Patterns of femorotibial cartilage loss in knees with neutral, varus, and valgus alignment

The mediation effects of malalignment on the relation of sex to the risk of incidence tibiofemoral osteoarthritis

OBJECTIVE

To investigate to what extent the higher risk of tibiofemoral radiographic osteoarthritis (TFROA) in females vs. males can be explained by knee malalignment.

DESIGN

Using data from Multicenter Osteoarthritis Study (MOST) and Osteoarthritis Initiative (OAI), we examined the relation of sex to the incident medial and lateral TFROA and performed mediation analyses to assess to what extent varus and valgus malalignments account for sex differences in the incident medial or lateral TFROA.

RESULTS

Of the 3462 knees without medial and lateral TFROA in MOST, the 7-year risks of medial and lateral TFROA were 16.9% and 10.0% in females, and 15.8% and 4.2% in males, respectively. Females had 2.31-fold (95% confidence interval [95% CI]: 1.73 to 3.08) higher incident lateral TFROA than males, and the relative risk (RR) of the indirect effect of sex on lateral TFROA through valgus malalignment was 1.15 (95% CI: 1.09 to 1.20), accounting for 23% of its total effect on lateral TFROA. In OAI (n = 3095 knees), females had 1.54-fold (95% CI: 1.15 to 2.04) higher incident lateral TFROA than males, and RR of the indirect effect of sex on lateral TFROA through valgus malalignment was 1.10 (95% CI: 1.04 to 1.21), accounting for 26% of its total effect on lateral TFROA. No apparent sex difference in the incident medial TFROA was found in MOST (RR = 1.05, 95% CI: 0.89 to 1.25) or OAI (RR = 1.02, 95% CI: 0.84 to 1.19).

CONCLUSION

Females had a higher risk of developing lateral TFROA than males; however, valgus malalignment only modestly explained such a difference.

Modulation of early osteoarthritis by tibiofemoral re-alignment in sheep

OBJECTIVE

To investigate whether tibiofemoral alignment influences early knee osteoarthritis (OA). We hypothesized that varus overload exacerbates early degenerative osteochondral changes, and that valgus underload diminishes early OA.

METHOD

Normal, over- and underload were induced by altering alignment via high tibial osteotomy in adult sheep (n = 8 each). Simultaneously, OA was induced by partial medial anterior meniscectomy. At 6 weeks postoperatively, OA was examined in five individual subregions of the medial tibial plateau using Kellgren-Lawrence grading, quantification of macroscopic OA, semiquantitative histopathological OA and immunohistochemical type-II collagen, ADAMTS-5, and MMP-13 scoring, biochemical determination of DNA and proteoglycan contents, and micro-computed tomographic evaluation of the subchondral bone.

RESULTS

Multivariate analyses revealed that OA cartilaginous changes had a temporal priority over subchondral bone changes. Underload inhibited early cartilage degeneration in a characteristic topographic pattern (P ≥ 0.0983 vs. normal), in particular below the meniscal damage, avoided alterations of the subarticular spongiosa (P ≥ 0.162 vs. normal), and prevented the disturbance of otherwise normal osteochondral correlations. Overload induced early alterations of the subchondral bone plate microstructure towards osteopenia, including significantly decreased percent bone volume and increased bone surface-to-volume ratio (all P ≤ 0.0359 vs. normal).

CONCLUSION

The data provide high-resolution evidence that tibiofemoral alignment modulates early OA induced by a medial meniscus injury in adult sheep. Since underload inhibits early OA, these data also support the clinical value of strategies to reduce the load in an affected knee compartment to possibly decelerate structural OA progression.

Which Knee Phenotypes Exhibit the Strongest Correlation With Cartilage Degeneration?

BACKGROUND

Although articular wear has been thoroughly investigated, the effects of abnormal limb alignment on cartilage degeneration over time remain poorly understood. An exact assessment of the correlation between lower limb alignment abnormalities and MRI-observed articular degradation may be helpful for understanding the progression of osteoarthritis and planning future treatment.

QUESTION/PURPOSE

In patients with moderate to advanced osteoarthritis, (1) is there a correlation between overall alignment of the knee and the location of cartilage degradation over time, as measured by cartilage metrics on MRI? (2) Is there a correlation between tibial alignment and the location of cartilage degradation over time, as measured by cartilage metrics on MRI? (3) Is there a correlation between femoral alignment and the location of cartilage degradation over time, as measured by cartilage metrics on MRI?

METHODS

Between April 2020 and September 2022, we retrospectively evaluated 3106 patients aged 45 to 79 years who were at risk of experiencing knee osteoarthritis. Of those, we considered as potentially eligible 600 symptomatic index knees with radiographic evidence of osteoarthritis-Kellgren-Lawrence Grades 2 or 3-at the baseline visit. Of those, 22% (134 of 600) were excluded because of a lack of proper alignment measurements, leaving 466 knees with measurements of radiologic alignment angles and quantitative MRI cartilage measurements of 16 subregions of the femorotibial compartment at baseline and 12 and 24 months, and 64 knees at the 48-month visit for investigation in the current study. Data regarding cartilage measurements of the patellofemoral compartment were not available for analysis. The knees were categorized into one of the possible 25 different phenotypes of the lower extremity established by previous research, based on the neutral, valgus, or varus distal mechanical angle of the femur and proximal tibial mechanical angle on full-limb radiographs. We applied ANOVA to estimate the effect size of the overall, femoral, and tibial alignments on the location of cartilage degradation over time, as measured by cartilage metrics on MRI.

RESULTS

We found that the overall combinations of a valgus femur with valgus tibia or a valgus femur with varus tibia were associated with the highest loss of cartilage in the internal medial tibial subregion and anterior lateral tibial subregion (η 2 p = 0.39 and 0.17, respectively). For the tibia, we found that the combination of a valgus femur with valgus tibia was associated with an increase in the area of subchondral bone denuded of cartilage in the central lateral tibial subregion (η 2 p = 0.2). For the femur, we found that the combination of a valgus femur with valgus tibia was associated with loss of cartilage thickness in the central weightbearing lateral femorotibial compartment (η 2 p = 0.15).

CONCLUSION

We found that certain alignment patterns are associated with rapid deterioration of cartilage and exposure of subchondral bone, even over short time periods. In particular, the valgus femur with valgus tibia and valgus femur with varus tibia phenotypes deserve special attention, because they exhibited a strong, atypical correlation with the internal medial tibial subregion and anterior lateral tibial subregion, respectively. This is important because valgus and varus malalignment cause isolated lateral and medial compartment disease, respectively. Therefore, these findings suggest that a more individualized approach for limb axis deformities is valuable, and hint at a more meticulous radiologic and clinical investigation, perhaps using different imaging modalities, especially when assessing the exact cartilage state and planning an intervention. Future studies, ideally biomechanical, might help in assessing the long-term effects of the various phenotypes on cartilage degradation and their relevance in reconstructive surgery.

LEVEL OF EVIDENCE

Level II, prognostic study.

Quantitative measurement of cartilage morphology in osteoarthritis: current knowledge and future directions

Quantitative measures of cartilage morphology ("cartilage morphometry") extracted from high resolution 3D magnetic resonance imaging (MRI) sequences have been shown to be sensitive to osteoarthritis (OA)-related change and also to treatment interventions. Cartilage morphometry is therefore nowadays widely used as outcome measure for observational studies and randomized interventional clinical trials. The objective of this narrative review is to summarize the current status of cartilage morphometry in OA research, to provide insights into aspects relevant for the design of future studies and clinical trials, and to give an outlook on future developments. It covers the aspects related to the acquisition of MRIs suitable for cartilage morphometry, the analysis techniques needed for deriving quantitative measures from the MRIs, the quality assurance required for providing reliable cartilage measures, and the appropriate participant recruitment criteria for the enrichment of study cohorts with knees likely to show structural progression. Finally, it provides an overview over recent clinical trials that relied on cartilage morphometry as a structural outcome measure for evaluating the efficacy of disease-modifying OA drugs (DMOAD).

Changes in coronal knee-alignment parameters during the osteoarthritis process in the varus knee

OBJECTIVES

The idea to aim for an "individualized" alignment, whereby the constitutional alignment is restored, has gained much interest among knee surgeons. This requires insight into the prediseased, natural alignment of our patients' knees. The aim of this study is (1) to determine how the hip-knee-ankle (HKA) angle is influenced during the arthritic process and (2) to investigate the correlation between joint line changes and the progression of osteoarthritis (OA). It is our hypothesis that the most pronounced coronal parameter changes appear at the proximal tibia and at the joint line.

METHODS

One hundred sequential full-length X-rays with a minimum follow-up of 1 year were retrospectively reviewed from a radiographic joint database. Patients had to be at least 50 years of age needed to have an HKA angle of more than 1.3° varus to be included. Patients with ipsilateral total hip arthroplasty, femoral or tibial fracture, osteotomy, or ligamentous repair were excluded. Fifteen alignment parameters were investigated on the sequential full-length X-rays. Moreover, the relationship between the alignment parameters and the Kellgren-Lawrence grade (KL grade) was determined by using linear mixed models.

RESULTS

A progressive KL grade is associated with an increase of the HKA (p < 0.001). Mostly, HKA differs due to decrease of the medial tibial plateau (MPTA) angle (0.93°) and an increase of the joint line angle (JLCA) (0.86°). The mLDFA demonstrated the most pronounced changes in the beginning of OA (KL grade 1-2) (p = 0.049). In particular, the MPTA becomes considerably smaller (p = 0.004) in the later stage of OA (KL grade 3). Also, a progressive increase of the JLCA (p < 0.001) is observed upwards of KL grade 3.

CONCLUSION

By comparing consecutive full-length X-rays in the same patients, it is possible to define the coronal alignment changes during the arthritic process. The HKA angle increases according the arthritic progression, whereby the most pronounced changes appear at the proximal tibia (MPTA) and at the joint line (JLCA).The alignment changes in varus OA knees can be divided in three stadia: (1) erosion of the distal medial femoral condyle, (2) erosion of the medial tibial plateau, and (3) a progressive increase of the joint line angle.

LEVEL OF EVIDENCE

Therapeutic Study, Level III.

Relationships between tibial articular cartilage, in vivo external joint moments and static alignment in end-stage knee osteoarthritis: A micro-CT study

Biomechanical factors (e.g., joint loading) have a significant role in the progression of osteoarthritis (OA). However, some relationships between in vivo joint loading indices and tibial cartilage thickness are conflicting. This study investigated relationships between pre-operative in vivo external knee joint moments, joint alignment and regional tibial cartilage thickness using micro-CT in subjects with end-stage knee OA. Tibial plateaus from 25 patients that underwent knee replacement for OA were micro-CT scanned (17 µm/voxel). Prior to surgery, subjects underwent gait analysis to calculate external knee moments. The mechanical axis deviation (MAD) was obtained from pre-operative radiographs. Cartilage thickness (Cart.Th) was analyzed from micro-CT images, in anteromedial, anterolateral, posteromedial and posterolateral subregions of interest. Medial-to-lateral Cart.Th ratios were also explored. Relationships between Cart.Th and joint loading indices were examined using Pearson's correlations. Significant correlations were found between Cart.Th and joint loading indices, positive anteromedially with the first peak knee adduction moment (r = 0.55, p < 0.01) and external rotation moment (ERM; r = 0.52, p < 0.01), and negative with MAD (r = -0.76, p < 0.001). In the lateral regions, these correlations had opposite signs. The medial-to-lateral Cart.Th ratio correlated strongly with ERM (r = 0.63, p = 0.001) and MAD (r = -0.75, p < 0.001). Joint loading indices correlated with regional cartilage thickness values and their medial-to-lateral ratios in end-stage knee OA subjects, with higher regional loads corresponding to thinner cartilage. These relationships have the opposite sign compared to the subchondral bone microarchitecture found in our previous study on the same specimens, which may suggest a complementary bone-cartilage interplay in response to loading.

Distal femoral phenotypes in Asian varus osteoarthritic knees

PURPOSE

There has been a general consensus regarding the varus phenotype of the proximal tibia in osteoarthritic patients with varus knee alignment of the whole limb. However, a valgus phenotype of the distal femur may occur in osteoarthritic patients with varus knee alignment. This study evaluated the distal femur phenotype in varus osteoarthritic knees.

METHODS

This study included 128 patients who underwent primary total knee arthroplasty (TKA) by computer-assisted navigation for primary medial osteoarthrosis with varus knee alignment. The hip-knee-ankle (HKA) angle, medial proximal tibial angle (MPTA), lateral distal femoral angle (LDFA), and joint line convergence angle (JLCA) were measured on which radiographs preoperatively. The radiographic parameters were compared between groups with HKA angle varus ≥ 10° and < 10°.

RESULTS

The MPTA was significantly lower (4°) in the HKA angle varus ≥ 10° group than in the < 10° group (82.13° vs. 86.13° P = 0.001), but the LDFA did not differ significantly between the groups (89.81° vs. 89.19° P = 0.181). Regarding the JLCA, the varus ≥ 10° group showed a 1.3° greater lateral widening than the varus < 10° group (4.87 vs. 3.56, P = 0.002). The MPTA was the only independent predictor of the MA of the lower limb (β =  -  0.353, P < 0.001).

CONCLUSION

One-third of varus osteoarthritic knees had a distal femur valgus phenotype. Varus knee alignment was mainly affected by proximal tibia varus rather than by distal femur varus.

LEVEL OF EVIDENCE

Level III, consecutive case series.

Patients with knee osteoarthritis can be divided into subgroups based on tibiofemoral joint kinematics of gait - an exploratory and dynamic radiostereometric study

OBJECTIVE

Patients with advanced knee osteoarthritis (KOA) frequently alter their gait patterns in an attempt to alleviate symptoms. Understanding the underlying pathomechanics and identifying KOA phenotypes are essential to improve treatments. We investigated kinematics in patients with KOA to identify subgroups of homogeneous knee joint kinematics.

METHOD

A total of 66 patients with symptomatic KOA scheduled for total knee arthroplasty and 15 age-matched healthy volunteers with asymptomatic, non-arthritic knees were included. We used k-means clustering to divide patients into subgroups based on dynamic radiostereometry-assessed tibiofemoral joint kinematics. Clinical characteristics such as knee ligament lesions and KOA scores were graded by magnetic resonance imaging and radiographs, respectively.

RESULTS

We identified four clusters that were supported by clinical characteristics. The flexion group (n = 20) consisted primarily of patients with medial KOA. The abduction group (n = 17) consisted primarily of patients with lateral KOA. The anterior draw group (n = 10) was composed of patients with medial KOA, some degree of anterior cruciate ligament lesion and the highest KOA score. The external rotation group (n = 19) primarily included patients with medial collateral and posterior cruciate ligament lesions.

CONCLUSION

Based on tibiofemoral gait patterns, patients with advanced KOA can be divided into four subgroups with specific clinical characteristics and different KOA-affected compartments. The findings add to our understanding of how knee kinematics may affect the patient's development of different types of KOA. This may inspire improved and more patient-specific treatment strategies in the future.

Axial alignment is a critical regulator of knee osteoarthritis

Although osteoarthritis (OA), a leading cause of disability, has been associated with joint malalignment, scientific translational evidence for this link is lacking. In a clinical case study, we provide evidence of osteochondral recovery upon unloading symptomatic isolated medial tibiofemoral knee OA associated with varus malalignment. By mapping response correlations at high resolution, we identify spatially complex degenerative changes in cartilage after overloading in a clinically relevant ovine model. We further report that unloading diminishes OA cartilage degeneration and alterations of critical parameters of the subchondral bone plate in a similar topographic fashion. Last, therapeutic unloading shifted the articular cartilage and subchondral bone phenotype to normal and restored several physiological correlations disturbed in neutral and varus OA, suggesting a protective effect on the integrity of the entire osteochondral unit. Collectively, these findings identify modifiable trajectories with considerable translational potential to reduce the burden of human OA.

Different Deformity Origins and Morphological Features in Subtypes of Valgus Knees: A Radiological Classification System

OBJECTIVE

To analyze the deformity origins and distribution among valgus knees to individualize their morphological features.

METHODS

Radiographic images of 105 valgus knees were analyzed. Long-film radiographs and computed tomography were collected for every knee. A malalignment test was performed on standing long-film radiographs. The hip-knee-ankle angle (HKA), the anatomical lateral distal femoral angle (aLDFA), and the anatomical medial proximal tibial angle (aMPTA) were measured on long-film radiographs. The distal condylar angle and posterior condylar angle on distal femur were further measured on computed tomography scans. The tibial bone varus angle was measured on long-film radiographs as well. All the valgus knees were sorted into different subtypes according to the origins of bony deformity, and the prevalence of each subtype was reported. Finally, to examine the inter-observer reproducibility of this classification system, two observers measured the deformities and did the classification for all the 105 knees independently and then the intraclass correlation coefficient (ICC) was calculated.

RESULTS

Among the 105 knees, 48 knees (45.7%) had apparent deformity from the tibial plateau, and 62 knees (59.0%) had apparent deformity from the supracondylar region of the femur. Eighteen knees (17.1%) had distal condylar angle >7°, among which 11 knees had posterior condylar angle >3° simultaneously. Valgus knees had five subtypes of bone deformity origins-the supracondylar part of the femur, the distal aspect of the lateral femoral condyle, both distal and posterior aspects of the lateral femoral condyle, the tibial plateau, or the metaphyseal segment of the tibia. A valgus knee could be labeled as only one subtype, or a combination of two or more subtypes. Labeling 105 knees with origin of the most severe deformity, the prevalence of each subtype was 40.0%, 5.7%, 9.5%, 28.6%, and 16.2%, respectively. The intra-observer and inter-observer ICC of this classification system was 0.992 and 0.976, respectively.

CONCLUSIONS

Valgus knees can be classified into different subtypes according to deformity origins. This radiological classification system has satisfactory reproducibility. It helps surgeons better individualize morphological features of valgus knees.

Tibial cartilage, subchondral bone plate and trabecular bone microarchitecture in varus- and valgus-osteoarthritis versus controls

This preliminary study quantified tibia cartilage thickness (Cart.Th), subchondral bone plate thickness (SBPl.Th) and subchondral trabecular bone (STB) microarchitecture in subjects with varus- or valgus- malaligned knees diagnosed with end-stage knee osteoarthritis (OA) and compared them to controls (non-OA). Tibial plateaus from 25 subjects with knee-OA (undergoing knee arthroplasty) and 15 cadavers (controls) were micro-CT scanned (17 µm/voxel). Joint alignment was classified radiographically for OA subjects (varus-aligned n = 18, valgus-aligned n = 7). Cart.Th, SBPl.Th, STB bone volume fraction (BV/TV) and their medial-to-lateral ratios were analyzed in anteromedial, anterolateral, posteromedial and posterolateral subregions. Varus-OA and valgus-OA were compared to controls. Compared to controls (1.19-1.54 mm), Cart.Th in varus-OA was significantly lower anteromedially (0.58 mm, -59%) and higher laterally (2.19-2.47 mm, +60-63%); in valgus-OA, Cart.Th was significantly higher posteromedially (1.86 mm, +56%). Control medial-to-lateral Cart.Th ratios were around unity (0.8-1.1), in varus-OA significantly below (0.2-0.6) and in valgus-OA slightly above (1.0-1.3) controls. SBPl.Th and BV/TV were significantly higher medially in varus-OA (0.58-0.72 mm and 37-44%, respectively) and laterally in valgus-OA (0.60-0.61 mm and 32-37%), compared to controls (0.26-0.47 mm and 18-37%). In varus-OA, the medial-to-lateral SBPl.Th and BV/TV ratios were above unity (1.4-2.4) and controls (0.8-2.1); in valgus-OA they were closer to unity (0.8-1.1) and below controls. Varus- and valgus-OA tibia differ significantly from controls in Cart.Th, SBPl.Th and STB microarchitecture depending on joint alignment, suggesting structural changes in OA may reflect differences in medial-to-lateral load distribution upon the tibial plateau. Here we identified an inverse relationship between cartilage thickness and underlying subchondral bone, suggesting a whole-joint response in OA to daily stimuli.

Analysis of spatial osteochondral heterogeneity in advanced knee osteoarthritis exposes influence of joint alignment

Osteoarthritis (OA) is considerably affected by joint alignment. Here, we investigate the patterns of spatial osteochondral heterogeneity in patients with advanced varus knee OA together with clinical data. We report strong correlations of osteochondral parameters within individual topographical patterns, highlighting their fundamental and location-dependent interactions in OA. We further identify site-specific effects of varus malalignment on the lesser loaded compartment and, conversely, an unresponsive overloaded compartment. Last, we trace compensatory mechanisms to the overloaded subarticular spongiosa in patients with additional high body weight. We therefore propose to consider and to determine axial alignment in clinical trials when selecting the location to assess structural changes in OA. Together, these findings broaden the scientific basis of therapeutic load redistribution and weight loss in varus knee OA.

Expression and Localization of Thrombospondins, Plastin 3, and STIM1 in Different Cartilage Compartments of the Osteoarthritic Varus Knee

Osteoarthritis (OA) is a multifactorial disease which is characterized by a change in the homeostasis of the extracellular matrix (ECM). The ECM is essential for the function of the articular cartilage and plays an important role in cartilage mechanotransduction. To provide a better understanding of the interaction between the ECM and the actin cytoskeleton, we investigated the localization and expression of the Ca²⁺-dependent proteins cartilage oligomeric matrix protein (COMP), thrombospondin-1 (TSP-1), plastin 3 (PLS3) and stromal interaction molecule 1 (STIM1). We investigated 16 patients who suffered from varus knee OA and performed a topographical analysis of the cartilage from the medial and lateral compartment of the proximal tibial plateau. In a varus knee, OA is more pronounced in the medial compared to the lateral compartment as a result of an overloading due to the malalignment. We detected a location-dependent staining of PLS3 and STIM1 in the articular cartilage tissue. The staining intensity for both proteins correlated with the degree of cartilage degeneration. The staining intensity of TSP-1 was clearly reduced in the cartilage of the more affected medial compartment, an observation that was confirmed in cartilage extracts by immunoblotting. The total amount of COMP was unchanged; however, slight changes were detected in the localization of the protein. Our results provide novel information on alterations in OA cartilage suggesting that Ca²⁺-dependent mechanotransduction between the ECM and the actin cytoskeleton might play an essential role in the pathomechanism of OA.

Setting up distinctive outcome measures for each osteoarthritis phenotype

Osteoarthritis (OA) is an evolving chronic joint disease with a huge global impact. Given the intricate nature of the etiopathogenesis and subsequent high heterogeneity in the clinical course of OA, it is crucial to discriminate between etiopathogenic endotypes and clinical phenotypes, especially in the early stages of the disease. In this sense, we propose that an OA phenotype should be properly assessed with a set of outcome measures including those specifically related to the main underlying pathophysiological mechanisms. Thus, each OA phenotype can be related to different and clinically meaningful outcomes. OA phenotyping would lead to an adequate patient stratification in well-designed clinical trials and the discovery of precise therapeutic approaches. A significant effort will be required in this field in light of inconclusive results of clinical trials of tissue-targeting agents for the treatment of OA.

The influence of femoral and tibial bony anatomy on valgus OA of the knee

PURPOSE

Approximately 10% of all patients that require a total knee arthroplasty present with valgus osteoarthritis (OA) of the knee. Valgus OA goes along with posterolateral bone loss and lateral soft tissue tightness. The role of malalignment on the development of OA is not fully understood. The current study investigates whether the femoral offset (FO), femoral mechanical-anatomical (FMA) angle, anatomical lateral distal femur angle (aLDFA), mechanical lateral distal femur angle (mLDFA), medial proximal femur angle (MPFA), medial proximal tibia angle (MPTA) or lateral distal tibia angle (LDTA) differ in patients with valgus OA of the knee.

METHODS

FO, FMA angle, aLDFA, mLDFA, MPFA, MPTA and LDTA were assessed and compared between 100 consecutive knees with minimal valgus OA (50 male, 50 female) and 100 consecutive knees with minimal varus OA (50 male, 50 female).

RESULTS

FO was significantly higher in males with valgus OA (p = 0.002) and females with varus OA (p = 0.01). The observed values for the FMA angle were significantly higher in males with valgus OA (p = 0.002) and females with varus OA (p = 0.041). The aLDFA and mLDFA were significantly smaller in all patients with valgus OA (p < 0.001). No differences between the varus and valgus groups were detected regarding MPFA (males: p = 0.052; females: p = 0.719). Tibial measurements showed significantly higher values for the MPTA (p < 0.001) in both valgus groups and no difference for LDTA (men: p = 0.139; women: p = 0.196).

CONCLUSION

Bony alterations in the femoral anatomy seem to be more important than in the tibial anatomy. While in male patients with valgus OA, the main anatomic variation is the hypoplasia of the lateral femoral condyle, in females both decreased femoral offset of the hip as well as hypoplasia of the lateral condyle are present.

LEVEL OF EVIDENCE

III.

Cartilage survival of the knee strongly depends on malalignment: a survival analysis from the Osteoarthritis Initiative (OAI)

PURPOSE

Progression of osteoarthritis over time is poorly understood. The aim of the current study was to establish a timeline of "cartilage survival rate" per subregion of the knee in relation to mechanical alignment of the lower extremity. The study hypothesized that there are differences in progression of osteoarthritis between varus, valgus and physiologic lower extremity alignment.

METHODS

Based on hip-knee-ankle standing radiographs at baseline, 234 knees had physiologic (180° ± 3°, mean 179.7°), 158 knees had varus (< 177°; mean 174.5°) and 66 knees valgus (> 183°; mean 185.2°) alignment (consecutive knees of the OAI "Index Knee" group, n = 458; mean age 61.7; 264 females). The Osteoarthritis Initiative (OAI; a multi-center, longitudinal, prospective observational study of knee osteoarthritis [30] using MRIs) defines progressive OA as a mean decrease of cartilage thickness of 136 µm/year and a mean decrease of cartilage volume by 5% over 1 year (DESS sequences, MRI). A Kaplan-Meier curve was generated for osteoarthritis progression based on OAI criteria.

RESULTS

Osteoarthritis progression based on volume decrease of 5% in varus knees occurred after 30.8 months (medial femoral condyle), after 37 months (medial tibia), after 42.9 months (lateral femoral condyle) and 43.4 months (lateral tibia), respectively. In a valgus alignment progression was detectable after 31.5 months (lateral tibia), after 36.2 months (lateral femoral condyle), after 40.4 months (medial femoral condyle) and 43.8 months (medial tibia), respectively. The physiological alignment shows a progression after 37.8 months (medial femoral condyle), after 41.6 months (lateral tibia), after 41.7 months (medial tibia) and after 43 months (lateral femoral condyle), respectively.

CONCLUSION

Based on data from the OAI, the rate and location (subregion) of osteoarthritis progression of the knee is strongly associated with lower extremity mechanical alignment.

LEVEL OF EVIDENCE

Level I (prognostic study).

Changes in Medial Meniscal Three-Dimensional Position and Morphology As Predictors of Knee Replacement in Rapidly Progressing Knee Osteoarthritis: Data From the Osteoarthritis Initiative

OBJECTIVE

To assess whether quantitative changes in the meniscus predict progression from early knee osteoarthritis (OA) to knee replacement (KR).

METHODS

A nested case-control study was conducted among Osteoarthritis Initiative participants: all 35 case knees with baseline Kellgren/Lawrence (K/L) grade ≤2 that had KR between 36 and 60 months were matched 1:1 by age, sex, and baseline K/L grade to 35 control knees without subsequent KR. Quantitative 3-dimensional medial meniscus position and morphologic measures were determined from magnetic resonance imaging at the visit just before KR and 2 years before. Paired t-tests and case-control odds ratios (ORs, standardized per SD of change in controls) were used to compare changes between groups.

RESULTS

Cases (52% women, age 65 ± 7 years, body mass index [BMI] 30 ± 4 kg/m² , K/L grades 0/1/2: 5/8/22 participants, respectively) and controls (52% women, age 64 ± 7 years, BMI 30 ± 5 kg/m² , K/L grades 0/1/2: 9/4/22 participants, respectively) were similar. Compared to control knees, KR case knees displayed longitudinal changes, specifically, a decrease in tibial plateau coverage, an increase in meniscal extrusion, and a decrease in meniscal width. The odds for KR increased with greater reduction in the percentage of tibial plateau coverage (OR 2.28 [95% CI confidence interval (95% CI) 1.43, 3.64]), a greater increase in maximal extrusion (OR 1.40 [95% CI 1.12, 1.75]), and a greater reduction of mean meniscal width (OR 2.01 [95% CI 1.23, 3.26]). The odds for KR increased with medial compartment cartilage thickness loss (OR 2.86 [95% CI 1.51, 5.41]) for comparison.

CONCLUSION

Quantitative measures of meniscal position and morphology are associated with subsequent KR in knees with rapidly progressing knee OA. These findings show that structural changes of the meniscus are related to an important clinical and economic outcome of knee OA.

The Transverse Infrapatellar View: A New Ultrasound Technique to Measure Distal Femoral Cartilage Thickness

OBJECTIVES

To examine the reliability and face validity of ultrasound (US) measurements of distal femoral cartilage thickness (CT) using the infrapatellar view (IPV) with knee extension compared to the traditional suprapatellar view (SPV) with knee hyperflexion in young asymptomatic participants and patients with painful knee osteoarthritis (KOA).

METHODS

The IPV was obtained in an extended knee position by placing the US transducer on the patellar tendon at a 60° angle tilted toward the distal femoral condyle in 19 young adults (control group) and 70 patients with KOA. The CT was measured at the medial femoral condyle, the intercondylar notch, and the lateral femoral condyle.

RESULTS

The inter-rater intraclass correlation coefficient was higher for IPV-based CT measurement (range, 0.856-0.858) compared to SPV-based CT measurement (range, 0.315-0.523) among the patients with symptomatic KOA. The IPV-based CT differed significantly between the control group and the KOA group at the intercondylar notch (P < .001) and lateral femoral condyle (P = .006). The SPV-based CT differed significantly between the control group and the KOA group only at the lateral femoral condyle region (P = .014).

CONCLUSIONS

An infrapatellar US evaluation of the distal femoral CT can be a reliable alternative method to a suprapatellar US evaluation for patients with KOA.

Association of age, sex and BMI with the rate of change in tibial cartilage volume: a 10.7-year longitudinal cohort study

Background

To describe the association of age, sex and body mass index with the rate of change of tibial knee cartilage volume over 10.7 years in a community-based sample of older adults.

Methods

Four hundred and eighty-one participants (49% female, mean age 60.8 years [range 51.1–79.7], 49% had knee pain and 58% radiographic osteoarthritis) were included. Tibial cartilage volume of the right knee was assessed on T1-weighted fat-suppressed 1.5 T MRI at baseline and 10.7 years. Data analyses were performed using linear regression models.

Results

The average rate of loss of cartilage volume was 1.2%/year (range 0.2–3.9%) with all participants losing cartilage volume over the study period. There was a significant association between age and loss of tibial cartilage volume in the medial (0.023%/year, 95% confidence interval [CI] 0.010 to 0.036%, p < 0.001), lateral (0.013%/year, 95% CI 0.003 to 0.023%, p = 0.012) and total tibia (0.018%/year, 95% CI 0.009 to 0.026%, p < 0.001). Higher body mass index at baseline and increases in body mass index over time were associated with a greater tibial cartilage loss at the medial (body mass index at baseline 0.040%/year, 95% CI 0.022 to 0.058%, p < 0.001; increases in body mass index 0.055%/year, 95% CI 0.018 to 0.093%, p = 0.004) but not lateral compartment. No evidence of non-linear relationships was observed. Compared to males, females lost more lateral tibial cartilage with increasing age (0.023%/year, 95% CI 0.003 to 0.043%, p = 0.024 for interaction).

Conclusions

Tibial cartilage volume declines at a faster rate with increasing age and body mass index in both males and females, particularly in the medial compartment. In contrast to the low rate of change in radiographs, our findings suggest that cartilage loss at the tibia is universal in this age group.

Validation of a novel blinding method for measuring postoperative knee articular cartilage using magnetic resonance imaging

OBJECTIVES

To test PEEK implant-associated MRI artifacts, a method for blinding MRI readers, the repeatability of cartilage thickness measures before and 6 weeks after high tibial osteotomy (HTO), and the sensitivity to change of cartilage thickness 12 months after HTO.

MATERIALS AND METHODS

Ten patients underwent HTO using a PEEK implant and 3 T-MRI before, 6 weeks and 12 months after surgery. Masks were applied to hide implant visibility on 48 MRI pairs, which were assessed by 7 readers (blinded to time). One blinded reader measured femorotibial cartilage thickness from masked MRIs.

RESULTS

No artifacts were produced. Readers were unable to identify scans by time greater than by chance. Cartilage thickness before and 6 weeks after surgery was not significantly different and indicated excellent repeatability. Medial cartilage thickness increases 12 M postoperatively approached statistical significance (p = 0.06), with no lateral changes observed. Half of the participants had an increase in medial cartilage thickness at 12 M that exceeded the minimal detectable change. Standardized response mean values were moderate-to-large.

DISCUSSION

Postoperative measures of cartilage thickness are repeatable, consistent and sensitive to change when artifact is eliminated, and a validated blinding technique is used. These results provide proof of concept for accurately measuring increases in medial knee articular cartilage after medial opening wedge HTO.

Relationship between knee alignment in asymptomatic subjects and flexibility of the main muscles that are functionally related to the knee

Objective To assess the relationship between static frontal knee alignment in asymptomatic subjects and flexibility of the main muscles functionally related to the knee. Methods A descriptive cross-sectional study was performed in 33 healthy adults (19-31 years). The frontal knee angle (valgus/varus angle) was measured by photogrammetry and it was measured in the lateral side. Therefore, high values were assigned for genu varum and low values for genu valgum. Iliopsoas, gluteus maximus and medius, rectus femoris, biceps femoris, vastus of the quadriceps, and gastrocnemius muscles were stretched. Muscles were classified as normal, reflex hypomobile, or structural hypomobile. Results Women had significantly greater valgus than did men (right angle, women: 174.41°/men: 177.41°; left angle, women: 174.20°/men: 178.70°). The right frontal plane knee angle was higher in women with structural hypomobile vastus. The left frontal plane knee angle was higher in women with structural hypomobile iliopsoas. No relationships were found in men. Conclusions A tighter vastus of the quadriceps and tighter iliopsoas are related to greater genu varum in adult women. Stretching the vastus of the quadriceps and iliopsoas when there is a tendency for excess varus in the knee, to prevent overuse injury or early osteoarthritis, might be clinically relevant.

Prophylaxis of medial compartment gonarthrosis in varus knee - current state of knowledge

The progression of gonarthrosis results in reduction of physical activity. One of the factors that increase the risk of osteoarthrosis may be joint overload related to the malalignment of the mechanical axis of the lower extremity. The medial compartment (MC) of the knee is particularly susceptible to overload due to the external knee adduction moment (EKAM). Varus knee malalignment contributes to increased EKAM and thus results in increased MC loading. The purpose of this study is to present methods described in current literature aimed at reducing the disproportion in the distribution of loads on articular surfaces of medial and lateral knee compartments in people with varus knee malalignment. Methods have been divided into non-surgical (gait training, physiotherapy, and orthopedic supplies such as valgus braces, lateral wedge insoles, walking poles) and surgical ones (corrective osteotomy).

Knee internal contact force in a varus malaligned phenotype in knee osteoarthritis (KOA)

PURPOSE

Multiple phenotypes characterized by different disease mechanisms have been hypothesized to explain the large variability in the knee osteoarthritis (KOA) population. The purpose of this study was: to estimate and compare the medial and lateral knee compression forces (CF) during gait of three subgroups of KOA subjects characterized by different alignment and cartilage disruption patterns.

METHODS

A secondary data analysis was conducted on a sample of 39 KOA subjects and 18 controls (C). The patients were classified in the different groups according to the following criteria: Varus medial disease (VMD) (12): varus alignment and predominant medial cartilage degeneration Varus generalized disease (VGD) (17): varus alignment and cartilage degeneration that extends to the lateral compartment. Neutral alignment (NA) (10): neutral alignment. The total, medial and lateral CF corrected for body weight were estimated using an inverse dynamics model (AnyBody Modeling System, AnyBody Technology) during stance.

RESULTS

The impulse of the medial compressive force (MCF) (overall effect of the CF over the stance) was significantly higher (P < 0.01) in the VMD compared to all the other groups. Peak MCF was higher in the VMD compared to all the other groups, but the difference reached significance only when compared to the VGD group (P < 0.05). The results of the regression analysis showed a significant relationship in the VMD group between alignment and impulse of the MCF (R² = 0.62; P < 0.01). This relationship disappears in the other groups.

CONCLUSIONS

These findings suggest the existence of a phenotype characterized by increased MCF.

Mediolateral force distribution at the knee joint shifts across activities and is driven by tibiofemoral alignment

AIMS

Tibiofemoral alignment is important to determine the rate of progression of osteoarthritis and implant survival after total knee arthroplasty (TKA). Normally, surgeons aim for neutral tibiofemoral alignment following TKA, but this has been questioned in recent years. The aim of this study was to evaluate whether varus or valgus alignment indeed leads to increased medial or lateral tibiofemoral forces during static and dynamic weight-bearing activities.

PATIENTS AND METHODS

Tibiofemoral contact forces and moments were measured in nine patients with instrumented knee implants. Medial force ratios were analysed during nine daily activities, including activities with single-limb support (e.g. walking) and double-limb support (e.g. knee bend). Hip-knee-ankle angles in the frontal plane were analysed using full-leg coronal radiographs.

RESULTS

The medial force ratio strongly correlated with the tibiofemoral alignment in the static condition of one-legged stance (R² = 0.88) and dynamic single-limb loading (R² = 0.59) with varus malalignment leading to increased medial force ratios of up to 88%. In contrast, the correlation between leg alignment and magnitude of medial compartment force was much less pronounced. A lateral shift of force occurred during activities with double-limb support and higher knee flexion angles.

CONCLUSION

The medial force ratio depends on both the tibiofemoral alignment and the nature of the activity involved. It cannot be generalised to a single value. Higher medial ratios during single-limb loading are associated with varus malalignment in TKA. The current trend towards a 'constitutional varus' after joint replacement, in terms of overall tibiofemoral alignment, should be considered carefully with respect to the increased medial force ratio. Cite this article: Bone Joint J 2017;99-B:779-87.

Three-dimensional analysis of the tibial resection plane relative to the arthritic tibial plateau in total knee arthroplasty

Background

Kinematically aligned total knee arthroplasty strives to correct the arthritic deformity by restoring the native tibial joint line. However, the precision of such surgical correction needs to be quantified in order to reduce recuts of the resection and to design assisting instrumentation. This study describes a method for novel three-dimensional analysis of tibial resection parameters in total knee arthroplasty. Pre-operative versus post-operative differences in the slopes of the varus-valgus and flexion-extension planes and the proximal-distal level between the tibia resection and the arthritic tibial joint line can reliably be measured using the three-dimensional models of the tibia and fibula. This work uses the proposed comparison method to determine the parameters for resecting the tibia in kinematically aligned total knee arthroplasty.

Methods

Three-dimensional shape registration was performed between arthritic surface models segmented from pre-operative magnetic resonance imaging scans and resected surface models segmented from post-operative computed tomography scans. Mean, standard deviation and 95% confidence intervals were determined for all measurements. 

Results

Results indicate that kinematically aligned total knee arthroplasty consistently corrects the varus deformity and restores the slope of the flexion-extension plane and the proximal-distal level of the arthritic tibial joint line. The slope of the varus-valgus plane is most precisely associated with the overall arthritic slope after approximately 3° of correction and the posterior slope is biased towards the overall arthritic plateau, though less precisely than the varus correlation.

Conclusions

Use of this analysis on a larger population can quantify the effectiveness of the tibial resection for correcting pathologies, potentially reduce imprecisions in the surgical technique, and enable development of instrumentation that reduces the risk of resection recuts. The kinematic alignment technique consistently corrects varus deformities.

Matrix Production Affects MRI Outcomes After Matrix-Associated Autologous Chondrocyte Transplantation in the Knee

BACKGROUND

Matrix-associated autologous chondrocyte transplantation (MACT) has been an effective therapy for large, full-thickness cartilage lesions for years. However, little is known about how graft maturation is affected by characteristics of transplanted chondrocytes.

PURPOSE

To investigate the influence of gene expression of chondrocytes at the time of transplantation on MRI outcomes up to 2 years after MACT.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

This study included 25 patients with 27 symptomatic traumatic defects of articular cartilage, who had undergone MACT in the knee. Postoperative MRI examinations were conducted at 3, 6, 12, and 24 months after surgery. Biochemical graft maturation was assessed by measuring T2 relaxation time values of the transplant and healthy native cartilage areas. The MOCART (magnetic resonance observation of cartilage repair tissue) score was used to evaluate the morphological quality of regeneration tissue. Gene expression (collagen type I, collagen type II, aggrecan, versican, and interleukin-1β) was determined by real-time polymerase chain reaction (PCR) in transplant residuals at the time point of transplantation and was correlated with MRI outcomes using Spearman's rank correlation coefficient. A Friedman test with post hoc analysis (Wilcoxon signed rank test) conducted with a Bonferroni correction was applied to compare scores at different time points.

RESULTS

T2 relaxation time of regeneration tissue improved from a mean ± SD of 74.6 ± 20.1 milliseconds at 3 months to 47.9 ±13.3 milliseconds at 24 months ( P < .003). These values were similar to the T2 relaxation times of the native surrounding cartilage (50.9 ± 15 ms). The calculated T2 index (ratio of regeneration tissue to native cartilage) improved from 1.63 ± 0.76 at 3 months to 1.0 ± 0.4 at 24 months ( P < .011). The MOCART score increased from 51.6 ± 15 points to 72.4 ± 12.2 points ( P < .001). Improvement of the T2 index over time significantly correlated with aggrecan, COL1A1, COL2A1, and versican expression ( r_s = 0.9, P < .001; r_s = 0.674, P < .012; r_s = 0.553, P < .05; and r_s = 0.575, P < .04, respectively). No correlation was found for IL-1β.

CONCLUSION

These data demonstrate that matrix production in transplanted chondrocytes affects maturation of MACT grafts in MRI 2 years after surgery.

Longitudinal Changes in Magnetic Resonance Imaging-Based Measures of Femorotibial Cartilage Thickness as a Function of Alignment and Obesity: Data From the Osteoarthritis Initiative

OBJECTIVE

To investigate the interaction between malalignment and body mass index (BMI) on cartilage thickness change in patients with knee osteoarthritis (OA).

METHODS

Femorotibial cartilage thickness was measured from baseline to 2 years in 558 knees with radiographic OA. Cartilage thickness was determined in the central weight-bearing medial femorotibial cartilage (cMFTC) and lateral (cLFTC) compartments. Femorotibial angle (FTA) was stratified into neutral, minor, and definite malalignment. BMI was stratified using World Health Organization classifications for normal, overweight, and obese. Multivariable linear regression models were used to investigate the interaction between alignment and BMI, adjusting for age, sex, and disease severity.

RESULTS

There was no significant interaction for continuous measures of alignment and BMI (P = 0.301 for cMFTC and P = 0.852 for cLFTC). Using BMI tertiles, the association between alignment and medial or lateral cartilage thickness loss was not moderated by BMI, despite a significant association of malalignment with greater cartilage thickness loss (P ≤ 0.005). Using FTA tertiles, the association between BMI and medial cartilage thickness loss was approximately 3 times greater in knees with definite malalignment (P = 0.149) and approximately 5 times greater in knees with minor malalignment (P = 0.006). Specifically, knees with minor varus significantly modified this relationship (P = 0.021).

CONCLUSION

Malalignment was significantly associated with cartilage thickness loss per degree increase in malalignment, but was not moderated by BMI. BMI was significantly associated with greater rates of medial cartilage thickness loss per unit increase in BMI but only in knees with minor varus malalignment. These findings have implications for better understanding patient subgroups and intervention strategies targeting risk factors for knee OA.

Design of Reverse Materials Resurfacing Implants for Mild–Moderate Medial Osteoarthritis of the Knee

The areas of the most frequent cartilage loss in mild–moderate medial osteoarthritis (OA) were reviewed from previous studies. Implant components were designed to resurface these areas. The surface geometries of the components were based on an average femur and tibia produced from 20 magnetic resonance imaging (MRI) models of normal knees. Accuracy of fit of the components was determined on these 20 individual knees. The femoral surface was toroidal, covering a band on the distal end of the femur, angled inward anteriorly. For a five-size system, the average deviations between the implant surfaces and the intact cartilage surfaces of 20 femurs were only 0.3 mm. For the tibia, the deviations were 0.5–0.7 mm, but the errors were mainly around the tibial spine, with smaller deviations in the central bearing region. Hence, these small implant components would accurately restore the original bearing surfaces and allow for preservation of all the knee structures. Using a thin metal component for the tibia would preserve the strong cancellous bone near the surface, an advantage for fixation. In this case, the femoral component would have a plastic bearing surface, but still be less than 10 mm thickness. Such a design could have a useful place in the early treatment of medial OA of the knee.

Diagnosis and Longitudinal Assessment of Osteoarthritis: Review of Available Imaging Techniques

Osteoarthritis (OA) is a major chronic and global health care problem. Recent technological advances in imaging and postprocessing techniques have enhanced the understanding and characterization of the pathophysiology of this chronic and prevalent disease. Although plain radiograph remains the modality of choice for initial assessment of OA, recent studies have shown that advanced cross-sectional imaging can improve the early detection, grading, structural damage quantification, and risk stratification of OA. This article discusses the currently available evidence regarding both the conventional and novel imaging modalities that can be used for evaluation of patients with OA and its longitudinal assessment.

Differences in subchondral bone size after one year in osteoarthritic and healthy knees

OBJECTIVE

Increase of subchondral bone area (tAB) in OA has been reported, but it remains unclear if this is specific to OA. We investigated differences in knee tAB after one year in healthy subjects and in those with radiographic OA (rOA).

METHOD

MR images of 899 right knees from the OA Initiative were acquired at baseline and one year follow-up (year-1). Medial and lateral tibial cartilage (MT and LT) and weight-bearing femoral cartilage (cMF and cLF) were segmented and tAB computed. Subjects were stratified into: healthy controls, pre-rOA (K&L grades 0 and 1, with OA risk factors), established rOA (K&L grades 2-4), and independently with regards to joint space narrowing (without, with medial, lateral and bilateral JSN). Primary analysis tested if tAB was different between baseline and year-1 in rOA. Exploratory analyses investigated whether: (1) tAB changes differed between healthy controls and those with rOA; (2) tAB differences were greater in higher K&L grades; and (3) tAB was different between baseline and year-1 in JSN. Significance was set at P < 0.0125.

RESULTS

Differences in tAB were found in rOA in MT, cMF and cLF (ranging from +0.2% to +0.4%; P < 0.001), but not in healthy controls or pre-rOA. Rates of change did not differ between groups. Within the JSN groups differences of 0.2-0.4% were found in the femur (P < 0.05).

CONCLUSION

We find that knee tABs differ in rOA between baseline and year-1, but the change was not greater than in healthy knees, and is restricted to the femur in JSN.

Anatomical alignment, but not goniometry, predicts femorotibial cartilage loss as well as mechanical alignment: data from the Osteoarthritis Initiative

OBJECTIVE

To determine how frontal plane lower limb alignment obtained using a new femorotibial angle (FTA) measurement and non-radiographic handheld goniometry, predict femorotibial cartilage thickness loss in varus and valgus knees, compared with the gold standard mechanical axis (hip-knee-ankle [HKA]).

METHODS

934 Osteoarthritis (OA) Initiative knees with radiographic OA had the above alignment measures and 3T knee MRIs acquired. The new FTA measure was compared to the gold standard, with and without adjusting FTA for the sex-specific varus shift. Changes in medial (MFTC) and lateral femorotibial (LFTC) cartilage thickness were quantified over 1-year and 2-years. Adjusted odds ratios (adjORs) were used to compare how the different alignment measures predict medial and lateral cartilage loss in varus and valgus knees.

RESULTS

Pearson correlation coefficients between 2-year MFTC/LFTC cartilage loss and alignment measures were small to moderate, and were similar for FTA (r = 0.28/-0.30) and for HKA (r = 0.28/-0.29). Using the adjusted FTA measure, varus and valgus predicted MFTC progression (adjOR = 3.73) and LFTC progression (adjOR = 2.55) as well as HKA (adjOR = 3.16 and 2.31) over 1-year, and this relationship was also observed over 2-years. Goniometry was a weak predictor for MFTC and LFTC progression (adjOR1-year = 1.65 and 1.71; adjOR2-year = 0.68 and 1.24).

CONCLUSIONS

After adjustment, the new FTA measure obtained from short (fixed-flexion) knee films was as good as the gold standard in predicting medial and lateral cartilage loss over 1- or 2-years, without need for obtaining long-limb radiographs for determining the mechanical axis. Goniometry and non-adjusted FTA measures, in contrast, were poor predictors of cartilage loss.

Three-dimensional hip and knee kinematics during walking, running, and single-limb drop landing in females with and without genu valgum

BACKGROUND

Dynamic knee valgus in females has been associated with various knee pathologies. Abnormal 3D hip and knee kinematics contribute prominently to this presentation, and these may become more aberrant with more demanding tasks. Underlying genu valgus may also accentuate such kinematics, but this effect has never been tested. Therefore, the purpose of this study was to compare 3D hip and knee kinematics during walking, running, and single-limb drop landing in females with and without genu valgus malalignment. We expected abnormal kinematics to become more evident in the valgus subjects as task demands increased.

METHODS

Eighteen healthy females with genu valgum and 18 female controls with normal alignment underwent 3D motion analysis while performing walking, running, and single-limb drop-landing trials. Sagittal, frontal, and transverse plane hip and knee kinematics were compared between groups across tasks using analyses of variance and between-group effect sizes.

FINDINGS

Group differences did not generally increase with higher forces. The valgus females demonstrated decreased hip flexion (ES=0.72-0.88) and increased knee abduction (ES=0.87-1.47) across the tasks. During running and single-limb drop landing, they showed increased knee external rotation (ES=0.69-0.73). Finally, during walking, the valgus females showed increased hip adduction (ES=0.69).

INTERPRETATION

These results suggest that females with genu valgus alignment utilize aberrant hip and knee mechanics previously associated with dynamic valgus in the literature, but that these pathomechanics do not generally worsen with rising task demands. Healthy females that present with genu valgus may be natively at elevated risk for knee pathology.

Conventional and novel imaging modalities in osteoarthritis: current state of the evidence

PURPOSE OF REVIEW

Imaging modalities are currently an inseparable part of osteoarthritis diagnosis. In this review, we describe the current state of evidence regarding conventional and novel imaging modalities in evaluation of osteoarthritis. Modalities including radiography (qualitative and semi-quantitative assessments), ultrasonography, computed tomography [CT; conventional multidetector CT (MDCT), cone-beam CT (CBCT) and four-dimensional CT (4DCT)], MRI (MRI; semi-quantitative, quantitative and compositional) and PET and their applications are reviewed.

RECENT FINDINGS

Radiography is the modality of choice for initial assessment of osteoarthritis. However, due to its low sensitivity and specificity, numerous recent investigations have proposed MRI as a powerful addition to detect and grade osteoarthritis features, which are not apparent in radiography. Semi-quantitative MRI measurements are feasible to perform in routine clinical practice. Quantitative and compositional MRI measurements have extended the amount of information an MRI examination can provide regarding the three-dimensional shape and tissue composition of articular cartilage. 4DCT and CBCT are introduced as imaging examinations that may reveal biomechanical cartilage abnormalities in osteoarthritis joint by dynamic and weight-bearing evaluations, respectively. Recent PET studies may unveil the underlying metabolic activities that can be associated with osteoarthritis.

SUMMARY

In addition to the established role of radiographs, MRI is the advanced modality of choice for detection and quantification of various osteoarthritis features. 4DCT and CBCT may have specified applications when diagnosis of underlying motion abnormality or dynamic changes in weight-bearing situation is suspected. Future studies should elucidate the specific clinical applications of ultrasonography and PET.

Development of a Rapid Cartilage Damage Quantification Method for the Lateral Tibiofemoral Compartment Using Magnetic Resonance Images: Data from the Osteoarthritis Initiative

The purpose of this study was to expand and validate the cartilage damage index (CDI) to detect cartilage damage in the lateral tibiofemoral compartment. We used an iterative 3-step process to develop and validate the lateral CDI: development (100 knees), testing (80 knees), and validation (100 knees). The validation set included 100 knees from the Osteoarthritis Initiative that was enriched to include all grades of lateral joint space narrowing (JSN, 0–3). Measurement of the CDI was rapid at 7.4 (s.d. 0.73) minutes per knee pair (baseline and follow-up of one knee). The intratester reliability is good (intraclass correlation coefficient (3, 1 model) = 0.86 to 0.98). At baseline, knees with greater KL grade and lateral JSN had a lower mean CDI (i.e., greater cartilage damage). Baseline lateral CDI is associated with both lateral JSW (r = 0.81 to 0.85, p < 0.01) and HKA (r = −0.30 to −0.33, p < 0.05). The SRM is good (lateral femur SRM = −0.76; lateral tibia SRM = −0.73; lateral tibiofemoral total SRM = −0.87). The lateral tibiofemoral CDI quantification allows for rapid evaluation and is reliable and responsive, with good construct validity. It may be an efficient method to measure lateral tibiofemoral articular cartilage in large clinical and epidemiologic studies.

Is loss in femorotibial cartilage thickness related to severity of contra-lateral radiographic knee osteoarthritis?--longitudinal data from the Osteoarthritis Initiative

OBJECTIVE

Anti-catabolic disease modifying drugs (DMOADs) aim to reduce cartilage loss in knee osteoarthritis (KOA). Testing such drugs in clinical trials requires sufficient rates of loss in the study participants to occur, preferably at a mild disease stage where cartilage can be preserved. Here we analyze a "progression" model in mild radiographic KOA (RKOA), based on contra-lateral radiographic status.

METHODS

We studied 837 participants (62.4 ± 9 yrs; 30 ± 4.9 kg/m²; 61.8% women) from the Osteoarthritis Initiative (OAI) with mild to moderate RKOA (Kellgren Lawrence grade [KLG] 2-3) and with/without Osteoarthritis Research Society International (OARSI) atlas radiographic joint space narrowing (JSN). These had quantitative measurements of subregional femorotibial cartilage thickness from magnetic resonance imaging (MRI) at baseline and 1-year follow-up. They were stratified by contra-lateral knee status: no (KLG 0/1), definite (KLG2) and moderate RKOA (KLG 3/4).

RESULTS

KLG2 knees with JSN and moderate contra-lateral RKOA had (P = 0.008) greater maximum subregional cartilage loss -220 μm [95% confidence interval (CI) -255, -184 μm] than those without contra-lateral RKOA -164 μm [-187, -140 μm]. Their rate of subregional cartilage loss was similar and not significantly different (P = 0.61) to that in KLG 3 knees without contra-lateral RKOA (-232 μm; [-266; -198 μm]). The effect of contra-lateral RKOA status was less in KLG2 knees without JSN, and in KLG3 knees.

CONCLUSION

KLG2 knees with JSN and moderate contra-lateral RKOA, display relatively high rates of subregional femorotibial cartilage loss, despite being at a relatively mild stage of RKOA. They may therefore provide a unique opportunity for recruitment in clinical trials that explore the efficacy of anti-catabolic DMOADs on structural progression.

Imaging of cartilage and bone: promises and pitfalls in clinical trials of osteoarthritis

Imaging in clinical trials is used to evaluate subject eligibility, and/or efficacy of intervention, supporting decision making in drug development by ascertaining treatment effects on joint structure. This review focusses on imaging of bone and cartilage in clinical trials of (knee) osteoarthritis. We narratively review the full-text literature on imaging of bone and cartilage, adding primary experience in the implementation of imaging methods in clinical trials. Aims and constraints of applying imaging in clinical trials are outlined. The specific uses of semi-quantitative and quantitative imaging biomarkers of bone and cartilage in osteoarthritis trials are summarized, focusing on radiography and magnetic resonance imaging (MRI). Studies having compared both imaging methodologies directly and those having established a relationship between imaging biomarkers and clinical outcomes are highlighted. To make this review of practical use, recommendations are provided as to which imaging protocols are ideal for capturing specific aspects of bone and cartilage tissue, and pitfalls in their usage are highlighted. Further, the longitudinal sensitivity to change, of different imaging methods is reported for various patient strata. From these power calculations can be accomplished, provided the strength of the treatment effect is known. In conclusion, current imaging methodologies provide powerful tools for scoring and measuring morphological and compositional aspects of most articular tissues, capturing longitudinal change with reasonable to excellent sensitivity. When employed properly, imaging has tremendous potential for ascertaining treatment effects on various joint structures, potentially over shorter time scales than required for demonstrating effects on clinical outcomes.

Intraarticular sprifermin (recombinant human fibroblast growth factor 18) in knee osteoarthritis: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

To evaluate the efficacy and safety of intraarticular sprifermin (recombinant human fibroblast growth factor 18) in the treatment of symptomatic knee osteoarthritis (OA).

METHODS

The study was a randomized, double-blind, placebo-controlled, proof-of-concept trial. Intraarticular sprifermin was evaluated at doses of 10 μg, 30 μg, and 100 μg. The primary efficacy end point was change in central medial femorotibial compartment cartilage thickness at 6 months and 12 months as determined using quantitative magnetic resonance imaging (qMRI). The primary safety end points were nature, incidence, and severity of local and systemic treatment-emergent adverse events (AEs) and acute inflammatory reactions, as well as results of laboratory assessments. Secondary end points included changes in total and compartment femorotibial cartilage thickness and volume as assessed by qMRI, changes in joint space width (JSW) seen on radiographs, and pain scores on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).

RESULTS

One hundred ninety-two patients were randomized and evaluated for safety, 180 completed the trial, and 168 were evaluated for the primary efficacy end point. We found no statistically significant dose response in change in central medial femorotibial compartment cartilage thickness. Sprifermin was associated with statistically significant, dose-dependent reductions in loss of total and lateral femorotibial cartilage thickness and volume and in JSW narrowing in the lateral femorotibial compartment. All groups had improved WOMAC pain scores, with statistically significantly less improvement at 12 months in patients receiving the 100-μg dose of sprifermin as compared with those receiving placebo. There was no significant difference in serious AEs, treatment-emergent AEs, or acute inflammatory reactions between sprifermin and placebo groups.

CONCLUSION

No statistically significant relationship between treatment group and reduction in central medial femorotibial compartment cartilage thickness was observed; however, prespecified structural secondary end points showed statistically significant dose-dependent reductions after sprifermin treatment. Sprifermin was not associated with any local or systemic safety concerns.

Development of a rapid knee cartilage damage quantification method using magnetic resonance images

BACKGROUND

Cartilage morphometry based on magnetic resonance images (MRIs) is an emerging outcome measure for clinical trials among patients with knee osteoarthritis (KOA). However, current methods for cartilage morphometry take many hours per knee and require extensive training on the use of the associated software. In this study we tested the feasibility, reliability, and construct validity of a novel osteoarthritis cartilage damage quantification method (Cartilage Damage Index [CDI]) that utilizes informative locations on knee MRIs.

METHODS

We selected 102 knee MRIs from the Osteoarthritis Initiative that represented a range of KOA structural severity (Kellgren Lawrence [KL] Grade 0 - 4). We tested the intra- and inter-tester reliability of the CDI and compared the CDI scores against different measures of severity (radiographic joint space narrowing [JSN] grade, KL score, joint space width [JSW]) and static knee alignment, both cross-sectionally and longitudinally.

RESULTS

Determination of the CDI took on average14.4 minutes (s.d. 2.1) per knee pair (baseline and follow-up of one knee). Repeatability was good (intra- and inter-tester reliability: intraclass correlation coefficient >0.86). The mean CDI scores related to all four measures of osteoarthritis severity (JSN grade, KL score, JSW, and knee alignment; all p values < 0.05). Baseline JSN grade and knee alignment also predicted subsequent 24-month longitudinal change in the CDI (p trends <0.05). During 24 months, knees with worsening in JSN or KL grade (i.e. progressors) had greater change in CDI score.

CONCLUSIONS

The CDI is a novel knee cartilage quantification method that is rapid, reliable, and has construct validity for assessment of medial tibiofemoral osteoarthritis structural severity and its progression. It has the potential to addresses the barriers inherent to studies requiring assessment of cartilage damage on large numbers of knees, and as a biomarker for knee osteoarthritis progression.

The role of imaging in osteoarthritis

Osteoarthritis (OA) is the most prevalent joint disorder with no approved disease-modifying treatment available. The importance of imaging in assessing all joint structures involved in the disease process, including articular cartilage, meniscus, subarticular bone marrow, and synovium for diagnosis, prognostication, and follow-up, has been well recognized. In daily clinical practice, conventional radiography is still the most commonly used imaging technique for the evaluation of a patient with known or suspected OA and radiographic outcome measures are still the only approved end point by regulatory authorities in clinical trials. The ability of magnetic resonance imaging (MRI) to visualize all joint structures in three-dimensional fashion including tissue ultrastructure has markedly deepened our understanding of the natural history of the disease. This article describes the roles and limitations of different imaging modalities for clinical practice and research in OA, with a focus on radiography and MRI and an emphasis on the knee joint.

A preference-based single-item measure of quality of life following medial opening wedge high tibial osteotomy: large improvements similar to arthroplasty

BACKGROUND

Improvements in generic and disease specific scores have been reported with medial opening wedge high tibial osteotomy (MOW HTO). However, meaningful comparisons between competing surgical interventions have been hampered by the lack of a preference based single index of health related quality of life (HRQoL). The primary aim of this study was to derive and report a single index measure of HRQoL for patients undergoing MOW HTO, preoperatively and at 12 and 24 postoperatively. Secondary aims were to evaluate changes in various additional measures of quality of life at these time points.

METHODS

The impact of MOW HTO was evaluated using generic and disease specific instruments. One hundred thirty eight patients completed the Medical Outcomes Study short form health survey (SF-12) and Knee Osteoarthritis Outcomes Score (KOOS) before, 12 and 24 months after surgery. A preference-based single index measure of HRQoL was calculated and changes were evaluated.

RESULTS

The mean change in the HRQoL suggested large, clinically significant improvements from 0.69 preoperatively to 0.82 (p<0.001) and 0.8 at 12 and 24 months postoperatively respectively. All dimensions of the SF-12, except role mental health, and all dimensions of the KOOS also demonstrated statistically significant improvements between pre and postoperative measurements.

CONCLUSIONS

The preoperative HRQoL of young patients with mechanical varus alignment and medial compartment knee osteoarthritis is similar to older patients with knee osteoarthritis. Medial opening wedge high tibial osteomoty results in significant improvements in HRQoL, the magnitude of which is comparable to other surgical interventions for knee osteoarthristis.

Lateral and medial joint space narrowing predict subsequent cartilage loss in the narrowed, but not in the non-narrowed femorotibial compartment--data from the Osteoarthritis Initiative

OBJECTIVE

To determine the predictive value of unicompartimental joint space narrowing (JSN) for MRI-based cartilage thickness loss in the narrowed and the non-narrowed femorotibial compartment.

METHODS

922 knees from 922 Osteoarthritis Initiative (OAI) participants (62.2 ± 9.0 years, 61% females) with radiographic OA (158 without JSN [noJSN], 175 with lateral JSN [latJSN], 589 with medial JSN [medJSN]) were analyzed using 3 T MRI. One-year cartilage thickness change was determined in the lateral (LFTC) and medial femorotibial compartment (MFTC), and in femorotibial subregions. The probability of subsequent cartilage loss was calculated using predefined thresholds. The predictive value of JSN for the probability and magnitude of cartilage loss was compared between latJSN, medJSN and noJSN knees using Fisher's exact and Mann-Whitney-U tests.

RESULTS

The probability of cartilage loss was greater in the narrowed compartment of latJSN/medJSN knees (34.9%/32.4%) than in noJSN knees (13.3%/12.7%, P ≤ 6.4 × 10(-6)) and so was the magnitude of cartilage thickness change (P ≤ 8.2 × 10(-6)). No significant differences were observed between the narrowed compartments of latJSN vs. medJSN knees (probability: P = 0.58, magnitude: P = 0.19) or between the non-narrowed compartment of latJSN/medJSN vs. noJSN knees (probability: P ≥ 0.35, magnitude: P = ≥0.23). These results were confirmed by the location-independent ordered value (OV) analyses of femorotibial subregions.

CONCLUSION

The predictive value of latJSN for lateral compartment cartilage loss was comparable to that of medJSN for medial compartment cartilage loss, whereas cartilage loss in the non-narrowed compartment was similar to that in noJSN knees. These findings provide important clues to predicting progression of knee OA, and in tailoring inclusion criteria for clinical trials.

Relationship between knee pain and the presence, location, size and phenotype of femorotibial denuded areas of subchondral bone as visualized by MRI

OBJECTIVE

Conflicting associations between imaging biomarkers and pain in knee osteoarthritis (OA) have been reported. A relation between pain and denuded areas of subchondral bone (dABs) has been suggested and this study explores this relationship further by relating the presence, phenotype, location and size of dABs to different measures of knee pain.

METHODS

633 right knees from the Osteoarthritis Initiative (OAI) (250 men, age 61.7 ± 9.6 yrs, BMI 29.4 ± 4.7 kg/m(2)) were included. Manual segmentation of the femorotibial cartilage plates was performed on 3 T coronal fast low angle shot with water excitation (FLASHwe) images. dABs were defined as areas where the subchondral bone was uncovered by cartilage. The following measures of pain were used: weightbearing-, non-weightbearing-, moderate-to-severe-, infrequent- and frequent knee pain.

RESULTS

Using pain measures from subjects without dABs as a reference, those with at least one dAB had a 1.64-fold higher prevalence ratio [PR, 95% confidence interval (CI) 1.24-2.18] to have frequent and 1.45-fold higher for moderate-to-severe knee pain (95% CI 1.13-1.85). Subjects with dABs in central subregions had a 1.53-fold increased prevalence of having weightbearing pain (95% CI 1.20-1.97), especially when the central subregion was moderately (>10%) denuded (PR 1.81, 95% CI 1.35-2.42). Individuals with cartilage-loss-type dABs had a slightly higher prevalence (PR 1.13, 95% CI 1.00-1.27) of having frequent knee pain compared to individuals with intra-chondral-osteophyte-type dABs.

CONCLUSION

This study supports a positive relation between femorotibial dABs and knee pain, especially when the dABs are located centrally (i.e., in weightbearing regions) or when the respective central subregion is moderately denuded.