Midterm Outcomes After Total Knee Arthroplasty With Lateral Approach for Valgus Knee Deformity in Patients With Rheumatoid Arthritis.

Background Valgus knee deformity is often seen in rheumatoid arthritis (RA) cases. Usually, the medial approach has been often utilized for total knee arthroplasty (TKA), even in valgus deformity cases; however, the medial approach is feared to induce further instability in the medial side because it could further break the soft tissue structure, including medial collateral ligament (MCL) and medial patellofemoral ligament (MPFL). Consequently, loosening of the implant, recurrence of valgus knee deformity, and pain due to instability might be induced in the early period after surgery. In this study, a lateral approach for TKA against valgus deformity in RA cases was utilized to avoid further damage on the medial side. Methods Eleven valgus knees in 10 patients with RA (mean age, 61.1 years; mean follow-up, 33.1 months) underwent primary TKA with the lateral approach. Iliotibial band (ITB) dissection and/or peroneal nerve release were performed if necessary. Radiological and clinical investigations were evaluated pre- and postoperatively. Results The average operating time was 106 minutes, which was no longer compared with the time after the medial approach described previously. The extension angle was significantly improved from -15.0 ± 10.2 to -5.5 ± 4.2 degrees (P = 0.03), while the flexion angle showed no significant change (from 111.8 ± 15.9 to 115.0 ± 13.2 degrees). The hip-knee-ankle angle (HKA) was also significantly corrected from -9 ± 4.9 to 0.4 ± 1.7 degrees (P < 0.001). The 2011 Knee Score System (KSS) scores were significantly improved from 6.9 ± 3.4 to 21.5 ± 2.9 (P < 0.001) in symptoms, from 15.6 ± 2.7 to 31.1 ± 4.1 (P < 0.001) in satisfaction, and from 31.5 to 59.5 (P < 0.01) in activity. Conclusion Midterm outcomes after lateral approach TKA were good, and knee alignment was significantly improved. The lateral approach TKA for valgus deformity in patients with RA was not complicated and difficult because it required no additional operating time compared with the medial approach. From the perspective of preventing further damage to the soft tissue structure on the medial side, the lateral approach was meaningful for valgus deformity in patients with RA.

Comparison of effectiveness of methotrexate in patients with late-onset versus younger-onset rheumatoid arthritis: Real-world data from an inception cohort in Japan (NICER-J).

OBJECTIVE: To compare the effectiveness of methotrexate (MTX) as initial therapy in patients with late-onset and younger-onset rheumatoid arthritis (LORA and YORA). METHODS: Of 114 patients with YORA and 96 patients with LORA, defined as RA occurring at ≥65 years of age, enrolled in a multicentre RA inception cohort study, 71 and 66 patients who had been followed up to 6 months after starting MTX treatment were included in this study. RESULTS: Proportions of patients on MTX treatment at 6 months were 96% and 92% in the YORA and LORA groups, respectively. Despite lower doses of MTX in the LORA group compared with the YORA group, no significant difference was observed in clinical disease activity index scores between the two groups throughout the follow-up period. The proportion of patients in clinical disease activity index remission at 6 months was 35% in both groups. Logistic regression analysis revealed that knee joint involvement and high Health Assessment Questionnaire-Disability Index were significant negative predictors of achieving clinical disease activity index remission at 6 months in the LORA group. CONCLUSION: Observations up to 6 months revealed that the effectiveness of MTX administered based on rheumatologist discretion in patients with LORA is comparable to that in patients with YORA in clinical settings.

Iguratimod suppresses sclerostin and receptor activator of NF-κB ligand production via the extracellular signal-regulated kinase/early growth response protein 1/tumor necrosis factor alpha pathway in osteocytes and ameliorates disuse osteoporosis in mice.

Disuse osteoporosis is a prevalent complication among patients afflicted with rheumatoid arthritis (RA). Although reports have shown that the antirheumatic drug iguratimod (IGU) ameliorates osteoporosis in RA patients, details regarding its effects on osteocytes remain unclear. The current study examined the effects of IGU on osteocytes using a mouse model of disuse-induced osteoporosis, the pathology of which crucially involves osteocytes. A reduction in distal femur bone mass was achieved after 3 weeks of hindlimb unloading in mice, which was subsequently reversed by intraperitoneal IGU treatment (30 mg/kg; five times per week). Histology revealed that hindlimb-unloaded (HLU) mice had significantly increased osteoclast number and sclerostin-positive osteocyte rates, which were suppressed by IGU treatment. Moreover, HLU mice exhibited a significant decrease in osteocalcin-positive cells, which was attenuated by IGU treatment. In vitro, IGU suppressed the gene expression of receptor activator of NF-κB ligand (RANKL) and sclerostin in MLO-Y4 and Saos-2 cells, which inhibited osteoclast differentiation of mouse bone marrow cells in cocultures. Although IGU did not affect the nuclear translocation or transcriptional activity of NF-κB, RNA sequencing revealed that IGU downregulated the expression of early growth response protein 1 (EGR1) in osteocytes. HLU mice showed significantly increased EGR1- and tumor necrosis factor alpha (TNFα)-positive osteocyte rates, which were decreased by IGU treatment. EGR1 overexpression enhanced the gene expression of TNFα, RANKL, and sclerostin in osteocytes, which was suppressed by IGU. Contrarily, small interfering RNA-mediated suppression of EGR1 downregulated RANKL and sclerostin gene expression. These findings indicate that IGU inhibits the expression of EGR1, which may downregulate TNFα and consequently RANKL and sclerostin in osteocytes. These mechanisms suggest that IGU could potentially be used as a treatment option for disuse osteoporosis by targeting osteocytes.

An investigation of the differential therapeutic effects of romosozumab on postmenopausal osteoporosis patients with or without rheumatoid arthritis complications: a case-control study.

The impact of ROMO on the width of anabolic windows and the increase in BMD was reduced in the RA group compared to the non-RA group, and this reduction was associated with correlations to RA-related factors. PURPOSE: To investigate the effects of romosozumab (ROMO) in postmenopausal osteoporosis, with and without comorbid rheumatoid arthritis (RA). METHODS: In this retrospective, case-controlled, multicenter study, 171 postmenopausal patients who did not receive oral glucocorticoid, comprising 59 in the RA group and 121 in the non-RA group, received uninterrupted ROMO treatment for 12 months. Propensity score matching was employed to ensure comparability in clinical backgrounds, resulting in 41 patients in each group. Baseline characteristics were as follows: overall (mean age, 76.3 years; T-score of lumbar spine (LS), - 3.0; 45.1% were treatment-naive for osteoporosis); RA group (anti-cyclic citrullinated peptide antibody (ACPA) positivity, 80.5%; titer, 206.2 U/ml; clinical disease activity index (CDAI), 13.6; health assessment questionnaire disability index (HAQ-DI), 0.9). Bone mineral density (BMD) and serum bone turnover markers were monitored over a 12-month period. RESULTS: The rate of increase in the bone formation marker, PINP, and the rates of decrease in the bone resorption marker, TRACP-5b, exhibited a trend toward smaller changes in the RA group compared to the non-RA group, implying a smaller anabolic window. After 12 months, the RA group displayed lower BMD increases in the LS (9.1% vs. 12.6%; P = 0.013) and total hip (2.4% vs. 4.8%; P = 0.025) compared to the non-RA group. Multiple regression analysis in the all RA group (n = 59) for the association between RA-specific factors and 12-month BMD changes revealed negative correlations between ACPA titer and LS BMD and between HAQ-DI and femoral neck BMD. CONCLUSIONS: The efficacy of ROMO may be attenuated by RA-related factors.

Reverse V-shaped osteotomy for ankylosing rocker-bottom foot deformity in patients with rheumatoid arthritis. A report of 3 cases.

This study evaluated reverse V-shaped osteotomy for ankylosing rocker-bottom foot deformity in patients with rheumatoid arthritis. We experienced 3 feet: rheumatoid rocker-bottom deformities with painful and/or infectious bony prominence towards the bottom of the foot, treated with a reverse V-shaped osteotomy in the mid-hindfoot. In all three cases, significant correction was achieved with restoration of the medial longitudinal arch, and improvement in clinical scores was confirmed. Reverse V-shaped osteotomy has the potential to be a useful and definitive procedure for ankylosing rocker-bottom deformity in patients with rheumatoid arthritis.

Early full weight-bearing and gait exercise after cemented total ankle arthroplasty with modified antero-lateral approach.

BACKGROUND: According to the conventional postoperative procedure after total ankle arthroplasty (TAA) against end-stage osteoarthritis (OA) and rheumatoid arthritis (RA), mobilization and weight-bearing is currently started after completion of wound healing. Recently, early mobilization for dorsiflexion after TAA with modified antero-lateral approach was reported to be feasible and safe. To investigate the further possibility of expediting rehabilitation, this study evaluated the feasibility and safety of early full weight-bearing and gait exercise after cemented TAA utilizing a modified antero-lateral approach. MATERIALS AND METHODS: This retrospective, observational study investigated 23 consecutive ankles (OA: 14 ankles, RA: 9 ankles) that had received cemented TAA with a modified antero-lateral approach. These ankles were divided into three groups [1. conventional postoperative protocol: 8 ankles, 2. early dorsiflexion protocol: 7 ankles, 3. early dorsiflexion+full weight-bearing protocol: 8 ankles]. In group 3, after early dorsiflexion mobilization (day 3), full weight-bearing/gait exercise was started from 7 days after surgery (10 days after if malleolar osteotomy was added). Postoperative wound complications were observed and recorded. Number of days for hospitalization was also evaluated. Range of motion (ROM) of dorsiflexion/plantar flexion was measured. Patients also completed a self-administered foot evaluation questionnaire (SAFE-Q) and the scale of Japanese Society for Surgery of the Foot (JSSF) ankle/hindfoot score preoperatively and at final follow-up. RESULTS: No postoperative complications related to wound healing were observed even after early full weight-bearing and gait exercise. Days for hospitalization was significantly shortened in early full weight-bearing and gait exercise group (group 3) from 35-38 days to 24 days. ROM for both dorsiflexion and plantar flexion significantly increased in group 3, furthermore all indices of SAFE-Q score also showed stronger significant improvement in group 3. JSSF score improved significantly after TAA in all groups. CONCLUSION: Within this small number of cases, early full weight-bearing and gait exercise from 7 days after cemented TAA was feasible and safe with the modified antero-lateral approach. Combination of early dorsiflexion mobilization and weight-bearing/gait exercise contributed to shortening the hospitalization day, and improving ROM for both dorsiflexion and plantar flexion after surgery. Innovations in postoperative procedures for rehabilitation after TAA can be expected.

Associations of disease duration and anti-citrullinated peptide antibody status with the effectiveness of abatacept in biologic-naïve patients with rheumatoid arthritis: Post hoc analysis of a multicentre, real-world observational study in Japan (ORIGAMI).

OBJECTIVES: The aim of the article is to investigate the associations of disease duration and anti-cyclic citrullinated peptide antibody (ACPA) status with the effectiveness of abatacept in biologic-naïve patients with rheumatoid arthritis (RA). METHODS: We performed post hoc analyses of the Orencia® Registry in Geographically Assembled Multicenter Investigation (ORIGAMI) study of biologic-naïve RA patients aged ≥20 years with moderate disease activity who were prescribed abatacept. Changes in the Simplified Disease Activity Index (SDAI) and Japanese Health Assessment Questionnaire (J-HAQ) at 4, 24, and 52 weeks of treatment were analysed in patients divided according to ACPA serostatus (positive/negative), disease duration (<1/≥1 year), or both. RESULTS: SDAI scores decreased from baseline in all groups. SDAI scores tended to decrease more in the ACPA-positive group and disease duration <1-year group than in the ACPA-negative group and disease duration ≥1-year group, respectively. In the disease duration <1-year group, SDAI tended to decrease more in the ACPA-positive group than in the ACPA-negative group. Disease duration was independently associated with the change in SDAI and SDAI remission at Week 52 in multivariable regression models. CONCLUSIONS: These results suggest that starting abatacept within 1 year of diagnosis was associated with greater effectiveness of abatacept in biologic-naïve patients with RA and moderate disease activity.

Anti-NF-κB peptide derived from nuclear acidic protein attenuates ovariectomy-induced osteoporosis in mice.

NF-κB is a transcription factor that is activated with aging. It plays a key role in the development of osteoporosis by promoting osteoclast differentiation and inhibiting osteoblast differentiation. In this study, we developed a small anti-NF-κB peptide called 6A-8R from a nuclear acidic protein (also known as macromolecular translocation inhibitor II, Zn2+-binding protein, or parathymosin) that inhibits transcriptional activity of NF-κB without altering its nuclear translocation and binding to DNA. Intraperitoneal injection of 6A-8R attenuated ovariectomy-induced osteoporosis in mice by inhibiting osteoclast differentiation, promoting osteoblast differentiation, and inhibiting sclerostin production by osteocytes in vivo with no apparent side effects. Conversely, in vitro, 6A-8R inhibited osteoclast differentiation by inhibiting NF-κB transcriptional activity, promoted osteoblast differentiation by promoting Smad1 phosphorylation, and inhibited sclerostin expression in osteocytes by inhibiting myocyte enhancer factors 2C and 2D. These findings suggest that 6A-8R has the potential to be an antiosteoporotic therapeutic agent with uncoupling properties.

Quick Transposition of ReBOSSIS-J® to the Host Bone Trabeculae Within One Month After Supplementing to the Harvest Site on the Calcaneus for Autologous Bone Grafting in a Rheumatoid Arthritis Case.

We present the case of a patient with rheumatoid arthritis who underwent talonavicular joint fusion using an autologous calcaneal bone graft. At the same time, the bony defect at the harvest site was supplemented with ReBOSSIS-J® [70% ß-TCP and 30% poly(L-lactide-co-glycolide)](ORTHOREBIRTH Co. Ltd., Kanagawa, Japan), a synthetic bioresorbable bone void filler for the repair of bony defects with handling characteristics similar to a cotton ball. Material resorption and new bone formation had already started one week postoperatively. Transposition to host bone trabeculae was almost completed by 26 days postoperatively. Very rapid reactive graft resorption, repair with new bone formation, and subsequently, most of the transformation to host bone trabeculae were confirmed. ReBOSSIS-J® appears feasible to contribute to early heel weight-bearing exercise after foot or ankle surgery. In addition, preventing the fracture at the harvesting site of the calcaneal bone graft can also be expected.

Angioleiomyoma mimicking a swollen bursa on first metatarsophalangeal joint accompanying with hallux valgus deformity.

We present a case of a patient who underwent a modified scarf osteotomy and tumour excision based on a preoperative diagnosis of hallux valgus deformity and accompanying bursitis. Subsequent histopathological examination revealed that the tumour was an angioleiomyoma. While tumours around the first metatarsophalangeal (MTP) joint are typically associated with gouty nodules, infections, or swollen bursa (bursitis) in patients with hallux valgus deformity, the occurrence of soft tissue tumours in this area is rare. Moreover, angioleiomyoma is an even rarer form of soft tissue tumour and is seldom suspected prior to resection. To our knowledge, there have been no reports of angioleiomyoma arising in the first MTP joint. However, it is important to consider the possibility of an atypical tumour in cases where soft tissue masses are present, even in patients with hallux valgus deformity, and to perform at least imaging tests such as ultrasound and magnetic resonance imaging before surgery. This prospect should always be kept in mind.

Drug retention of biologics and Janus kinase inhibitors in patients with rheumatoid arthritis: the ANSWER cohort study.

OBJECTIVES: This multicentre retrospective study in Japan aimed to assess the retention of biological disease-modifying antirheumatic drugs and Janus kinase inhibitors (JAKi), and to clarify the factors affecting their retention in a real-world cohort of patients with rheumatoid arthritis. METHODS: The study included 6666 treatment courses (bDMARD-naïve or JAKi-naïve cases, 55.4%; tumour necrosis factor inhibitors (TNFi) = 3577; anti-interleukin-6 receptor antibodies (aIL-6R) = 1497; cytotoxic T lymphocyte-associated antigen-4-Ig (CTLA4-Ig) = 1139; JAKi=453 cases). The reasons for discontinuation were divided into four categories (ineffectiveness, toxic adverse events, non-toxic reasons and remission); multivariate Cox proportional hazards modelling by potential confounders was used to analyse the HRs of treatment discontinuation. RESULTS: TNFi (HR=1.93, 95% CI: 1.69 to 2.19), CTLA4-Ig (HR=1.42, 95% CI: 1.20 to 1.67) and JAKi (HR=1.29, 95% CI: 1.03 to 1.63) showed a higher discontinuation rate due to ineffectiveness than aIL-6R. TNFi (HR=1.28, 95% CI: 1.05 to 1.56) and aIL-6R (HR=1.27, 95% CI: 1.03 to 1.57) showed a higher discontinuation rate due to toxic adverse events than CTLA4-Ig. Concomitant use of oral glucocorticoids (GCs) at baseline was associated with higher discontinuation rate due to ineffectiveness in TNFi (HR=1.24, 95% CI: 1.09 to 1.41), as well as toxic adverse events in JAKi (HR=2.30, 95% CI: 1.23 to 4.28) and TNFi (HR=1.29, 95%CI: 1.07 to 1.55). CONCLUSIONS: TNFi (HR=1.52, 95% CI: 1.37 to 1.68) and CTLA4-Ig (HR=1.14, 95% CI: 1.00 to 1.30) showed a higher overall drug discontinuation rate, excluding non-toxicity and remission, than aIL-6R.

Basic fibroblast growth factor promotes meniscus regeneration through the cultivation of synovial mesenchymal stem cells via the CXCL6-CXCR2 pathway.

OBJECTIVE: To investigate the efficacy of basic fibroblast growth factor (bFGF) in promoting meniscus regeneration by cultivating synovial mesenchymal stem cells (SMSCs) and to validate the underlying mechanisms. METHODS: Human SMSCs were collected from patients with osteoarthritis. Eight-week-old nude rats underwent hemi-meniscectomy, and SMSCs in pellet form, either with or without bFGF (1.0 × 106 cells per pellet), were implanted at the site of meniscus defects. Rats were divided into the control (no transplantation), FGF (-) (pellet without bFGF), and FGF (+) (pellet with bFGF) groups. Different examinations, including assessment of the regenerated meniscus area, histological scoring of the regenerated meniscus and cartilage, meniscus indentation test, and immunohistochemistry analysis, were performed at 4 and 8 weeks after surgery. RESULTS: Transplanted SMSCs adhered to the regenerative meniscus. Compared with the control group, the FGF (+) group had larger regenerated meniscus areas, superior histological scores of the meniscus and cartilage, and better meniscus mechanical properties. RNA sequencing of SMSCs revealed that the gene expression of chemokines that bind to CXCR2 was upregulated by bFGF. Furthermore, conditioned medium derived from SMSCs cultivated with bFGF exhibited enhanced cell migration, proliferation, and chondrogenic differentiation, which were specifically inhibited by CXCR2 or CXCL6 inhibitors. CONCLUSION: SMSCs cultured with bFGF promoted the expression of CXCL6. This mechanism may enhance cell migration, proliferation, and chondrogenic differentiation, thereby resulting in superior meniscus regeneration and cartilage preservation.

Early Resection of the Tibialis Anterior Tendon for Tendon Exposure After Total Ankle Arthroplasty to Prevent Deep Infection: A Report of Three Cases in Patients With Rheumatoid Arthritis.

Exposure of the tibialis anterior (TA) tendon with wound dehiscence after total ankle arthroplasty (TAA) with the anterior approach is a problematic complication, especially in rheumatoid arthritis (RA) patients. Once the TA tendon is exposed, the duration of wound healing is prolonged, and it could be a risk factor for deep infection. Thus, early resection of the TA tendon was evaluated for tendon exposure with wound dehiscence after TAA in RA patients. In this case report, three rheumatoid ankles that showed wound dehiscence with exposure of the TA tendon after TAA with the anterior approach are presented. Early resection of the TA tendon and debridement under local anesthesia were performed within two days after wound dehiscence. In all cases, wound healing was completed within two weeks after the treatment. Drop foot was not seen in any patients, and there was no difference between the pre and postoperative (1 year after TAA) range of dorsiflexion. Muscle strength for ankle dorsiflexion was also maintained. In conclusion, early resection of the TA tendon appears to be a useful option for undesirable tendon exposure with wound dehiscence to prevent deep infection and prolonged wound healing after total ankle arthroplasty in RA patients.

Early mobilization of dorsiflexion from 3 days after cemented total ankle arthroplasty with modified antero-lateral approach.

BACKGROUND: According to the conventional postoperative procedure after total ankle arthroplasty (TAA), mobilization is currently started after completion of wound healing. To investigate the possibility of expediting rehabilitation, this study evaluated the feasibility and safety of early mobilization of dorsiflexion after cemented TAA utilizing a modified antero-lateral approach. MATERIALS AND METHODS: This retrospective, observational study investigated 14 consecutive ankles that had received cemented TAA. Mobilization of dorsiflexion was started from 3 days after surgery. Postoperative wound complications including blister formation, eschar formation, wound dehiscence, peri-incisional decreased sensation were observed and recorded. Range of motion (ROM) of dorsiflexion/plantar flexion was measured. Patients also completed a self-administered foot evaluation questionnaire (SAFE-Q) and the scale of Japanese Society for Surgery of the Foot (JSSF) ankle/hindfoot score preoperatively and at final follow-up. RESULTS: No postoperative complications related to wound healing were observed. ROM for dorsiflexion, SAFE-Q score, and JSSF score improved significantly after TAA. CONCLUSION: Within this small number of cases, early mobilization of dorsiflexion from 3 days after cemented TAA was feasible and safe with the modified antero-lateral approach. Innovations in postoperative procedures for rehabilitation after TAA can be expected.

Modified scarf osteotomy with capsular interposition as salvage for resection or silicone implant arthroplasty in patients with rheumatoid arthritis. A report of three cases.

This study investigated modified scarf osteotomy as a salvage procedure after resection arthroplasty or silicone implant arthroplasty to preserve mobility of the first metatarsophalangeal (MTP) joint after hallux valgus surgery in patients with rheumatoid arthritis (RA). We investigated three feet with rheumatoid forefoot deformities that showed recurrence of forefoot deformity or breakage of the implant after resection or silicone implant arthroplasty in the first MTP joint. All feet were treated using modified scarf osteotomy with capsular interposition. All cases achieved obvious correction after modified scarf osteotomy despite resection of the first MTP joint and consequently showed both radiographic and clinical improvements. Modified scarf osteotomy offers potential as a definitive salvage procedure after resection arthroplasty or silicone implant arthroplasty for forefoot deformity in patients with RA, because the procedure can realign the first MTP joint obviously with preservation of the range of motion. Concomitant medial capsular interposition into the newly formed first MTP joint is also recommended where possible, to protect the edges of the proximal basal phalanx and distal first metatarsal and also to smoothen the motion of newly formed first MTP joint.

Add-on effectiveness of methotrexate or iguratimod in patients with rheumatoid arthritis exhibiting an inadequate response to Janus kinase inhibitors: The ANSWER cohort study.

OBJECTIVES: This multicenter, retrospective study evaluated the effectiveness of add-on methotrexate (MTX) or iguratimod (IGU) in patients with rheumatoid arthritis exhibiting an inadequate response to Janus kinase inhibitors (JAKis). METHODS: Forty-five patients were treated with new additional MTX (n = 22) or IGU (n = 23) and followed for 6 months. Patients' background is as follows: age, 59.2 years; disease activity score of 28 joints with C-reactive protein (DAS28-CRP), 3.4; clinical disease activity index, 15.7; biological disease-modifying antirheumatic drug (DMARD)-switched cases, 77.8%; first JAKi cases, 95.6%; and JAKi treatment: tofacitinib (n = 25), baricitinib (n = 17), upadacitinib (n = 2), and peficitinib (n = 1) for 9.6 months. RESULTS: Thirty-five patients continued the combination therapy for 6 months without a significant change in concomitant glucocorticoid or other conventional synthetic DMARDs. DAS28-CRP (MTX, 3.6 to 2.6, p < 0.05; IGU, 3.3 to 2.1, p < 0.001) and clinical disease activity index (MTX, 16.7 to 8.8, p < 0.05; IGU, 14.6 to 6.5, p < 0.01) improved significantly from baseline. Using the 2019 European League Against Rheumatism criteria, 45.4% (MTX) and 39.1% (IGU) achieved moderate or good response and 40.9% (MTX) and 39.1% (IGU) achieved American College of Rheumatology 20% improvement criteria. CONCLUSIONS: Adding MTX or IGU to inadequate responders of JAKi can be considered as a complementary treatment.

A novel anti-TNF-α drug ozoralizumab rapidly distributes to inflamed joint tissues in a mouse model of collagen induced arthritis.

In clinical studies, the next-generation anti-tumor necrosis factor-alpha (TNF-α) single domain antibody ozoralizumab showed high clinical efficacy shortly after the subcutaneous injection. To elucidate the mechanism underlying the rapid onset of the effects of ozoralizumab, we compared the biodistribution kinetics of ozoralizumab and adalimumab after subcutaneous injection in an animal model of arthritis. Alexa Fluor 680-labeled ozoralizumab and adalimumab were administered by subcutaneous injection once (2 mg/kg) at five weeks after induction of collagen-induced arthritis (CIA) in an animal arthritis model. The time-course of changes in the fluorescence intensities of the two compounds in the paws and serum were evaluated. The paws of the CIA mice were harvested at four and eight hours after the injection for fluorescence microscopy. Biofluorescence imaging revealed better distribution of ozoralizumab to the joint tissues than of adalimumab, as early as at four hours after the injection. Fluorescence microscopy revealed a greater fluorescence intensity of ozoralizumab in the joint tissues than that of adalimumab at eight hours after the injection. Ozoralizumab showed a significantly higher absorption rate constant as compared with adalimumab. These results indicate that ozoralizumab enters the systemic circulation more rapidly and is distributed to the target tissues earlier and at higher levels than conventional IgG antibodies. Our investigation provides new insight into the mechanism underlying the rapid onset of the effects of ozoralizumab in clinical practice.