Examination of knee extensor and valgus moment arms of the patellar tendon in older individuals with and without knee osteoarthritis.

BACKGROUND: Joint moment arm is a major element that determines joint torque. This study aimed to investigate factors associated with knee extensor and valgus moment arms of the patellar tendon in older individuals with and without knee osteoarthritis. METHODS: Thirty-six participants with knee osteoarthritis (mean age, 78.1 ± 6.0 years) and 43 healthy controls (mean age, 73.0 ± 6.3 years) were analyzed. Magnetic resonance images (MRI) from the knee joint and thigh were acquired using a 3.0 T MRI scanner. The three-dimensional moment arm was defined as the distance between the contact point of the tibiofemoral joint and the patellar tendon line. The three-dimensional moment arm was decomposed into sagittal and coronal components, which were calculated as knee extensor and valgus moment arms, respectively. Quadriceps muscle volume, epicondylar width, bisect offset, Insall-Salvati ratio, and Kellgren-Lawrence grade were assessed. Multiple regression analyses were performed in the healthy control and knee osteoarthritis groups, with knee extensor and valgus moment arms as dependent variables. FINDINGS: Knee extensor moment arm was significantly associated with epicondylar width and the Insall-Salvati ratio in the healthy control group and with Kellgren-Lawrence grade, epicondylar width, and quadriceps muscle volume in the knee osteoarthritis group. Valgus knee moment arm was significantly associated with bisect offset in both the groups. INTERPRETATION: Knee size, osteoarthritis severity, and quadriceps muscle volume affect the knee extensor moment arm in knee osteoarthritis, whereas lateral patellar displacement affects the valgus knee moment arms in older individuals with and without knee osteoarthritis.

Model Properties and Clinical Application in the Finite Element Analysis of Knee Joint: A Review.

The knee is the most complex joint in the human body, including bony structures like the femur, tibia, fibula, and patella, and soft tissues like menisci, ligaments, muscles, and tendons. Complex anatomical structures of the knee joint make it difficult to conduct precise biomechanical research and explore the mechanism of movement and injury. The finite element model (FEM), as an important engineering analysis technique, has been widely used in many fields of bioengineering research. The FEM has advantages in the biomechanical analysis of objects with complex structures. Researchers can use this technology to construct a human knee joint model and perform biomechanical analysis on it. At the same time, finite element analysis can effectively evaluate variables such as stress, strain, displacement, and rotation, helping to predict injury mechanisms and optimize surgical techniques, which make up for the shortcomings of traditional biomechanics experimental research. However, few papers introduce what material properties should be selected for each anatomic structure of knee FEM to meet different research purposes. Based on previous finite element studies of the knee joint, this paper summarizes various modeling strategies and applications, serving as a reference for constructing knee joint models and research design.

Strength and passive stiffness of the quadriceps are associated with patellar alignment in older adults with knee pain.

BACKGROUND: Maintaining normal patellar alignment is important for knee health. Altered activation of individual quadriceps muscles have been found related to patellar alignment. However, the relationships between strength and passive stiffness of the quadriceps and patellar alignment remains unexplored. METHODS: Participants aged between 60 and 80 years with activity-induced knee pain were recruited. Knee pain was quantified using an 11-point numeric rating scale. Quadriceps strength was assessed using a Cybex dynamometer and passive stiffness of rectus femoris, vastus lateralis, and vastus medialis were measured by shear-wave ultrasound elastography. Patellar alignments were assessed using MR imaging. Linear regression was used to examine relationships between quadriceps properties and patellar alignments with and without controlling for potential covariates. FINDINGS: Ninety-two eligible participants were assessed (71.7% females, age: 65.6 ± 3.8 years; pain scale: 4.6 ± 2.0), most of whom had knee pain during stair climbing (85.9%). We found that 17% of patellar lateral tilt angle could be explained by lower quadriceps strength (adjusted R2 = 0.117; P < 0.001), especially in females (R2 = 0.281; P < 0.001; adjusted R2 = 0.211; P < 0.001). In addition, a higher stiffness ratio of vastus lateralis/medialis accounted for 12% of patellar lateral displacement (adjusted R2 = 0.112; P = 0.008). INTERPRETATION: Quadriceps strength and relative stiffness of lateral to medial heads are associated with patellar alignment in older adults with knee pain. It suggests that quadriceps weakness and relatively stiffer lateral quadriceps may be risk factors related to patellar malalignments in the elderly.

Patellar malalignment: A common disorder associated with knee pain.

Pain-associated knee joint disorders are common in daily life. Practically, knee pain should be divided into the origin from the isolated tibiofemoral (TF), isolated patellofemoral (PF) joint, or a combination thereof. The TF joint controls the actions of level walking, while the PF joint controls knee flexion-extension. Owing to its sufficient inherent stability, non-traumatic disorders of the isolated TF joint in young individuals are uncommon. In contrast, because of its insufficient inherent stability, non-traumatic disorders of the isolated PF joint are common in young individuals. Patellar malalignment (PM) associated with knee pain is common in all age groups, and the most common predisposing factor is imbalanced peripatellar soft-tissue tension. The outward forces acting on the patella are caused by pulling from the quadriceps femoris during knee flexion to extension (manifested by the quadriceps angle [Q-angle]), and sliding backward of the iliotibial band (ITB) during knee extension to flexion. Once the muscle power of the vastus medialis (especially the vastus medialis obliquus [VMO]) decreases, which lowers the counteracting effect against outward forces, the patella displaces or rotates laterally. The reduced contact surface between the patella and the femoral condyle significantly increases the compressive pressure and injures the articular cartilage. Subsequently, progressive PF degeneration occurs. Although other factors may also cause PM, they are relatively uncommon. In principle, nonsurgical treatment of PM should be considered first, while surgical treatment should follow established indications. Some nonsurgical techniques are currently widely used that feature high satisfaction rates. Surgical techniques are continuously being developed, and their success rates have gradually improved. This study aimed to review the current literature for relevant studies and report related publications of the author's institution to emphasize the universality and importance of PM management. Conceptually, simply focusing on problems of the TF joint cannot treat all knee disorders.

Comparison between conventional MRI and weight-bearing positional MRI reveals important differences in radiological measurements of the patellofemoral joint.

OBJECTIVE: To compare radiological measurements of the patellofemoral joint (PFJ) morphology and measurement reproducibility across the following scanning modalities: (a) 3 T supine MRI, (b) 0.25 T supine MRI and (c) standing 0.25 T MRI. METHODS: Forty patients referred to MRI of the knee were scanned by high field 3 T MRI in supine position and low field 0.25 T positional (pMRI) in supine and standing positions. Radiological measurements for assessment of femoral trochlear morphology, patellar tracking, patellar height and knee flexion angle were compared across scanning situations by one-way repeated-measures ANOVA. Measurement reliability and agreement were assessed by calculation of ICC, SEM and MDC. RESULTS: Patellar tracking differed across scanning situations, particularly between 3.0 T supine and 0.25 T standing position. Mean differences are the following: patella bisect offset (PBO): 9.6%, p ≤ 0.001; patellar tilt angle (PTA): 3.1°, p ≤ 0.001; tibial tuberosity-trochlear groove distance (TT-TG): 2.7 mm, p ≤ 0.001). Measurements revealed slight knee joint flexion in supine and slight hyperextension in the standing position (MD: 9.3°, P ≤ 0.001), likely related to the observed differences in patellar tracking. Reproducibility was comparable across MRI field strengths. In general, PBO, PTA and TT-TG were the most robust measurements in terms of reproducibility and agreement across scanning situations (ICC range: 0.85-0.94). CONCLUSION: Significant differences in important patellofemoral morphology measurements were observed between supine and standing MRI scanning positions. These were unlikely due to physiological factors such as changes in joint loading but rather induced by slight differences in knee flexion angle. This emphasises the need to standardise knee positioning during scanning, particularly for weight-bearing positional MRI before clinical use.

The Nonintuitive Contributions of Individual Quadriceps Muscles to Patellar Tracking.

The purpose of this study was to quantify the contribution of the individual quadriceps muscles to patellar tracking. The individual and/or combined quadriceps muscles were activated in rabbits (n = 6) during computer-controlled flexion/extension of the knee. Three-dimensional patellar tracking was measured for the vastus lateralis, vastus medialis, and rectus femoris when activated alone and when activated simultaneously at different frequencies, producing a range of knee extensor torques. Patellar tracking changed substantially as a function of knee extensor torque and differed between muscles. Specifically, when all quadriceps muscles were activated simultaneously, the patella shifted more medially and proximally and rotated and tilted more medially compared with when vastus lateralis and rectus femoris were activated alone (P < .05), whereas vastus medialis activation alone produced a similar tracking pattern to that observed when all quadriceps muscles were activated simultaneously. Furthermore, patellar tracking for a given muscle condition shifted more medially and proximally and rotated and tilted more medially with increasing knee extensor torques across the entire range of knee joint angles. The authors conclude that patellar tracking depends crucially on knee extensor force/torque and that vastus medialis affects patellar tracking in a distinctly different way than vastus lateralis and rectus femoris, which produce similar tracking patterns.

Adolescent perspectives on participating in a feasibility trial investigating shoe inserts for patellofemoral pain.

BACKGROUND: Patellofemoral pain (PFP) affects one-quarter of adolescents, yet there are few evidence-informed recommendations to treat PFP in this population. HAPPi Kneecaps! is a randomised, controlled, participant- and assessor-blind, parallel-group feasibility trial of shoe inserts for adolescents with PFP. The aim of this qualitative study was to explore adolescents' perspectives of participating in HAPPi Kneecaps!. METHODS: All 36 adolescents with PFP from the HAPPi Kneecaps! study were invited to participate in semi-structured interviews. We used a descriptive qualitative methodology underpinned by a relativist framework to investigate adolescents' perspectives on participating in the trial. Inductive thematic analysis was used to examine patterns regarding how each adolescent experienced the HAPPi Kneecaps! study within their social, cultural, and historical contexts. RESULTS: 14 out of 36 HAPPi Kneecaps! participants provided consent and participated in interviews (12 females; mean [SD] age 14.9 [2.4] years). Overall, most adolescents responded positively when discussing their experience, such as improvements in their knee pain and satisfaction with how the study was run. Major themes that were generated from the analysis and feedback were: (1) shoe inserts require little effort to use; (2) perceptions of the program were generally positive; (3) participation in the trial could be made easier; (4) warm weather matters; and (5) life happens. CONCLUSION: Adolescents with PFP who participated in the HAPPi Kneecaps! study found that shoe inserts were easy to wear. Most adolescents experienced an improvement in their symptoms and enhanced participation in sport and exercise. Adolescents with PFP prefer an option for warmer climates (e.g. flip flops or sandals), access to online logbooks, and clinicians who are easily accessible. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry (ANZCTR): ACTRN12619000957190 . Date registered: 8/07/2019.

Articular contact motion at the knee during daily activities.

We combined mobile biplane X-ray imaging and magnetic resonance imaging to measure the regions of articular cartilage contact and cartilage thickness at the tibiofemoral and patellofemoral joints during six functional activities: standing, level walking, downhill walking, stair ascent, stair descent, and open-chain (non-weight-bearing) knee flexion. The contact centers traced similar paths on the medial and lateral femoral condyles, femoral trochlea, and patellar facet in all activities while their locations on the tibial plateau were more varied. The translations of the contact centers on the femur and patella were tightly coupled to the tibiofemoral flexion angle in all activities (r2 > 0.95) whereas those on the tibia were only moderately related to the flexion angle (r2 > 0.62). The regions of contacting cartilage were significantly thicker than the regions of non-contacting cartilage on the patella, femoral trochlea, and the medial and lateral tibial plateaus in all activities (p < 0.001). There were no significant differences in thickness between contacting and non-contacting cartilage on the medial and lateral femoral condyles in all activities, except open-chain knee flexion. Our results provide partial support for the proposition that cartilage thickness is adapted to joint load and do not exclude the possibility that other factors, such as joint congruence, also play a role in regulating the structure and organization of healthy cartilage. The data obtained in this study may serve as a guide when evaluating articular contact motion in osteoarthritic and reconstructed knees.

A Sagittal Patellar Angle Linear Equation Reflecting Patellofemoral Kinematics: Evaluation of Patellar Height at any Degree of Knee Flexion Angle.

OBJECTIVE: To confirm whether a novel sagittal patellar angle linear equation used for evaluating patellar height by calculating expected sagittal patellar angle (SPA) at any degree of knee flexion angle is suitable for patients older than 17 years and its reliability compared with other commonly used methods. METHODS: From September 2016 to September 2019, a total number of 202 consecutive outpatients' knee lateral X-ray radiographs were retrospectively measured and evaluated using a recently proposed linear equation Y = 1.94 + 0.74 × knee flexion(KF) angle. Patients were divided by ages into ayounger group, whose ages were between 17-49 years, and an older group, whose ages were older than 49 years, which has not been validated in the original study. Parameters such as KF, SPA, patella and patella tendon length and so on were measured on computer with picture archiving and communication system by two independent observers at an interval of 1 month. Insall-Salvati (IS) index, Caton-Deschamps (CD) index and Y value, correlation coefficients were calculated and compared using SPSS 22.0 software. RESULTS: In the younger group, 143 patients (165 knees) were included, ages were 17-49 (31.62 ± 11.38) years, males/females were 70 (48.95%)/73 (51.05%), left knees/right knees were 83 (50.30%)/82 (49.70%), mean value of Y was 31.50° ± 10.07°, and SPA was 34.38° ± 12.38°, mean value of IS was 1.06 ± 0.17, mean value of CD was 1.04 ± 0.18. While in older group, 59 patients (78 knees) were included, ages were 50-60 (mean 54.61 ± 2.99) years, there were 32 males (54.24%) and 27 females (45.76%), 42 knees were left (53.85%) and 36 knees were right (46.15%), mean values of Y and SPA were 25.90° ± 11.55° and 29.36° ± 14.22°, mean IS index in older group was 1.06 ± 0.18, mean CD index was 1.00 ± 0.16. Intra- and inter-observer reliabilities of Y in younger and older groups were 0.999, 0.999, 1.000 and 0.999, meaning high reliability and reproducibility, but low Pearson's correlation coefficients with IS and CD index were showed as -0.213 and - 0.216 in younger group and - 0.113 and - 0.316 in older group. CONCLUSIONS: In patients older than 17 years, the linear equation Y = 1.94 + 0.74 × KF is a reliable and practical method to evaluate SPA regardless of age and knee flexion angle, but has weak correlation coefficients with the IS and CD index.

Modern femoral component design in total knee arthroplasty shows a lower patellar contact force during knee flexion compared with its predecessor.

BACKGROUND: The relationship between the femoral component design in total knee arthroplasty (TKA) and the patellofemoral contact force, as well as the soft tissue balance, has not been well reported thus far. METHODS: Twenty-eight mobile-bearing posterior-stabilized (PS) TKAs using the traditional model (PFC Sigma) and 27 mobile-bearing PS TKAs using the latest model (Attune) were included. Surgeries were performed using the measured resection technique assisted with the computed tomography (CT)-based free-hand navigation system. After all the trial components were placed, patellar contact forces on the medial and lateral sides were measured using two uniaxial ultrathin force transducers with the knee at 0°, 10°, 30°, 60°, 90°, 120°, and 135° of flexion. The joint component gap and the varus ligament balance of the femorotibial joint were also measured. The non-paired Student's t-test was conducted to compare the values of the two groups. RESULTS: The medial patellar contact force was significantly lower for Attune group than for PFC Sigma group at 120° of knee flexion (P = 0.0058). The lateral patellar contact force was also significantly lower for Attune group than PFC Sigma group at 120° and 135° of knee flexion (P = 0.0068 and P = 0.036). The joint component gap, as well as the varus ligament balance, showed no statistically significant difference between the two groups. CONCLUSIONS: Reduced thickness and width of the anterior flange of the femoral component in the Attune may play a role in low patellar contact force.

Six-Degree-of-Freedom Tibiofemoral and Patellofemoral Joint Motion During Activities of Daily Living.

The purpose of this study was to measure the three-dimensional movements of the femur, tibia and patella in healthy young people during activities of daily living. A mobile biplane X-ray imaging system was used to obtain simultaneous measurements of six-degree-of-freedom (6-DOF) tibiofemoral and patellofemoral kinematics and femoral condylar motion in ten participants during standing, level walking, downhill walking, stair ascent, stair descent and open-chain (non-weightbearing) knee flexion. Seven of the eleven secondary motions at the knee-three translations at the tibiofemoral joint, three translations at the patellofemoral joint, and patellar flexion-were coupled to the tibiofemoral flexion angle (r2 ≥ 0.71). Tibial internal-external rotation, tibial abduction-adduction, patellar rotation, and patellar tilt were each weakly related to the tibiofemoral flexion angle (r2 ≤ 0.45). The displacements of the femoral condyles were also coupled to the tibiofemoral flexion angle (r2 ≥ 0.70), with the lateral condyle translating further on the tibial plateau than the medial condyle. The center of rotation of the tibiofemoral joint in the transverse plane was located on the medial side in all activities. These findings expand our understanding of the kinematic function of the healthy knee and may be relevant to a range of applications in biomechanics, including the design of prosthetic knee implants and the development of knee models for use in full-body simulations of movement.

Patellar component size effects patellar tilt in total knee arthroplasty with patellar resurfacing.

PURPOSE: Patellar component positioning and patellofemoral kinematics are of great importance in total knee arthroplasty (TKA). The factors influencing patellar tilt are femoral rotation and lateral patellar release. However, the effect of patellar component size remains unknown. The aim of this study was to evaluate the intra-operative risk factors for patellar tilt, particularly the effect of the patellar component size. The hypothesis was that increasing the patellar component size would reduce the risk of patellar tilt. METHODS: 878 primary TKAs with patellar resurfacing were included between January 2015 and October 2018. Analysis was performed at 1-year postoperatively on patients categorized into two groups: patellar tilt (PT) and no patellar tilt (NPT). A multivariate analysis was performed for the effect of patellar component size, femoral rotation, femoral overbuilding, patellar thickness and lateral release on patellar tilt risk. Secondary analysis was performed for any difference in clinical outcomes and revision rates between groups. RESULTS: Multivariate analysis showed that increasing the patellar component size decreased the risk of patellar tilt by 37% (p < 0.001). Placing the femoral component at 3° of external rotation decreased the risk of patellar tilt by 67% (p < 0.001). Secondary analysis showed better clinical outcomes in the NPT group, especially regarding global satisfaction, and KSS objective and subjective scores. The revision for any cause was less in the NPT group (p = 0.019). The cause for TKA revision was related to the patellar in 11% of cases in the NPT group and 65% in the PT group (p < 0.001). CONCLUSION: Increased patellar component size and positioning the femoral component in external rotation decreases the risk of patellar tilt, improves clinical outcomes and decreases the rate of surgical revision. LEVEL OF EVIDENCE: III.

Development of an innovative measurement method for patellar tracking disorder.

In this study, we investigated whether the measurement of patellar tracking can be used as a diagnostic parameter of patellofemoral joint disease. Patellar tracking is defined as the movement of the patella in relation to the femorotibial joint within the full range of flexion and extension of the knee joint. The PubMed, EMBASE, Medline, PsychINFO, and AMED databases were used to find relevant articles. Analyzed were the patellar tracking coordinate system and the measurement objects, precision, methods used in those studies, as well as the results obtained. Origin points for coordinate systems varied across the studies. The research object and methods of patellar tracking varied in the studies. Most studies focused on a static description of the internal and external displacement and the internal and external inclination. The in vivo, noninvasive, and six degrees of freedom evaluation of patellar tracking reflect patellar motion more comprehensively, though each of these methods does so in different ways. Dynamic and quantitative evaluation of patellar tracking is still lacking in clinical work. Accurate and quantitative patellar tracking measurement could provide clinicians with a comprehensive evaluation of the stability of the knee joint.

Effects of quadriceps angle on patellofemoral contact pressure.

BACKGROUND: An inappropriate Q angle may affect the biomechanics of the canine patellofemoral joint. OBJECTIVES: The purpose of this study was to evaluate the effects of changes in quadriceps angle (Q angle) on patellofemoral joint pressure distribution in dogs. METHODS: Eight stifles were positioned at 45, 60, 75, 90, 105, and 120° of flexion in vitro, and 30% body weight was applied through the quadriceps. Patellofemoral contact pressure distribution was mapped and quantified using pressure-sensitive film. For the pressure area, mean pressure, peak pressure, medial peak pressure, and lateral peak pressure, differences between groups according to conditions for changing the Q angle were statistically compared. RESULTS: Increases of 10° of the Q angle result in increases in the pressure area (P = 0.04), mean pressure (P = 0.003), peak pressure, and medial peak pressure (P ≤ 0.01). Increasing the Q angle by 20° increases the pressure area (P = 0.021), mean pressure (P ≤ 0.001), peak pressure (P ≤ 0.01), and medial peak pressure (P ≤ 0.01) significantly, and shows higher mean (P ≤ 0.001) and peak pressures than increasing by 10°. Decreasing the Q angle increases the mean pressure (P = 0.013), peak pressure, and lateral peak pressure (P ≤ 0.001). CONCLUSIONS: Both increases and decreases in the Q angle were associated with increased peak patellofemoral pressure, which could contribute to the overloading of the cartilage. Therefore, the abnormal Q angle should be corrected to the physiologically normal value during patellar luxation repair and overcorrection should be avoided.

Correlation of T2* relaxation times of the retropatellar cartilage with tibial tuberosity-trochlea groove distance in professional soccer players.

The tibial tuberosity-trochlear groove (TT-TG) distance is a radiographic measurement that is used to quantify malalignment of the patellofemoral joint (PFJ) in cross-sectional imaging. There is an ongoing debate about the impact of the TT-TG-distance on lateral patellar instability and the initiating of cartilage degeneration. In this prospective study, the association of T2* relaxation times and TT-TG distances in professional soccer players was analyzed. 36 knees of 18 professional soccer players (age: 21 ± 2.8 years) were evaluated. Participants underwent knee MRI at 3 T. For qualitative image analysis, fat-saturated 2D PD-weighted Fast Spin Echo (FSE) and T1-weighted FSE sequences were used. For quantitative analysis, T2* measurements in 3D data acquisitions were performed. In a qualitative analysis there was no structural cartilage damage and no abnormalities of the patellar and trochlea shape. The highest T2* values (26.7 ± 5.9 ms) were observed in the central compartment of the patella. The mean TT-TG distance was 10 ± 4 mm (range 3-20 mm). There was no significant correlation between TT-TG distance and T2* relaxation times in all three compartments of the retropatellar cartilage. Our study shows that so long as patellar and trochlear morphology is normal, TT-TG distance alone does not affect the tissue structure of the retropatellar cartilage in professional soccer players.

Mathematical model of patella T-reflex and clinical evaluation with Ashworth scales.

Spasticity is one of the major problems that arise in different neurological diseases and seriously affect the quality of human life. Research on the understanding of mechanism of spasticity remains as important as the studies on the spasticity therapy and rehabilitation. In this study, the spasticity mechanism which develops concerning the upper motor neuron lesions is investigated by modelling "Patella tendon reflex triggered patella pendulum". The mathematical model based on the pendulum phenomenon is developed by solving the curve-fitting problem as finding the curve that best fits a set of data points. Electrophysiological and dynamic measurement data were taken from 76 spastic subjects and 20 healthy participants. The mathematical model is determined by the morphological properties of the goniometric variations. The results denote that the mathematical model containing two clinically relevant parameters -frequency component of the damped oscillatory motion defined as "f 0 " with the maximum angle of the reflex defined as "a 0 " ensures to distinguish spasticity from healthy subjects.

A reliable Q angle measurement using a standardized protocol.

BACKGROUND: Studies have shown that Q angle measurements were unreliable. Imaging studies have largely replaced the Q angle for measuring tibial tubercle lateralization. Creating a standardized protocol to measure the Q angle, with normative values, would provide a reliable reference without expensive imaging techniques. METHODS: Thirty men and 27 women without history of knee problems or family history of dislocating kneecaps were subjects. Exclusion criteria were: patellofemoral abnormalities upon examination. We measured the Q angles of both knees using a standardized protocol and a long-armed goniometer. These data were analyzed to calculate normative values. RESULTS: For all subjects, the mean was 14.8° (≈15°), 95% confidence interval (CI): ±5.4°. The male mean was 13.5°, 95% CI: ±5.2°. The female mean was 15.9°, 95% CI: ±4.8°. There was no significant difference between the right and left knees of the males (p = 0.52), nor of the females (p = 0.62), Beta = 0.14. The 2.4° difference between male and female means was due to the average height difference between the men and women. CONCLUSIONS: This study provides a standardized Q angle measurement protocol to assess tibial tubercle lateralization at a patient's first encounter (and intra-operatively) without resorting to expensive imaging studies. These values provide a reliable reference for clinical comparison, and will allow all clinicians and sports medicine personnel to assess tubercle lateralization with reliability and validity. When using this protocol, the term "Standard Q Angle" (SQA) should be used, to avoid confusion with other measurement protocols.

Quantifying the biochemical state of knee cartilage in response to running using T1rho magnetic resonance imaging.

Roughly 20% of Americans run annually, yet how this exercise influences knee cartilage health is poorly understood. To address this question, quantitative magnetic resonance imaging (MRI) can be used to infer the biochemical state of cartilage. Specifically, T1rho relaxation times are inversely related to the proteoglycan concentration in cartilage. In this study, T1rho MRI was performed on the dominant knee of eight asymptomatic, male runners before, immediately after, and 24 hours after running 3 and 10 miles. Overall, (mean ± SEM) patellar, tibial, and femoral cartilage T1rho relaxation times significantly decreased immediately after running 3 (65 ± 3 ms to 62 ± 3 ms; p = 0.04) and 10 (69 ± 4 ms to 62 ± 3 ms; p < 0.001) miles. No significant differences between pre-exercise and recovery T1rho values were observed for either distance (3 mile: p = 0.8; 10 mile: p = 0.08). Percent decreases in T1rho relaxation times were significantly larger following 10 mile runs as compared to 3 mile runs (11 ± 1% vs. 4 ± 1%; p = 0.02). This data suggests that alterations to the relative proteoglycan concentration of knee cartilage due to water flow are mitigated within 24 hours of running up to 10 miles. This information may inform safe exercise and recovery protocols in asymptomatic male runners by characterizing running-induced changes in knee cartilage composition.

Patellar facet ratio affects knee pain, stair climbing and stair descent after TKA without patellar resurfacing.

PURPOSE: To determine whether knee pain or functional impairment after total knee arthroplasty (TKA) without patellar resurfacing are correlated with preoperative patellar morphology or postoperative patellar orientation. The hypotheses were that patellar shape, increased tilt and lateral displacement would be associated with pain and functional impairment. METHODS: From a consecutive series of 152 knees that received a cemented postero-stabilized TKA, the Oxford Knee Score (OKS) and the Knee injury and Osteoarthritis Outcome Score (KOOS) were collected at a minimum follow-up of 12 months. Uni- and multi-variable linear regression analyses were performed to determine associations between the collected clinical scores and patient demographics and patellar morphology, measured from pre- and post-operative frontal, lateral and skyline view radiographs. RESULTS: The OKS was 75 ± 23, whereas the KOOS pain, stair climbing, and descent were respectively 77 ± 24, 3.9 ± 1.1 and 3.8 ± 1.2. OKS was not associated with any radiographic outcomes, whereas KOOS pain was better for knees with larger medial patellar facets. The KOOS stair climbing and descent were also better for knees with larger medial patellar facets. CONCLUSION: The findings of this study partly confirm the hypotheses that pain and functional impairments after TKA without patellar resurfacing are associated with patellar shape. No association was revealed between postoperative patellar orientation and function nor pain. Quantitative consideration of patellar congruency could therefore prevent pain and improve function after TKA without patellar resurfacing. LEVEL OF EVIDENCE: Retrospective study, Level III.

Development and validation of a robust patellar reference coordinate system for biomechanical and clinical studies.

BACKGROUND: This study aimed to develop and validate a reference coordinate system for the human patella, based on the registration of bony landmarks on a computed tomography (CT) scan. METHODS: Thirty-three native cadaveric specimens were scanned, and an observer marked a set of seven anatomical landmarks on each of them. Such markers were used to define the reference coordinate system. In order to validate its robustness, statistical distribution of the point registration was then studied. Afterwards, three different observers marked the anatomical landmarks on a sub-sample of six specimens and the intra-observer and inter-observer variability of the point registration was performed. RESULTS: Results of this study showed the highest values to be 1.46 mm (intra) and 4.08 mm (inter), both observed for the patellar ridge top. The intra-class correlation coefficient (ICC) for inter-observer variability ranked higher than 0.8 for all the landmarks used for the identification of the reference frame, and ranged from 0.4-0.9 for other landmarks. CONCLUSIONS: This study demonstrates low intra-observer and inter-observer variability in the CT registration of landmarks that define and validate a robust coordinate system of the patella that could be used to perform accurate biomechanical and clinical studies.