High tibial osteotomy to neutral alignment improves medial knee articular cartilage composition.

PURPOSE: The purpose of this study was to: (1) test the hypothesis that HTO improves articular cartilage composition in the medial compartment without adversely affecting the lateral compartment and patella, and; (2) explore associations between knee alignment and cartilage composition after surgery. METHODS: 3T MRI and standing radiographs were obtained from 34 patients before and 1-year after HTO. Articular cartilage was segmented from T2 maps. Mechanical axis angle (MAA), posterior tibial slope, and patellar height were measured from radiographs. Changes in T2 and radiographic measures were assessed using paired t tests, and associations were assessed using Pearson correlation coefficients. RESULTS: The mean (SD) MAA before and after HTO was - 6.5° (2.4) and 0.6° (3.0), respectively. There was statistically significant shortening [mean (95%CI)] of T2 in the medial femur [- 2.8 ms (- 4.2; - 1.3), p < 0.001] and medial tibia [- 2.2 ms (- 3.3; - 1.0), p < 0.001], without changes in the lateral femur [- 0.5 ms (- 1.6; 0.6), p = 0.3], lateral tibia [0.2 ms (- 0.8; 1.1), p = NS], or patella [0.5 ms (- 1.0; 2.1), p = NS). Associations between radiographic measures and T2 were low. 23% of the increase in lateral femur T2 was explained by postoperative posterior tibial slope (r = 0.48). CONCLUSION: Performing medial opening wedge HTO without overcorrection improves articular cartilage composition in the medial compartment of the knee without compromising the lateral compartment or the patella. Although further research is required, these results suggest HTO is a disease structure-modifying treatment for knee OA.

Synovial tissue perivascular edema is associated with altered gait patterns in patients with knee osteoarthritis.

OBJECTIVE: To explore mechanisms of mechanoinflammation, we investigated the association between the presence of knee synovial perivascular edema and gait biomechanics that serve as surrogate measures of knee load in patients with knee osteoarthritis (OA). DESIGN: Patients with symptomatic, radiographic knee OA and neutral to varus alignment undergoing total knee arthroplasty or high tibial osteotomy participated in this cross-sectional analysis. All participants underwent 3D gait analysis prior to surgery. Synovial biopsies were obtained during surgery for histopathological assessment. The association between the presence of synovial perivascular edema (predictor) and the external knee moment (outcome) in each orthogonal plane was analyzed using multivariate linear regression and polynomial mixed effects regression models, while adjusting for age, sex, BMI, and gait speed. RESULTS: Ninety-two patients with complete gait and histopathological data were included. When fitted over 100% of stance, regression models indicated substantial differences between patients with and without synovial perivascular edema for knee moments in frontal, sagittal and transverse planes. The knee adduction moment was higher in patients with edema from 16 to 74% of stance, with the largest difference at 33% of stance (ß = 6.87 Nm [95%CI 3.02, 10.72]); whereas the knee flexion-extension moment differed from 15 to 92% of stance, with the largest difference in extension at 60% of stance (ß = -10.80 Nm [95%CI -16.20, -5.40]). CONCLUSIONS: In patients with knee OA, the presence of synovial perivascular edema identified by histopathology is associated with aberrant patterns of knee loading throughout stance, supporting the link between biomechanics and synovial inflammation.

Association between changes in knee load and effusion-synovitis: evidence of mechano-inflammation in knee osteoarthritis using high tibial osteotomy as a model.

OBJECTIVE: Although mechanically-induced inflammation is an appealing explanation linking different etiologic factors in osteoarthritis (OA), clinical research investigating changes in both biomechanics and joint inflammation is limited. The purpose of this study was to evaluate the association between change in surrogate measures of knee load and knee effusion-synovitis in patients with medial compartment knee OA undergoing high tibial osteotomy (HTO). METHODS: Thirty-six patients with medial compartment knee OA and varus alignment underwent 3D gait analysis and 3T magnetic resonance imaging (MRI) preoperatively and 1 year after medial opening wedge HTO. Primary outcome measures were the change in the external knee adduction moment impulse during walking and change in knee suprapatellar effusion-synovitis volume manually segmented on MRI by one blinded assessor. RESULTS: Mean (SD) knee adduction moment impulse [24.0 (6.5) Nm•s] and knee effusion-synovitis volume [8976.7 (8016.9) mm3] suggested substantial preoperative medial knee load and inflammation. 1-year postoperative changes in knee adduction moment impulse [-10.1 Nm•s (95%CI: -12.7, -7.4)], and knee effusion-synovitis volume [-1856 mm3 (95%CI: -3830, 117)] were positively correlated [r = 0.60 (95% CI 0.34, 0.78)]. Simple linear regression suggested a 448 mm3 (95%CI: 241, 656) reduction in knee effusion-synovitis volume per 1 Nm•s reduction in knee adduction moment impulse. Change in knee adduction moment impulse explained 36% (R2 = 0.36) of the variance of change in knee effusion-synovitis volume. CONCLUSIONS: Reduction in medial knee load is positively associated with reduction in knee inflammation after HTO, suggesting the phenomenon of mechano-inflammation in patients with knee OA.

Trajectories of perceived exertion and pain over a 12-week neuromuscular exercise program in patients with knee osteoarthritis.

BACKGROUND: Exercise programs rely on the overload principle, yet patients with knee osteoarthritis (OA) may not adequately progress exercises due to fear of exacerbating symptoms. OBJECTIVE: To describe trajectories for perceived exertion and exercise-induced knee pain during a neuromuscular exercise program for patients with knee OA. DESIGN: Participants with knee OA completed a 12-week neuromuscular exercise program consisting of weekly supervised sessions plus home exercises. During each supervised session, the Borg's rating of perceived exertion (RPE; 6 = no exertion, 20 = maximal exertion) and knee pain (pre, post, max) using Numeric Rating Scales (NRS; 0 = no pain, 10 = worst imaginable pain) were completed. Mean changes in RPE and pain from weeks 1-12 were calculated. Mixed effects regression was used to investigate trajectories over time (weeks) for RPE, and maximum pain (pre-to-max) and pain-change (pre-to-post) during exercise. RESULTS: 56 patients (95%) completed the program. From week 1-12, RPE increased by 2.6 (95%CI, 1.7 to 3.5), from 'somewhat hard' to 'very hard', while max pain decreased by 1.0 NRS (95%CI, 0.5 to 1.3) and pain-change decreased by 0.9 NRS (95%CI, 0.4 to 1.3). Linear mixed effects regression showed a quadratic increase for RPE over time until between weeks 9 and 10, then RPE plateaued. Maximum pain decreased linearly over time. Pain-change showed a quadratic decrease over time until approximately week 9, then pain-change plateaued. CONCLUSIONS: In patients with knee OA participating in a 12-week neuromuscular exercise program, perceived exertion during exercise progressed from 'somewhat hard' to 'very hard' at 9 weeks, while exercise-induced knee pain decreased. Patients were able to work harder while experiencing decreases rather than increases in pain.

The star excursion balance test is a reliable and valid outcome measure for patients with knee osteoarthritis.

OBJECTIVES: Despite the recognized importance of neuromuscular exercises, there is currently no widely accepted clinical outcome measure focused on neuromuscular control for patients with knee osteoarthritis (OA). The purposes of the present study were to investigate the test-retest reliability, concurrent validity and longitudinal validity of the star excursion balance test (SEBT) in patients with knee OA. DESIGN: 74 patients performed the SEBT on two sessions within 7 days, and on a third session after completing 12 weeks of a home exercise program focused on neuromuscular control. A subgroup of 37 performed the SEBT while in the field of view of a motion capture system to estimate concurrent validity. The SEBT was recorded in cm and also normalized to leg length (LL). Participants also completed the 40 m fast-paced walk test and patient-reported outcomes before and after the exercise program. RESULTS: Intraclass correlation coefficients (95% confidence intervals) were 0.94 (0.91 to 0.96) and 0.93 (0.89 to 0.96) and standard errors of measurement were ±2.68 cm and ±3.05%LL for raw and normalized composite scores, respectively. The minimum detectable change at the 95% confidence level for the composite score was 7.44 cm and 8.45%LL. Correlations between observer and motion capture measures were very high (Pearson r > 0.96). There was a significant increase in SEBT following the exercise program (standardized response mean = 0.74). The change in SEBT had low correlations with changes in 40 m walk times (r = 0.26) and pain (r = 0.28). CONCLUSION: The SEBT has suitable measurement properties for use in patients with knee OA.

Changes in biomechanical risk factors for knee osteoarthritis and their association with 5-year clinically important improvement after limb realignment surgery.

OBJECTIVE: To evaluate 5-year outcomes after lower limb realignment and test the hypothesis that surgery-induced changes in selected biomechanical risk factors for medial knee osteoarthritis (OA) are associated with clinically important improvements. DESIGN: We prospectively evaluated patient-reported outcomes, full-limb standing radiographs and gait biomechanics before, 6 months (surgery-induced change) and 5 years after medial opening wedge high tibial osteotomy (HTO) in 170 patients (46.4 ± 8.9 years, 135 males) with knee OA and varus alignment. Logistic regression tested the associations of 6-month changes in mechanical axis angle and knee adduction moment with achieving an increase of ≥10 points in the Knee injury and Osteoarthritis Outcome Score (KOOS)4 at 5 years, with and without adjusting for covariates. Gait data were also compared to existing data from healthy controls. RESULTS: Mean 5-year changes (95% confidence interval (CI)) were: KOOS4: +14.2 (10.8, 17.6); mechanical axis angle: +8.21° (7.58, 8.83); knee adduction moment: -1.49 %BW*Ht (-1.35, -1.63). The postoperative knee adduction moments were typically lower than values for healthy controls. When divided into quartiles, although all strata improved significantly, patients with reductions in knee adduction moment of 1.14-1.74 %BW*Ht (neither largest nor smallest changes) had highest 5-year KOOS4 scores. The 6-month change in knee adduction moment (odds ratios (OR) = 0.38; 95% CI: 0.22, 0.67), preoperative KOOS4 (OR = 0.96; 95% CI: 0.94, 0.99) and preoperative medial tibiofemoral narrowing grade (OR = 0.62; 95% CI: 0.37, 1.00) were negatively associated with having a 5-year clinically important improvement (C-statistic = 0.70). CONCLUSIONS: Substantial improvements in biomechanical risk factors and patient-reported outcomes are observed 5 years after medial opening wedge HTO. The surgery-induced change in load distribution during walking is significantly associated with long-term clinically important improvement.

Biomechanical effects of valgus knee bracing: a systematic review and meta-analysis.

To review and synthesize the biomechanical effects of valgus knee bracing for patients with medial knee osteoarthritis (OA). Electronic databases were searched from their inception to May 2014. Two reviewers independently determined study eligibility, rated study quality and extracted data. Where possible, data were combined into meta-analyses and pooled estimates with 95% confidence intervals (CI) for standardized mean differences (SMD) were calculated. Thirty studies were included with 478 subjects tested while using a valgus knee brace. Various biomechanical methods suggested valgus braces can decrease direct measures of medial knee compressive force, indirect measures representing the mediolateral distribution of load across the knee, quadriceps/hamstring and quadriceps/gastrocnemius co-contraction ratios, and increase medial joint space during gait. Meta-analysis from 17 studies suggested a statistically significant decrease in the external knee adduction moment (KAM) during walking, with a moderate-to-high effect size (SMD = 0.61; 95% CI: 0.39, 0.83; P < 0.001). Meta-regression identified a near-significant association for the KAM effect size and duration of brace use only (ß, -0.01; 95% CI: -0.03, 0.0001; P = 0.06); with longer durations of brace use associated with smaller treatment effects. Minor complications were commonly reported during brace use and included slipping, discomfort and poor fit, blisters and skin irritation. Systematic review and meta-analysis suggests valgus knee braces can alter knee joint loads through a combination of mechanisms, with moderate-to-high effect sizes in biomechanical outcomes.

High tibial osteotomy: evolution of research and clinical applications--a Canadian experience.

PURPOSE: This narrative review describes experiences at the Fowler Kennedy Sport Medicine Clinic (FKSMC) with high tibial osteotomy (HTO) for patients with varus gonarthrosis, with particular focus on research published from the unit that has guided practice. METHODS: The goals of surgery are to improve alignment of the weight bearing axis of the lower limb to lessen the load on the medial tibiofemoral compartment and thereby decrease these important risk factors for disease progression. The overall aims are to improve knee function and delay or even prevent the eventual need for arthroplasty. To achieve these aims, a medial opening wedge osteotomy is utilised, deliberately avoiding an over correction of the lower limb, but tailoring the angle of correction to an individual patient's characteristics. With such an approach, patients with a broad range of characteristics (including age, BMI and lateral compartment involvement) can benefit from the procedure. In addition, the HTO can be used with concomitant procedures to address specific presentations, such as large deformities and instability. RESULTS: The results suggest that correction to a slight valgus alignment produces approximately 50% reduction in medial compartment loads during gait with large, clinically important improvements in patient-reported outcomes at 2-years postoperatively. In patients with substantial bilateral varus deformity, unilateral surgery can lead to increased dynamic knee joint loads on the nonoperative limb after surgery. This means that such patients require the close monitoring of both limbs and consideration of a staged, bilateral procedure if necessary. In patients requiring bilateral surgery, similar results after bilateral HTO to those after unilateral surgery have been reported. For patients requiring large corrections, the need for a concomitant tibial tubercle osteotomy to reduce the potential for iatrogenic patella infera is considered. Finally, HTO procedures can also be used in patients with instability, either to alter both sagittal and coronal alignment to correct instability in complex ligament deficiencies or to undertake simultaneous HTO and ACL reconstruction. CONCLUSIONS: HTO is being used both alone and in conjunction with concomitant procedures with good clinical results. While continued investigation into patient selection and outcomes are required, current research indicates that HTO offers at least a partial solution for the patient with varus gonarthrosis to prolong the life of their native knee joint. LEVEL OF EVIDENCE: V.

The effect of walking poles on the knee adduction moment in patients with varus gonarthrosis.

OBJECTIVES: (1) Test the hypothesis that walking poles decrease the external knee adduction moment during gait in patients with varus gonarthrosis, and (2) explore potential mechanisms. DESIGN: Thirty-four patients with medial compartment knee osteoarthritis (OA) and varus alignment underwent three dimensional (3D) gait analysis with and without using walking poles. Conditions were randomized and walking speed was maintained ±5% of the self-selected speed of the initial condition. The pole held in the hand of the unaffected side was instrumented with a compression load cell. RESULTS: Student's t tests for paired samples indicated small but statistically significant increases (P < 0.001) in knee adduction moment (calculated from inverse dynamics) for its first peak, second peak and angular impulse when using the poles; mean increases (95% confidence interval - CI) were 0.17%BW*Ht (0.08, 0.27), 0.17%BW*Ht (0.04, 0.30) and 0.15%BW*Ht*s (0.09, 0.22), respectively. There was a decrease (P = 0.015) in vertical ground reaction force (-0.02 BW (-0.04, -0.01)), yet increase (P < 0.001) in its frontal plane lever arm about the knee (0.30 cm (0.15, 0.44)), at the time of the first peak knee adduction moment. Pole force in the vertical direction was inversely related (r = -0.34, P = 0.05) to the increase in first peak adduction moment. CONCLUSION: Although results are variable among patients, and may be related to individual technique, these overall findings suggest that walking poles do not decrease knee adduction moments, and therefore likely do not decrease medial compartment loads, in patients with varus gonarthrosis. Decreases in knee joint loading should not be used as rationale for walking pole use in these patients.

Alignment, body mass and their interaction on dynamic knee joint load in patients with knee osteoarthritis.

OBJECTIVE: To examine the interaction and relative contributions of frontal plane alignment and body mass on dynamic knee joint loading in patients with knee osteoarthritis (OA). METHODS: We completed three-dimensional gait analyses and hip-to-ankle standing anteroposterior radiographs on 487 patients with knee OA referred to a tertiary care center specializing in orthopaedics. RESULTS: Using sequential (hierarchical) linear regression, the interaction term (mechanical axis anglexmass) contributed significantly (P<0.001) to a model (total adjusted R(2)=0.70) predicting the external knee adduction moment, that included mechanical axis angle (R(2)=0.37) and mass (R(2)=0.06) while controlling for age, sex, height, Kellgren and Lawrence grade, pain score during walking, gait speed, toe out angle and trunk lean (R(2)=0.25). When the sample was split into tertiles for mass, mechanical axis angle accounted for 32-54% of explained variance in knee adduction moment. In the tertile with greatest mass, results suggest a 3.2 N m increase in knee load for every 1 degrees increase in varus alignment. When split into tertiles for mechanical axis angle, mass accounted for 6-10% of explained variance in the knee adduction moment. In the tertile with the most varus alignment, results suggest a 0.4 N m increase in knee load for every 1 kg increase in mass. CONCLUSION: Our findings describe the interaction between alignment and body mass on dynamic knee joint loading, with the association between alignment and load highest in patients with the highest mass. Our findings also emphasize the role of malalignment on knee load at all levels of mass, and have implications for better understanding risk factors and intervention strategies for knee OA.

A comparison of subtalar joint motion during anticipated medial cutting turns and level walking using a multi-segment foot model.

The weight-bearing in-vivo kinematics and kinetics of the talocrural joint, subtalar joint and joints of the foot were quantified using optical motion analysis. Twelve healthy subjects were studied during level walking and anticipated medial turns at self-selected pace. A multi-segment model of the foot using skin-mounted marker triads tracked four foot segments: the hindfoot, midfoot, lateral and medial forefoot. The lower leg and thigh were also tracked. Motion between each of the segments could occur in three degrees of rotational freedom, but only six inter-segmental motions were reported in this study: (1) talocrural dorsi-plantar-flexion, (2) subtalar inversion-eversion, (3) frontal plane hindfoot motion, (4) transverse plane hindfoot motion, (5) forefoot supination-pronation twisting and (6) the height-to-length ratio of the medial longitudinal arch. The motion at the subtalar joint during stance phase of walking (eversion then inversion) was reversed during a turning task (inversion then eversion). The external subtalar joint moment was also changed from a moderate eversion moment during walking to a larger inversion moment during the turn. The kinematics of the talocrural joint and the joints of the foot were similar between these two tasks. During a medial turn, the subtalar joint may act to maintain the motions in the foot and talocrural joint that occur during level walking. This is occurring despite the conspicuously different trajectory of the centre of mass of the body. This may allow the foot complex to maintain its function of energy absorption followed by energy return during stance phase that is best suited to level walking.

Lateral trunk lean explains variation in dynamic knee joint load in patients with medial compartment knee osteoarthritis.

OBJECTIVE: To test the hypothesis that selected gait kinematics, particularly lateral trunk lean, observed in patients with medial compartment knee osteoarthritis explain variation in dynamic knee joint load. METHOD: In this cross-sectional observational study, 120 patients with radiographically confirmed varus gonarthrosis underwent three-dimensional gait analysis at their typical walking speed. We used sequential (hierarchical) linear regression to examine the amount of variance in dynamic knee joint load (external knee adduction moment) explained by static lower limb alignment (mechanical axis angle) and gait kinematics determined a priori based on their proposed effect on knee load (walking speed, toe-out angle, and lateral trunk lean angle). RESULTS: Approximately 50% of the variation in the first peak external knee adduction moment was explained by mechanical axis angle (25%), Western Ontario and McMaster Universities Osteoarthritis Index pain score (1%), gait speed (1%), toe-out angle (12%), and lateral trunk lean angle (13%). There was no confounding or interaction with Kellgren and Lawrence grade of severity. CONCLUSIONS: Gait kinematics, particularly lateral trunk lean, explain substantial variation in dynamic knee joint load in patients with medial compartment knee osteoarthritis. While largely ignored in previous gait studies, the effect of lateral trunk lean should be considered in future research evaluating risk factors and interventions for progression of knee osteoarthritis.

Design and validation of an unconstrained loading system to measure the envelope of motion in the rabbit knee joint.

An unconstrained loading system was developed to measure the passive envelope of joint motion in an animal model commonly used to study ligament healing and joint arthritis. The design of the five-degree-of-freedom system allowed for unconstrained knee joint loading throughout flexion with repeated removal and reapplication of the device to a specimen. Seven New Zealand White rabbit knees were subjected to varus, valgus, internal and external loads, and the resulting envelopes of motion were recorded using an electromagnetic tracking device. Intra-specimen reproducibility was excellent when measured in one specimen, with maximal rotational differences of 0.6 and 0.3 deg between the fourth and fifth testing cycles for the varus (VR) and valgus (VL) envelopes, respectively. Similarly, the maximal internal (INT) and external (EXT) envelope differences were 0.5 and 0.4 deg, respectively, between the fourth and fifth cycles. Good inter-animal envelope reproducibility was also observed with consistent motion pathways for each loading condition. A maximal VR-VL laxity of 17.9 +/- 2.3 deg was recorded at 95 deg flexion for the seven knees tested. The maximal INT-EXT laxity of 75.2 +/- 4.8 deg occurred at 50 deg flexion. Studies on measurement reproducibility of re-applying individual testing components demonstrated a maximal error of 1.2 +/- 0.7 deg. Serial removal and re-application (test-retest) of the complete measuring system to one cadaveric knee demonstrated maximal envelope differences of less than 0.7 deg for VR-VL rotation and 2.1 deg for INT-EXT rotation. Our results demonstrate that the measuring system is reproducible and capable of accurate evaluation of knee joint motion. Baseline in vitro data were generated on normal joint kinematics for future in-vivo studies with this system, evaluating ligament healing and disease progression in arthritis models.

Thermal capsulorrhaphy for instability of the shoulder: multidirectional and posterior instabilities.

Early results of thermal capsulorrhaphy appear to be favorable and the procedure seems safe when used appropriately to enhance shoulder stability, either in isolation or combination with other arthroscopic procedures. Basic science research has shown that the capsular response to thermal energy and its effect on the mechanical properties of the tissue is dependent on both time and temperature. Additional work is needed to better understand the tissue's healing response and the time required to restore its mechanical properties. Although short-term results are encouraging, longer-term follow-up and studies cited in peer-reviewed publications are needed.

Evaluation and treatment of recurrent instability after anterior cruciate ligament reconstruction.

Revision ACL surgery has become increasingly common. Successful revision surgery requires a thorough preoperative evaluation, including a detailed history and a physical and radiographic examination. Preoperative planning is imperative for a successful outcome, as it limits the potential for repeating the errors that led to the failure of the primary procedure. This begins with a determination of the mechanism of failure. Often, a primary as well as a secondary cause of failure can be identified. Determination of the etiology of failure is the first step in a carefully constructed treatment plan, which includes the type of revision and skin incision, graft and hardware removal, tunnel placement, graft selection and fixation, and the rehabilitation protocol. The preoperative plan should have enough flexibility to accommodate unanticipated findings in the operating room. Finally, the importance of counseling the patient preoperatively regarding potential results must be emphasized. Given the complexity of revision ACL reconstruction, the patient's expectations must be adjusted to realistically match the potential for success. The goal of successful revision surgery may be only to return the patient to activities of daily living or work, especially if there is evidence of degenerative joint disease. With proper planning and attention to detail, revision ACL surgery can provide a satisfying solution to difficult cases of knee instability.

Potential complication of bioabsorbable screw fixation for osteochondritis dissecans of the knee.

The 3 cases presented describe loosening or failure of bioabsorbable screws in the treatment of osteochondritis dissecans (OCD). In case 1, a 17-year-old boy with OCD of the medial femoral condyle was treated with bioabsorbable screw fixation. Six months after surgery, the patient had an acute episode of pain with effusion. Arthroscopic examination revealed 2 of the 4 screws backed out, causing cartilage damage to the corresponding tibial plateau. The shafts of the remaining 2 screws had completely absorbed, leaving the unabsorbed screw heads as intra-articular loose bodies in the knee. Unpredictable and inconsistent degradation of the screws is believed to be the mechanism for screw back-out and cartilage damage.

Overuse tendonitis and rehabilitation.

Tendon injuries are often caused by overuse during sport or day-to-day activities. Knowledge of these injuries has grown greatly during the last several decades. We review recent literature on the structure and mechanical properties of tendons, the cause of overuse injury, and rehabilitation.