Aims. As has been shown in larger animal models, knee immobilization can lead to arthrofibrotic phenotypes. Our study included 168 C57BL/6J female mice, with 24 serving as controls, and 144 undergoing a knee procedure to induce a contracture without osteoarthritis (OA). Methods. Experimental knees were immobilized for either four weeks (72 mice) or eight weeks (72 mice), followed by a remobilization period of zero weeks (24 mice), two weeks (24 mice), or four weeks (24 mice) after suture removal. Half of the experimental knees also received an intra-articular injury. Biomechanical data were collected to measure passive extension angle (PEA). Histological data measuring area and thickness of posterior and anterior knee capsules were collected from knee sections. Results. Experimental knees immobilized for four weeks demonstrated mean PEAs of 141°, 72°, and 79° after zero, two, and four weeks of remobilization (n = 6 per group), respectively. Experimental knees demonstrated reduced PEAs after two weeks (p < 0.001) and four weeks (p < 0.0001) of remobilization compared to controls. Following eight weeks of immobilization, experimental knees exhibited mean PEAs of 82°, 73°, and 72° after zero, two, and four weeks of remobilization, respectively. Histological analysis demonstrated no cartilage degeneration. Similar trends in biomechanical and histological properties were observed when intra-articular violation was introduced. Conclusion. This study established a novel mouse model of robust knee contracture without evidence of OA. This was appreciated consistently after eight weeks of immobilization and was irrespective of length of remobilization. As such, this arthrofibrotic model provides opportunities to investigate molecular pathways and therapeutic strategies. Cite this article: Bone Joint Res 2023;12(1):58–71

Aims. While mechanical alignment (MA) is the traditional technique in total knee arthroplasty (TKA), its potential for altering constitutional alignment remains poorly understood. This study aimed to quantify unintentional changes to constitutional coronal alignment and joint line obliquity (JLO) resulting from MA. Methods. A retrospective cohort study was undertaken of 700 primary MA TKAs (643 patients) performed between 2014 and 2017. Lateral distal femoral and medial proximal tibial angles were measured pre- and postoperatively to calculate the arithmetic hip-knee-ankle angle (aHKA), JLO, and Coronal Plane Alignment of the Knee (CPAK) phenotypes. The primary outcome was the magnitude and direction of aHKA, JLO, and CPAK alterations. Results. The mean aHKA and JLO increased by 0.1° (SD 3.4°) and 5.8° (SD 3.5°), respectively, from pre- to postoperatively. The most common phenotypes shifted from 76.3% CPAK Types I, II, or III (apex distal JLO) preoperatively to 85.0% IV, V, or VI (apex horizontal JLO) postoperatively. The proportion of knees with apex proximal JLO increased from 0.7% preoperatively to 11.1% postoperatively. Among all MA TKAs, 60.0% (420 knees) were changed from their constitutional alignments into CPAK Type V, while 40.0% (280 knees) either remained in constitutional Type V (5.0%, 35 knees) or were unintentionally aligned into other CPAK types (35.0%; 245 knees). Conclusion. Fixed MA targets in TKA lead to substantial changes from constitutional alignment, primarily a significant increase in JLO. These findings enhance our understanding of alignment alterations resulting from both unintended changes to knee phenotypes and surgical resection imprecision. Cite this article: Bone Jt Open 2024;5(2):109–116

Aims. The Coronal Plane Alignment of the Knee (CPAK) classification has been developed to predict individual variations in inherent knee alignment. The impact of preoperative and postoperative CPAK classification phenotype on the postoperative clinical outcomes of total knee arthroplasty (TKA) remains elusive. This study aimed to examine the effect of postoperative CPAK classification phenotypes (I to IX), and their pre- to postoperative changes on patient-reported outcome measures (PROMs). Methods. A questionnaire was administered to 340 patients (422 knees) who underwent primary TKA for osteoarthritis (OA) between September 2013 and June 2019. A total of 231 patients (284 knees) responded. The ­Knee Society Score 2011 (KSS 2011), Knee injury and Osteoarthritis Outcome Score-12 (KOOS-12), and Forgotten Joint Score-12 (FJS-12) were used to assess clinical outcomes. Using preoperative and postoperative anteroposterior full-leg radiographs, the arithmetic hip-knee-ankle angle (aHKA) and joint line obliquity (JLO) were calculated and classified based on the CPAK classification. To investigate the impact on PROMs, multivariable regression analyses using stepwise selection were conducted, considering factors such as age at surgery, time since surgery, BMI, sex, implant use, postoperative aHKA classification, JLO classification, and changes in aHKA and JLO classifications from preoperative to postoperative. Results. The preoperative and postoperative CPAK classifications were predominantly phenotype I (155 knees; 55%) and phenotype V (73 knees; 26%), respectively. The change in the preoperative to postoperative aHKA classification was a significant negative predictive factor for KOOS-12 and FJS-12, while postoperative apex proximal JLO was a significant negative predictive factor for KSS 2011 and KOOS-12. Conclusion. In primary TKA for OA, preoperative and postoperative CPAK phenotypes were associated with PROMs. Alteration in varus/valgus alignment from preoperative to postoperative was recognized as a negative predictive factor for both KOOS-12 and FJS-12. Moreover, the postoperative apex proximal JLO was identified as a negative factor for KSS 2011 and KOOS-12. Determining the target alignment for each preoperative phenotype with reproducibility could improve PROMs. Cite this article: Bone Joint J 2024;106-B(10):1059–1066

Aims. Functional alignment (FA) in total knee arthroplasty (TKA) aims to achieve balanced gaps by adjusting implant positioning while minimizing changes to constitutional joint line obliquity (JLO). Although FA uses kinematic alignment (KA) as a starting point, the final implant positions can vary significantly between these two approaches. This study used the Coronal Plane Alignment of the Knee (CPAK) classification to compare differences between KA and final FA positions. Methods. A retrospective analysis compared pre-resection and post-implantation alignments in 2,116 robotic-assisted FA TKAs. The lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) were measured to determine the arithmetic hip-knee-ankle angle (aHKA = MPTA – LDFA), JLO (JLO = MPTA + LDFA), and CPAK type. The primary outcome was the proportion of knees that varied ≤ 2° for aHKA and ≤ 3° for JLO from their KA to FA positions, and direction and magnitude of those changes per CPAK phenotype. Secondary outcomes included proportion of knees that maintained their CPAK phenotype, and differences between sexes. Results. Overall, 71.6% had an aHKA change ≤ 2°, and 87.0% a JLO change ≤ 3°. Mean aHKA changed from -1.1° (SD 2.8°) in KA to -1.9° (SD 2.3°) in FA (mean difference (MD) -0.83 (SD 2.0); p < 0.001). Mean JLO changed from 173.9° (SD 3.0°) in KA to 174.2° (SD 2.6°) in FA (MD 0.38 (SD 2.3); p < 0.001). CPAK type was maintained in 58.1% of knees, with the proportion highest for Types I (73.9%), II (61.1%), and IV (51.2%). In valgus knees, 67.5% of Type III and 71.7% of Type VI were shifted to neutral phenotypes. There was minimal change to constitutional JLO across all CPAK types (MDs -2.0° to 1.2°). Conclusion. Functional alignment may alter CPAK type, but does not significantly change JLO. A kinematic starting point minimizes changes to native anatomy, while final position with FA provides an optimally balanced TKA. Cite this article: Bone Jt Open 2024;5(12):1081–1091

Aims. A comprehensive classification for coronal lower limb alignment with predictive capabilities for knee balance would be beneficial in total knee arthroplasty (TKA). This paper describes the Coronal Plane Alignment of the Knee (CPAK) classification and examines its utility in preoperative soft tissue balance prediction, comparing kinematic alignment (KA) to mechanical alignment (MA). Methods. A radiological analysis of 500 healthy and 500 osteoarthritic (OA) knees was used to assess the applicability of the CPAK classification. CPAK comprises nine phenotypes based on the arithmetic HKA (aHKA) that estimates constitutional limb alignment and joint line obliquity (JLO). Intraoperative balance was compared within each phenotype in a cohort of 138 computer-assisted TKAs randomized to KA or MA. Primary outcomes included descriptive analyses of healthy and OA groups per CPAK type, and comparison of balance at 10° of flexion within each type. Secondary outcomes assessed balance at 45° and 90° and bone recuts required to achieve final knee balance within each CPAK type. Results. There was similar frequency distribution between healthy and arthritic groups across all CPAK types. The most common categories were Type II (39.2% healthy vs 32.2% OA), Type I (26.4% healthy vs 19.4% OA) and Type V (15.4% healthy vs 14.6% OA). CPAK Types VII, VIII, and IX were rare in both populations. Across all CPAK types, a greater proportion of KA TKAs achieved optimal balance compared to MA. This effect was largest, and statistically significant, in CPAK Types I (100% KA vs 15% MA; p < 0.001), Type II (78% KA vs 46% MA; p = 0.018). and Type IV (89% KA vs 0% MA; p < 0.001). Conclusion. CPAK is a pragmatic, comprehensive classification for coronal knee alignment, based on constitutional alignment and JLO, that can be used in healthy and arthritic knees. CPAK identifies which knee phenotypes may benefit most from KA when optimization of soft tissue balance is prioritized. Further, it will allow for consistency of reporting in future studies. Cite this article: Bone Joint J 2021;103-B(2):329–337

Aims. The Coronal Plane Alignment of the Knee (CPAK) classification is a simple and comprehensive system for predicting pre-arthritic knee alignment. However, when the CPAK classification is applied in the Asian population, which is characterized by more varus and wider distribution in lower limb alignment, modifications in the boundaries of arithmetic hip-knee-ankle angle (aHKA) and joint line obliquity (JLO) should be considered. The purposes of this study were as follows: first, to propose a modified CPAK classification based on the actual joint line obliquity (aJLO) and wider range of aHKA in the Asian population; second, to test this classification in a cohort of Asians with healthy knees; third, to propose individualized alignment targets for different CPAK types in kinematically aligned (KA) total knee arthroplasty (TKA). Methods. The CPAK classification was modified by changing the neutral boundaries of aHKA to 0° ± 3° and using aJLO as a new variable. Radiological analysis of 214 healthy knees in 214 Asian individuals was used to assess the distribution and mean value of alignment angles of each phenotype among different classifications based on the coronal plane. Individualized alignment targets were set according to the mean lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) of different knee types. Results. A very high concentration, 191 from 214 individuals (89.3%), were found in knee types with apex distal JLO when the CPAK classification was applied in the Asian population. By using aJLO as a new variable, the high distribution percentage in knee types with apex distal JLO decreased to 125 from 214 individuals (58.4%). The most common types in order were Type II (n = 70; 32.7%), Type V (n = 55; 25.7%), and Type I (n = 46; 21.5%) in the modified CPAK classification. Conclusion. The modified CPAK classification corrected the uneven distribution when applying the CPAK classification in the Asian population. Setting individualized TKA alignment targets according to CPAK type may be a practical method to recreate optimal LDFA and MPTA in KA-TKA. Cite this article: Bone Jt Open 2022;3(3):211–217

Aims

Adenosine, lidocaine, and Mg²⁺ (ALM) therapy exerts differential immuno-inflammatory responses in males and females early after anterior cruciate ligament (ACL) reconstruction (ACLR). Our aim was to investigate sex-specific effects of ALM therapy on joint tissue repair and recovery 28 days after surgery.

Aims

The aims of this study were: 1) to describe extended restricted kinematic alignment (E-rKA), a novel alignment strategy during robotic-assisted total knee arthroplasty (RA-TKA); 2) to compare residual medial compartment tightness following virtual surgical planning during RA-TKA using mechanical alignment (MA) and E-rKA, in the same set of osteoarthritic varus knees; 3) to assess the requirement of soft-tissue releases during RA-TKA using E-rKA; and 4) to compare the accuracy of surgical plan execution between knees managed with adjustments in component positioning alone, and those which require additional soft-tissue releases.

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This study examined windswept deformity (WSD) of the knee, comparing prevalence and contributing factors in healthy and osteoarthritic (OA) cohorts.

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The surgical target for optimal implant positioning in robotic-assisted total knee arthroplasty remains the subject of ongoing discussion. One of the proposed targets is to recreate the knee’s functional behaviour as per its pre-diseased state. The aim of this study was to optimize implant positioning, starting from mechanical alignment (MA), toward restoring the pre-diseased status, including ligament strain and kinematic patterns, in a patient population.

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This study aimed to explore the biological and clinical importance of dysregulated key genes in osteoarthritis (OA) patients at the cartilage level to find potential biomarkers and targets for diagnosing and treating OA.

Aims

The impact of a diaphyseal femoral deformity on knee alignment varies according to its severity and localization. The aims of this study were to determine a method of assessing the impact of diaphyseal femoral deformities on knee alignment for the varus knee, and to evaluate the reliability and the reproducibility of this method in a large cohort of osteoarthritic patients.

Aims

Accurate identification of the ankle joint centre is critical for estimating tibial coronal alignment in total knee arthroplasty (TKA). The purpose of the current study was to leverage artificial intelligence (AI) to determine the accuracy and effect of using different radiological anatomical landmarks to quantify mechanical alignment in relation to a traditionally defined radiological ankle centre.

Aims

Outcomes of current operative treatments for arthrofibrosis after total knee arthroplasty (TKA) are not consistently positive or predictable. Pharmacological in vivo studies have focused mostly on prevention of arthrofibrosis. This study used a rabbit model to evaluate intra-articular (IA) effects of celecoxib in treating contracted knees alone, or in combination with capsular release.

Aims

The aim of this study was to screen the entire genome for genetic markers associated with risk for anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) injury.

Objectives

Our objective in this article is to test the hypothesis that type 2 diabetes mellitus (T2DM) is a factor in the onset and progression of osteoarthritis, and to characterise the quality of the articular cartilage in an appropriate rat model.

Objectives

The lack of effective treatment for cartilage defects has prompted investigations using tissue engineering techniques for their regeneration and repair. The success of tissue-engineered repair of cartilage may depend on the rapid and efficient adhesion of transplanted cells to a scaffold. Our aim in this study was to repair full-thickness defects in articular cartilage in the weight-bearing area of a porcine model, and to investigate whether the CD44 monoclonal antibody biotin-avidin (CBA) binding technique could provide satisfactory tissue-engineered cartilage.

Objectives

Matrix-assisted autologous chondrocyte transplantation (MACT) has been developed and applied in the clinical practice in the last decade to overcome most of the disadvantages of the first generation procedures. The purpose of this systematic review is to document and analyse the available literature on the results of MACT in the treatment of chondral and osteochondral lesions of the knee.