) at five years. MATERIALS AND METHODS: In this longitudinal observational study, we followed 73 participants (mean age 29[9] years, 40% women) from one- to five-years after ACLR. Using MRI, we measured alignment and morphology, and scored cartilage and bone marrow lesions at both time points. We used mixed effects and linear regression models to achieve our stated aims. RESULTS: Greater lateral patella displacement increased risk of cartilage worsening (Odds Ratio [95% CI]: 1.09 [1.01, 1.16]); while less lateral tilt (0.91 [0.83, 0.99]) and greater trochlear angle (0.88 [0.77, 1.00]) were protective. Greater medial trochlear inclination increased risk of bone marrow lesion worsening (1.12 [1.04, 1.19]); while greater trochlear angle was protective (0.80 [0.67, 0.96]). Greater lateral displacement was associated with worse self-reported KOOS sport and recreation scores (ß [95% CI]: -11.0 [-20.9, -1.2]) and quality of life scores (-10.5 [-20.4, -0.7]). CONCLUSIONS: Lateral displacement, lateral tilt, and morphology at 1 year post-ACLR altered the risk of worsening patellofemoral OA features four years later. Lateral displacement was the only measure associated with worse self-reported symptoms at five years. These findings may lead to novel treatment strategies for secondary prevention after ACLR.

Surgical treatments of cartilage defects of the knee: Systematic review of randomised controlled trials.

BACKGROUND: The aim of this systematic review was to identify high quality randomised controlled trials (RCTs) and to provide an update on the most appropriate surgical treatments for knee cartilage defects. METHODS: Two reviewers independently searched three databases for RCTs comparing at least two different treatment techniques for knee cartilage defects. The search strategy used terms mapped to relevant subject headings of MeSH terms. Strict inclusion and exclusion criteria were used to identify studies with patients aged between 18 and 55 years with articular cartilage defects sized between one and 15cm2. Risk of bias was performed using a Coleman Methodology Score. Data extracted included patient demographics, defect characteristics, clinical outcomes, and failure rates. RESULTS: Ten articles were included (861 patients). Eight studies compared microfracture to other treatment; four to autologous chondrocyte implantation (ACI) or matrix-induced ACI (MACI); three to osteochondral autologous transplantation (OAT); and one to BST-Cargel. Two studies reported better results with OAT than with microfracture and one reported similar results. Two studies reported superior results with cartilage regenerative techniques than with microfracture, and two reported similar results. At 10years significantly more failures occurred with microfracture compared to OAT and with OAT compared to ACI. Larger lesions (>4.5cm2) treated with cartilage regenerative techniques (ACI/MACI) had better outcomes than with microfracture. CONCLUSIONS: Based on the evidence from this systematic review no single treatment can be recommended for the treatment of knee cartilage defects. This highlights the need for further RCTs, preferably patient-blinded, using an appropriate reference treatment or a placebo procedure.

Relationships Between Tibiofemoral Contact Forces and Cartilage Morphology at 2 to 3 Years After Single-Bundle Hamstring Anterior Cruciate Ligament Reconstruction and in Healthy Knees.

BACKGROUND: Prevention of knee osteoarthritis (OA) following anterior cruciate ligament (ACL) rupture and reconstruction is vital. Risk of postreconstruction knee OA is markedly increased by concurrent meniscal injury. It is unclear whether reconstruction results in normal relationships between tibiofemoral contact forces and cartilage morphology and whether meniscal injury modulates these relationships. HYPOTHESES: Since patients with isolated reconstructions (ie, without meniscal injury) are at lower risk for knee OA, we predicted that relationships between tibiofemoral contact forces and cartilage morphology would be similar to those of normal, healthy knees 2 to 3 years postreconstruction. In knees with meniscal injuries, these relationships would be similar to those reported in patients with knee OA, reflecting early degenerative changes. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Three groups were examined: (1) 62 patients who received single-bundle hamstring reconstruction with an intact, uninjured meniscus (mean age, 29.8 ± 6.4 years; mean weight, 74.9 ± 13.3 kg); (2) 38 patients with similar reconstruction with additional meniscal injury (ie, tear, repair) or partial resection (mean age, 30.6 ± 6.6 years; mean weight, 83.3 ± 14.3 kg); and (3) 30 ligament-normal, healthy individuals (mean age, 28.3 ± 5.2 years; mean weight, 74.9 ± 14.9 kg) serving as controls. All patients underwent magnetic resonance imaging to measure the medial and lateral tibial articular cartilage morphology (volumes and thicknesses). An electromyography-driven neuromusculoskeletal model determined medial and lateral tibiofemoral contact forces during walking. General linear models were used to assess relationships between tibiofemoral contact forces and cartilage morphology. RESULTS: In control knees, cartilage was thicker compared with that of isolated and meniscal-injured ACL-reconstructed knees, while greater contact forces were related to both greater tibial cartilage volumes (medial: R2 = 0.43, ß = 0.62, P = .000; lateral: R2 = 0.19, ß = 0.46, P = .03) and medial thicknesses (R2 = 0.24, ß = 0.48, P = .01). In the overall group of ACL-reconstructed knees, greater contact forces were related to greater lateral cartilage volumes (R2 = 0.08, ß = 0.28, P = .01). In ACL-reconstructed knees with lateral meniscal injury, greater lateral contact forces were related to greater lateral cartilage volumes (R2 = 0.41, ß = 0.64, P = .001) and thicknesses (R2 = 0.20, ß = 0.46, P = .04). CONCLUSION: At 2 to 3 years postsurgery, ACL-reconstructed knees had thinner cartilage compared with healthy knees, and there were no positive relationships between medial contact forces and cartilage morphology. In lateral meniscal-injured reconstructed knees, greater contact forces were related to greater lateral cartilage volumes and thicknesses, although it was unclear whether this was an adaptive response or associated with degeneration. Future clinical studies may seek to establish whether cartilage morphology can be modified through rehabilitation programs targeting contact forces directly in addition to the current rehabilitation foci of restoring passive and dynamic knee range of motion, knee strength, and functional performance.

Tibiofemoral Contact Forces in the Anterior Cruciate Ligament-Reconstructed Knee.

PURPOSE: To investigate differences in anterior cruciate ligament-reconstructed (ACLR) and healthy individuals in terms of the magnitude of the tibiofemoral contact forces, as well as the relative muscle and external load contributions to those contact forces, during walking, running, and sidestepping gait tasks. METHODS: A computational EMG-driven neuromusculoskeletal model was used to estimate the muscle and tibiofemoral contact forces in those with single-bundle combined semitendinosus and gracilis tendon autograft ACLR (n = 104, 29.7 ± 6.5 yr, 78.1 ± 14.4 kg) and healthy controls (n = 60, 27.5 ± 5.4 yr, 67.8 ± 14.0 kg) during walking (1.4 ± 0.2 m·s), running (4.5 ± 0.5 m·s) and sidestepping (3.7 ± 0.6 m·s). Within the computational model, the semitendinosus of ACLR participants was adjusted to account for literature reported strength deficits and morphological changes subsequent to autograft harvesting. RESULTS: ACLR had smaller maximum total and medial tibiofemoral contact forces (~80% of control values, scaled to bodyweight) during the different gait tasks. Compared with controls, ACLR were found to have a smaller maximum knee flexion moment, which explained the smaller tibiofemoral contact forces. Similarly, compared with controls, ACLR had both a smaller maximum knee flexion angle and knee flexion excursion during running and sidestepping, which may have concentrated the articular contact forces to smaller areas within the tibiofemoral joint. Mean relative muscle and external load contributions to the tibiofemoral contact forces were not significantly different between ACLR and controls. CONCLUSIONS: ACLR had lower bodyweight-scaled tibiofemoral contact forces during walking, running, and sidestepping, likely due to lower knee flexion moments and straighter knee during the different gait tasks. The relative contributions of muscles and external loads to the contact forces were equivalent between groups.

Assessment of standing balance deficits in people who have undergone anterior cruciate ligament reconstruction using traditional and modern analysis methods.

Modern methods of assessing standing balance such as wavelet and entropy analysis could provide insight into postural control mechanisms in clinical populations. The aim of this study was to examine what effect anterior cruciate ligament reconstruction (ACLR) has on traditional and modern measures of balance. Ninety subjects, 45 who had undergone ACLR and 45 matched controls, performed single leg static standing balance tests on their surgical or matched limb on a Nintendo Wii Balance Board. Data were analysed in the anterior-posterior axis of movement, which is known to be affected by ACLR. The traditional measures of path velocity, amplitude and standard deviation were calculated in this plane. Additionally, sample entropy and discrete wavelet transform derived assessment of path velocity in four distinct frequency bands related to (1) spinal reflexive loops and muscle activity, (2) cerebellar, (3) vestibular, and (4) visual mechanisms of postural control were derived. The ACLR group had significantly increased values in all traditional measures and all four frequency bands. No significant difference was observed for sample entropy. This indicated that whilst postural sway was amplified in the ACLR group, the overall mechanism used by the patient group to maintain balance was similar to that of the control group. In conclusion, modern methods of signal analysis may provide additional insight into standing balance mechanisms in clinical populations. Future research is required to determine if these results provide important and unique information which is of benefit to clinicians.

The effect of urban quality improvements on economic activity.

This paper is concerned with the link between urban quality improvements and economic activity. A key question is whether improvements in the urban environment which might be achieved, for instance, through pedestrianisation, will affect business location choices--for example, are office or retail businesses particularly keen to locate in more pleasant urban places? The paper outlines the current state of development of the literature with respect to the influence of urban quality on economic activity, and proposes a framework for forecasting economic impacts based on three communities of reference: customers, employees, and the businesses themselves. The results from original modelling of a case study area in Manchester, England are reported and suggest that the positive uplifts that may be expected from environmental improvement programmes may well be on a scale which is significant. The research is obviously important for the urban regeneration and renaissance agendas which posit attractive and well-designed environments as a way to create the right conditions for promoting economic growth.