Role of tear size and tendon degeneration for development of pain in rat models of rotator cuff tear.

BACKGROUND: Rotator cuff tear (RCT) is a frequent etiology of shoulder pain and disability; however, the triggers for the onset and aggravation of pain remain obscure. In this study, we established novel rat RCT models to examine the impact of tear size and tendon degeneration on pain. METHODS: Fifty-five adult male Sprague-Dawley rats were allocated into 4 study groups: large tear (L group, n = 10), small tear (S group, n = 15), small tear with scratching (S+ group n = 15), and sham surgery (Sham group, n = 15). Pain-related behaviors were evaluated by weight distribution of forelimbs during a 5-minute free gait using a dynamic weight-bearing apparatus at 2, 4, 6, and 8 weeks. Calcitonin gene-related peptide (CGRP) expressions in ipsilateral dorsal root ganglion (DRG) neurons of C4, C5, and C6 were evaluated at 4 and 8 weeks. The area of scar tissues around the torn tendon, infiltration of inflammatory cells, and severity of tendon degeneration (modified Bonar score) were histologically assessed at 4 and 8 weeks. Additionally, enzyme-linked immunosorbent assay (ELISA) was conducted to evaluate the levels of cyclooxygenase-2 (COX-2) and nerve growth factor (NGF) expression in torn tendons and surrounding tissues at 4 weeks. RESULTS: The weight distribution ratio (ipsilateral and contralateral side) was significantly decreased in the L and S+ group compared with its baseline and Sham group (P < .05), but the S group showed no significant difference compared with the Sham. The ratio of CGRP-immunoreactive neurons in the DRGs was significantly higher in the L and S+ groups than in the S and Sham groups. The histologic assessment indicated that scar tissue formation was more extensive in the L group than in the S and S+ groups. Still, there was no significant difference between the S and S+ groups. The modified Bonar score was considerably higher in the S+ group than in the S group. Furthermore, ELISA analysis demonstrated no significant disparity in COX-2 levels between the groups; however, NGF levels were substantially higher in the S+ group than in the S and Sham groups. CONCLUSION: The present study provides compelling evidence that large RCT is strongly associated with heightened pain severity in a rat model. Nevertheless, even a small tear can significantly aggravate pain when the torn tendon is degenerated. CGRP upregulation driven by peripheral NGF possibly played a pivotal role in the genesis and exacerbation of pain in small RCT.

Precision of the ultrasonography-integrated tibial extramedullary guide for total knee arthroplasty.

PURPOSE: Precise determination of the tibial mechanical axis in total knee arthroplasty (TKA) requires intraoperative identification of the talus center. We present the ultrasonography-integrated tibial extramedullary guide (USG) that enables real-time visualization of the talus. This study assesses the precision of USG compared to computer-assisted surgery (CAS) and validates the efficacy of USG. METHODS: We evaluated 58 patients (62 knees) who underwent primary TKA retrospectively, categorizing them into USG and CAS groups (31 each). We statistically analyzed demographic data, the preoperative alignment of the tibial plateau to the mechanical axis, the postoperative alignment of the tibial component to planned alignment on 3D-CT, pain visual analog scale, and WOMAC scores. Additionally, the frequency of postoperative outlier from planned alignment over 2° was statistically compared. RESULTS: No significant differences were observed in the preoperative data between the groups. The accuracy (mean deviation from the planned alignment) in both groups was not statistically different. However, in terms of the precision of coronal alignment, the USG group exhibited lower variance than the CAS group in the F-test (F value = 2.76, p = 0.023). Moreover, there were no postoperative deviations beyond 2 degrees in the USG group, in contrast to a 20% outlier frequency in the CAS group (p = 0.024). Concerning the precision of sagittal alignment (variance and deviations over 2°), no statistical differences were identified. CONCLUSION: The USG demonstrated higher precision in the tibial coronal plane than CAS in coronal alignment. Direct identification of the individual talus may enhance precision.

Arthroscopic labral repair combined with less invasive open-shelf acetabuloplasty for patients with developmental dysplasia of the hip.

Hip arthroscopy has become widely used for intra-articular lesions, such as labral tears and femoral acetabular impingement. However, its use in patients with developmental dysplasia of the hip (DDH) has been controversial and has historically demonstrated mixed results, as acetabular dysplasia may cause instability due to insufficient bony coverage of the femoral head, thus causing excessive stress on the repaired labrum and cartilage. We devised a combined hip arthroscopic labral repair and a less invasive open-shelf procedure using a small skin incision as an anterolateral portal in hip arthroscopy. This novel procedure may improve the stability of the repaired labrum with a bony covering in a minimally invasive manner. Moreover, the shelf procedure can be performed under direct vision in a comparatively safe and precise manner. In total, 13 hips with DDH underwent the procedure for labral tears. All patients were females, with a mean age of 30 years. The mean follow-up period was 33 months. The mean Harris hip score improved from 74.2 to 93.6, and Oxford Hip score improved from 32.4 to 19.3. According to the Tönnis classification, the grade of arthritis preoperatively was grade 0 for nine hips and grade I for four hips. No radiographic progression of osteoarthritis was observed. It is possible that this novel procedure could be an effective treatment for labral tears with DDH and may prevent the early onset of secondary osteoarthritis. In this technical tip, we describe hip arthroscopic labral repair combined with a less invasive open-shelf acetabuloplasty in further detail.

Chronic postsurgical pain after total knee arthroplasty: A prospective cohort study in Japanese population.

OBJECTIVES: To elucidate the prevalence and risk factors of chronic postsurgical pain (CPSP) after primary total knee arthroplasty (TKA) in Japanese population. METHODS: Consecutive patients undergoing primary TKA in a Japanese tertiary hospital (211 knees) were assessed. CPSP after TKA was defined as moderate to severe pain (VAS >30 mm), either at rest or during walking, one year after surgery. Clinical and radiographic data were compared between CPSP and non-CPSP groups and multivariate logistic regression was used to identify predictors of CPSP. RESULTS: The prevalence of CPSP was 8.8%. CPSP group showed significantly higher preoperative WOMAC subscales (pain, function and stiffness), higher rate of postoperative coronal malalignment (femorotibial angle >178° or <170°) and larger varus angle of tibial component compared with non-CPSP group. Logistic regression analysis revealed that preoperative higher WOMAC pain and postoperative coronal malalignment were independent risk factors of CPSP. In a subgroup analysis of patients with well-aligned TKA, preoperative pain VAS at rest was the only risk factor of CPSP. CONCLUSION: Preoperative severe pain and postoperative coronal malalignment were independent risk factors of CPSP after TKA. Preoperative pain management in patients with severe pain and good coronal alignment after TKA possibly minimize the development of CPSP.

Additional benefit of local infiltration of analgesia to femoral nerve block in total knee arthroplasty: double-blind randomized control study.

PURPOSE: Multimodal analgesia has become an important concept in current pain management following total knee arthroplasty (TKA). However, controversy remains over what is the most accepted combination. In this study, the additional benefits of local infiltration of analgesia to femoral nerve block were evaluated. METHODS: Forty patients were randomly allocated into a combined local infiltration of analgesia and femoral nerve block or femoral nerve block alone group. In the former, analgesic drugs consisting of ropivacaine and dexamethasone were injected into the peri-articular tissues, while the same amount of saline was injected into the femoral nerve block group. The primary outcome measure was the total amount of fentanyl consumption by the patient-controlled analgesia pump during the 48-h post-operative period. RESULTS: A combination of local infiltration of analgesia and femoral nerve block had less total fentanyl consumption and a larger knee ROM at post-operative day 2 than femoral nerve block alone (p < 0.05). C-reactive protein levels in the combined treatment group were significantly lower than the femoral nerve block group at post-operative day 3 (p < 0.01). There was no difference between the two groups, post-operatively, on the visual analogue scale for pain at rest or while walking, quadriceps strength, timed up and go test, circumference of thigh, Knee Society Score, and Western Ontario and McMaster Universities Osteoarthritis Index. CONCLUSION: The addition of local infiltration of analgesia to femoral nerve block promoted post-operative pain relief and the recovery of knee ROM in the early post-operative period. This combination is an effective method for post-operative pain management after TKA. LEVEL OF EVIDENCE: Randomized controlled trial, Level I.

Association between Falls and Balance among Inpatients with Schizophrenia: A Preliminary Prospective Cohort Study.

Falls are adverse events affecting psychiatric inpatients that can lead to external injuries, fractures, and death. However, none have attempted to examine fall-related factors, particularly focused on balance, specifically among inpatients with schizophrenia. The present preliminary study aimed to assess the association between falls and balance in patients with schizophrenia. The authors performed baseline assessments of background factors, postural sway, and maximum step length in 120 patients with schizophrenia hospitalized in the psychiatric ward. A prospective 3-month follow-up was conducted, and participants were divided into a fall or non-fall group according to their history of falls during the follow-up. Variance among individual variables was compared between the fall group and non-fall group using the t-test, Mann-Whitney U test, and chi-square test. A total of 16 participants experienced falls in the 3-month follow-up period (13.3%). Comparative factor analysis revealed significant differences between the fall and non-fall groups in terms of the presence or absence of falls within 3 months before follow-up (p = 0.002) and Romberg quotients for sway length (p = 0.02). These findings suggest that fall history could be considered a predictor of future falls, which could help with fall prevention, and that assessment of visual contribution to postural control using the Romberg quotient could play an important role in fall prevention.

Less deep vein thrombosis due to transcutaneous fibular nerve stimulation in total knee arthroplasty: a randomized controlled trial.

PURPOSE: It has been known for years that deep vein thrombi (DVT) start to develop during total joint arthroplasty. Previously, we reported effective prevention of venous stasis by transcutaneous electrical nerve stimulation (TENS). It is hypothesized that TENS might be a thromboprophylactic tool for the limb undergoing surgery. The purpose of this study is to clarify the clinical efficacy and safety of TENS in patients during total knee arthroplasty (TKA). METHODS: Ninety patients undergoing primary TKA were involved and randomly allocated to the TENS or control group. In the TENS group, electrical stimulation of the common fibular nerve, which produced a brisk dorsiflexion of the ankle, was performed for the operated leg during surgery. In the control group, no electrical stimulation was applied. Serum D-dimer and soluble fibrin monomer complex (SFMC) levels were measured before surgery, immediately after surgery, and post-operative day (POD) 1. Ultrasonography was performed on POD 1. RESULTS: Immediately after surgery, D-dimer and SFMC levels of each group were significantly lower in the TENS group compared with control (p < 0.05). The incidence of DVT was 11 % (five cases) in the TENS group while 31 % (14 cases) in control (p = 0.02). There were no adverse effects related to TENS. CONCLUSIONS: TENS during TKA showed significant effects on preventing DVT. Sustaining muscle pump activation during surgery prevented not only venous stasis, but also hypercoagulability of blood. Intraoperative TENS is a safe and novel strategy against early post-operative thromboembolism, which is difficult to be completed through existing prophylaxis after total joint arthroplasty. LEVEL OF EVIDENCE: Randomized controlled trial, Level I.

Less invasive modified Spitzy shelf procedure for patients with dysplasia of the hip.

The shelf procedure for developmental dysplasia of the hip (DDH) is a simpler technique compared with periarticular acetabular osteotomies. However, the most commonly used approach involves the exposure of a large section of the outer iliac surface via a long skin incision and is relatively invasive. We have developed a mini one-incision technique for shelf procedure using bioabsorbable material, based on a modified Spitzy method. In the present report, we describe this procedure and outcomes. For the procedure, the patients are positioned in the lateral position and a 6-8-cm skin incision is made. The interval between the gluteus medius and the tensor fascia lata is developed without any muscle splitting. Thereafter, image intensification is used for accurate positioning of a slot for the new shelf, and a bone graft for the new shelf is obtained from the internal cortex of the iliac wing. The patient is then positioned with the hip in flexion; through the same sliding skin incision, the bone graft is impacted into the slot, and bioabsorbable screws or plates are implanted to cover and stabilise the new shelf. Cancellous bone chips are packed into the triangular space surrounded by the outer iliac surface, the new shelf, and the bioabsorbable screws or plate. We performed this procedure in 9 patients (12 hips). No progression of osteoarthritis was observed during the follow-up period (mean 28 months). The advantages of this procedure include the small, single, skin incision and minimal removal of the gluteus medius from the outer iliac surface. Based on our results, we believe that this procedure could be effective for the treatment of DDH.

Effects of two different intensities of transcutaneous electrical nerve stimulation on pain thresholds of contralateral muscles in healthy subjects.

[Purpose] This study aimed to investigate the differential effects of high-intensity and low-intensity transcutaneous electrical nerve stimulation on the contralateral side on the pain threshold in healthy subjects. [Subjects and Methods] Twenty-five healthy adults, volunteers received two intensity levels (motor-level, 1.5 times the muscle motor threshold; sensory-level, sensory threshold of the common peroneal nerve), for 30 s on separate days. Pressure pain threshold was recorded on the contralateral tibialis anterior and deltoid muscle before, during, and after stimulation. [Results] Motor-level stimulation significantly increased the pressure pain threshold at both muscle sites, while effects of sensory-level stimulation on pressure pain thresholds were significant only at the deltoid site. The percent change in pressure pain thresholds at both sites was significantly higher during motor-level stimulation. [Conclusion] Motor-level stimulation, applied unilaterally to one leg, produced immediate contralateral diffuse and segmental analgesic effects. This may be of therapeutic benefit in patients for whom transcutaneous electrical nerve stimulation cannot be directly used at the painful site.

The dorsal pedis artery as a new distal landmark for extramedullary tibial alignment in total knee arthroplasty.

PURPOSE: It is better to use multiple anatomical landmarks to reduce errors in component alignment in total knee arthroplasty. Therefore, it is worthwhile to find a new landmark that can be used as an addition to conventional ones. Herein, we assessed the dorsal pedis artery as a new distal landmark for extramedullary tibial alignment. METHODS: Fifty-two ankles in patients undergoing total knee arthroplasty and 10 ankles in normal controls were included. Color Doppler ultrasonography was used to locate the dorsal pedis artery at the level of the ankle joint. Conventional landmarks, including the tibialis anterior tendon, the extensor hallucis longus tendon, the extensor digitorum longus tendon, and the malleolar centre, were also located on ultrasound images. The distances between the ankle centre and each landmark were measured and compared. RESULTS: The dorsal pedis artery was absent in 2 patients and impalpable but visible with ultrasonography in other 2 patients. The dorsal pedis artery was located anatomically closest to the ankle centre in patients (0.4 ± 3.4 mm lateral). Statistical analysis showed that the dorsal pedis artery, the extensor hallucis longus tendon, and the malleolar centre were located significantly closer to the ankle centre comparing with the extensor digitorum longus tendon and the tibialis anterior tendon in both patients and controls (p < 0.001). CONCLUSIONS: As long as the dorsal pedis artery exists, it can be used as an addition to the conventional landmarks in total knee arthroplasty. Using this new landmark will help reduce errors in coronal plane alignment of tibial component. LEVEL OF EVIDENCE: II.

Effects of dexamethasone on local infiltration analgesia in total knee arthroplasty: a randomized controlled trial.

PURPOSE: Intraoperative local infiltration analgesia has gained increasing popularity in joint replacement surgery. Because there is considerable variation among drug combinations, analgesic effects of each drug are not well understood. The purpose of this study was to clarify the efficacy of the addition of steroid to local anaesthetics in local infiltration analgesia during total knee arthroplasty. METHODS: Forty patients were randomly allocated to the steroid or control group. Patients in the steroid group received peri-articular injection of ropivacaine, dexamethasone and isepamicin, while dexamethasone was omitted from the analgesic mixture in the control group. Primary outcome was pain severity at rest using 100 mm visual analogue scale. RESULTS: Pain severity in the steroid group was lower than control group and there were significant differences between groups at post-operative day 1 and 3. Reduction in post-operative pain was associated with a decrease in serum C-reactive protein and interleukin 6 in drainage fluid. The number of patients who were able to perform straight leg raise within post-operative day 2 was 15/20 in the steroid group, which was significantly higher than the control group 5/20. CONCLUSION: Adding steroid to local anaesthetics in local infiltration analgesia reduced inflammation both locally and systemically, resulting in significant early pain relief and rapid recovery in total knee arthroplasty.

Improving tibial component coronal alignment using clearly defined anatomical structures in total knee arthroplasty.

Several authors recently proposed to use clearly defined anatomical structures for extramedullary tibial alignment in total knee replacement, instead of using the intermalleolar center. The purpose of this study was to evaluate the benefits of using the dorsalis pedis artery and the anterior tibial crest as distal landmarks. Postoperative radiographs in 195 knees (98 in the control and 97 in the landmark group) were evaluated. The mean coronal alignment of the tibial component was 89.7 degrees +/- 2.1 degrees in the control group and 90.0 degrees +/- 1.3 degrees in the landmark group. Although there was no significant difference, the proportion of radiological outliers was significantly reduced in the landmark group compared to the control group (6.2% vs 27.6% in > 2 degrees outliers; p < 0.0001, 1.0% vs 10.2% in > 3 degrees outliers; p = 0.01). In order to achieve accurate coronal alignment of the tibial component, it appears better to use multiple clear anatomical landmarks such as the dorsal pedis artery and the anterior tibial crest rather than using only the intermalleolar center.

The effect of postmenopausal osteoporosis on subchondral bone pathology in a rat model of knee osteoarthritis.

This study aimed to investigate the additional effect of ovariectomy-induced osteoporosis (OP) on the pathology of knee osteoarthritis (OA) in a rat meniscectomized model, particularly focusing on subchondral bone changes and pain behaviour. Rats were divided into four groups, sham, OP, OA, OP plus OA, and assessed for histology, osteoclast activity, subchondral bone microstructure, and pain-related behaviour. Rats with OP plus OA had significantly increased calcified cartilage and subchondral bone damage scores, increased densities of subchondral osteoclasts in the weight-bearing area, and more porous subchondral trabecular bone compared with rats with OA. Loss of tidemark integrity was observed most frequently in rats with OP plus OA. The density of subchondral osteoclasts correlated with the calcified cartilage and subchondral bone damage score in rats with OA (OA and OP plus OA). No significant differences in the receptor activator of nuclear factor-kappa B ligand (RANKL)/osteoprotegerin (OPG) expression ratio in subchondral bone and pain-related behavioural tests were observed between rats with OA and rats with OP plus OA. In rats with OA, coexisting OP potentially aggravated OA pathology mainly in calcified cartilage and subchondral trabecular bone by increasing subchondral osteoclast activity.

Association between infrapatellar fat pad ultrasound elasticity and anterior knee pain in patients with knee osteoarthritis.

This study investigates whether infrapatellar fat pad (IPFP) elasticity is associated with anterior knee pain in patients with knee osteoarthritis (KOA). The IPFP elasticity of 97 patients with KOA (Kellgren and Lawrence [KL] grades of the femorotibial and patellofemoral joints ≥ 2 and ≤ 2, respectively), aged 46-86 years, was evaluated via shear wave speed using ultrasound elastography. The patients were divided into two groups according to the presence or absence of anterior knee pain. Univariate analyses were used to compare patient age, sex, femorotibial KL grade, magnetic resonance imaging findings (Hoffa, effusion synovitis, bone marrow lesion scores, and IPFP size), and IPFP elasticity between the groups. Multivariate logistic regression analyses were subsequently performed using selected explanatory variables. IPFP elasticity was found to be associated with anterior knee pain in the univariate (p = 0.007) and multivariate (odds ratio: 61.12, 95% CI 1.95-1920.66; p = 0.019) analyses. Anterior knee pain is strongly associated with stiffer IPFPs regardless of the femorotibial KL grade, suggesting that ultrasound elastography is useful for the diagnosis of painful IPFP in patients with KOA.

Associations of serum leptin levels with intra-articular inflammatory cytokine levels in acute arthritic and nonarthritic knees of mice.

BACKGROUND: The roles of serum leptin in knee joint inflammation are unclear. The objective of this study was to identify any associations of serum leptin level with intra-articular inflammatory cytokine levels in acute arthritic and nonarthritic knees of mice. METHODS: Acute arthritis was induced by intra-articular injection of 2% carrageenan. Three groups (leptin-deficient ob/ob, wild-type (WT) and high-fat diet (HFD)-fed WT) were made. Serum leptin and inflammatory cytokines in the infrapatellar fat pad and synovium were measured before and 24 hr after injection. Affected knee joints were excised for histology 24 hr after injection. RESULTS: The HFD-WT group had significantly higher serum leptin than the ob/ob and WT groups before and after carrageenan injection. The HFD-WT group had significantly higher IL-1? and IL-6 in the infrapatellar fat pad and synovium than ob/ob and WT before injection but significantly lower IL-1?, IL-6 and TNF-? than the ob/ob group at 24 hr. CONCLUSIONS: Hyperleptinemia induced by a HFD is involved in low-grade intra-articular inflammation in nonarthritic knee joints. In contrast, leptin deficiency causes excessive intra-articular inflammation in carrageenan-induced acute arthritis. Leptin alleviates acute arthritis, while chronic hyperleptinemia is involved in low-grade inflammation in normal knee joints. J. Med. Invest. 70 : 54-59, February, 2023.

Association Between Power Doppler Ultrasound Signals and Chronic Pain After Total Knee Arthroplasty: A Cross-Sectional Explorative Study.

Purpose: Some patients experience chronic postsurgical pain (CPSP) after total knee arthroplasty (TKA) despite the absence of clinical or radiographic abnormalities. Postoperative synovitis as a cause of CPSP after TKA has received limited research attention. This study aimed to investigate the relationship between synovitis after TKA and CPSP. Patients and Methods: A total of 111 knees of 85 patients, with at least 1-year post-TKA follow-up, were assessed retrospectively and cross-sectionally. Power Doppler (PD) ultrasonography was used to detect the synovial hypervascularity associated with synovitis. The knee joint was divided into 15 areas, and PD signals were graded semi-quantitatively (0-3) in each area, the sum of which was defined as the total PD score. Clinical information regarding CPSP, including the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscales, was recorded. The relationship between pain and PD ultrasonography findings was accessed. Patients were divided into two groups (CPSP+ and CPSP- groups) based on pain severity. Clinical information, including PD ultrasonography findings and other possible causes, was compared between the groups. Results: The WOMAC pain subscale was significantly correlated with the total PD score and maximum PD grade (r=0.3977, p<0.0001; r=0.2797, p=0.0029; respectively). The CPSP+ group had a significantly higher maximum PD grade and total PD score than the CPSP- group (median [interquartile range]: 2 [1, 2] vs 1 [1, 2], p=0.0001; 6 [2, 11] vs 2 [1, 4], p=0.0002; respectively). Multiple and logistic regression analyses showed that the total PD score was an independent factor for the WOMAC pain subscale (ß=0.3822, 95% confidence interval [CI]=0.1460, 0.6184, p=0.00176) and CPSP (odds ratio=1.19, 95% CI=1.01, 1.41, p=0.0424). Conclusion: This study indicated a possible association between the total PD score and chronic pain after TKA; however, further studies are needed to corroborate these findings.

A Novel Rat Model to Study Postsurgical Pain After Joint Replacement Surgery.

Purpose: The mechanisms underlying chronic postsurgical pain after joint replacement (JR) are complex, and it has been suggested that chronic postsurgical pain can develop as a result of inadequate acute pain management. Few studies have addressed acute pain after JR using specific animal models. This study aimed to develop a novel JR model focused on postsurgical pain assessment and the time course of pain recovery. Materials and Methods: Rats were allocated to the following three groups: sham (joint exposure), joint destruction (JD; resection of the femoral head), and JR (femoral head replacement using an originally developed implant). The time course of postsurgical pain behavior was measured using a dynamic weight-bearing apparatus, along with radiological assessments. The expression of calcitonin gene-related peptide-immunoreactive (CGRP-IR) neurons in the dorsal root ganglion (DRG) was evaluated by immunohistochemistry on days 28 and 42. Results: The ratio of weight-bearing distribution in the JR group gradually recovered from day 14 and reached the same level as that in the sham group on day 42, which was significantly greater than that in the JD group after day 7 (p<0.05). Radiologically, no significant issues were found, except for transient central migration of the implant in the JR group. The percentage of CGRP-IR DRG neurons in the JR group was significantly lower than that in the JD group on day 28 (mean, 37.4 vs 58.1%, p<0.05) and day 42 (mean, 32.3 vs 50.0%, p<0.05). Conclusion: Our novel JR model presented acute postsurgical pain behavior that was successfully recovered to the baseline level at day 42 after surgery. Difference of the pain manifestation between the JR and JD groups could be supported by the expression of CGRP-IR in DRG neurons. This model is the first step toward understanding detailed mechanisms of post-JR pain.

Association of subchondral bone marrow lesion localization with weight-bearing pain in people with knee osteoarthritis: data from the Osteoarthritis Initiative.

BACKGROUND: Subchondral bone marrow lesions (BMLs) detected on MRI in knee osteoarthritis (OA) are associated with knee pain. The prevalence and progression of subchondral BMLs are increased by mechanical knee load. However, associations of subchondral BML location with weight-bearing knee pain are currently unknown. In this study, we aim to demonstrate associations of subchondral BML location and size with weight-bearing knee pain in knee OA. METHODS: We analyzed 1412 and 582 varus knees from cross-sectional and longitudinal Osteoarthritis Initiative datasets, respectively. BML scores were semi-quantitatively analyzed with the MRI Osteoarthritis Knee Score for 4 subchondral regions (median and lateral femorotibial, medial and lateral patellofemoral) and subspinous region. Weight-bearing and non-weight-bearing pain scores were derived from WOMAC pain items. Correlation and negative binomial regression models were used for analysis of associations between the BML scores and pain at baseline and changes in the BML scores and changes in pain after 24-month follow-up. RESULTS: Greater BML scores at medial femorotibial and lateral patellofemoral compartments were associated with greater weight-bearing pain scores, and statistical significance was retained after adjusting for BML scores at the other 4 joint compartments and other OA features, as well as for non-weight-bearing pain, age, sex, and body mass index (BMI) (medial femorotibial; B = 0.08, p = 0.02. patellofemoral; B = 0.13, p = 0.01). Subanalysis revealed that greater medial femorotibial BML scores were associated with greater pain on walking and standing (B = 0.11, p = 0.01, and B = 0.10, p = 0.04, respectively). Lateral patellofemoral BML scores were associated with pain on climbing, respectively (B = 0.14, p = 0.02). Increases or decreases over 24 months in BML score in the medial femorotibial compartment were significantly associated with increases or decreases in weight-bearing pain severity after adjusting for non-weight-bearing pain, age, sex, baseline weight-bearing pain, BMI, and BML at the other 4 joint compartments (B = 0.10, p = 0.01). CONCLUSIONS: Subchondral BML size at the medial femorotibial joint compartment was specifically associated with the severity and the change in weight-bearing pain, independent of non-weight-bearing pain, in knee OA. Specific associations of weight-bearing pain with subchondral BMLs in weight-bearing compartments of the knee indicate that BMLs in subchondral bone contribute to biomechanically induced OA pain.

Comparison of Predisposing Factors Between Pain on Walking and Pain at Rest in Patients with Knee Osteoarthritis.

PURPOSE: Patients with knee osteoarthritis (OA) complain of various types of pain, divided into two main categories: pain on movement and pain at rest. A thorough understanding of pain is essential for managing knee OA; however, few studies have investigated the mechanisms underlying the two different types of pain. This study aimed to clarify the predisposing factors for pain in patients with knee OA with a focus on differences between pain on walking and pain at rest. PATIENTS AND METHODS: This study involved 93 patients, aged 44-90 years, with knee OA, including 74 women. We assessed demographic variables (sex, age, body mass index [BMI], side), visual analogue scale (VAS) score on walking, VAS score at rest, Kellgren and Lawrence (KL) grade on radiograph, synovitis score and bone marrow lesion (BML) score on magnetic resonance imaging, and pressure pain threshold (PPT), and used univariate and multiple regression analyses to investigate factors predisposing patients to pain at rest or pain on walking. RESULTS: In the univariate analyses, we found significant correlations between VAS score on walking and BMI (r=0.31, p<0.01), KL grade (r=0.40, p<0.01), synovitis score (r=0.26, p=0.01), and BML score (r=0.36, p<0.01), whereas VAS score at rest correlated with PPT (r=-0.23, p=0.02) and BMI (r= 0.26, p=0.01). Multiple regression analysis showed that significant explanatory factors for VAS score on walking were BMI (ß=0.22, p=0.03) and KL grade (ß=0.27, p=0.03). By contrast, PPT was the only significant explanatory factor for VAS score at rest (ß=-0.27, p=0.01). CONCLUSION: Predisposing factors were significantly different between pain on walking and pain at rest, indicating that different pain mechanisms exist in the two types of pain. Pain on walking was more strongly associated with mechanical and structural factors, while pain at rest was associated with mechanical hyperalgesia of the knee. CLINICAL REGISTRATION: University Hospital Medical Information Network Clinical Trials Registration number; 000041190.

Promising Effect of Visually-Assisted Motor Imagery Against Arthrogenic Muscle Inhibition - A Human Experimental Pain Study.

PURPOSE: Clinically, arthrogenic muscle inhibition (AMI) has a negative impact on functional recovery in musculoskeletal disorders. One possible technique to relieve AMI is motor imagery, which is widely used in neurological rehabilitation to enhance motor neuron excitability. The purpose of this study was to verify the efficacy of visually-assisted motor imagery against AMI using a human experimental pain model. METHODS: Ten healthy volunteers were included. Experimental ankle pain was induced by hypertonic saline infusion into unilateral Kager's fat pad. Isotonic saline was used as control. Subjects were instructed to imagine while watching a movie in which repetitive motion of their own ankle or fingers was shown. H-reflex normalized by the motor response (H/M ratio) on soleus muscle, maximal voluntary contraction (MVC) force of ankle flexion, and contractile activities of the calf muscles during MVC were recorded at baseline, pre-intervention, post-intervention, and 10 minutes after the pain had subsided. RESULTS: Hypertonic saline produced continuous and constant peri-ankle pain (VAS peak [median]= 6.7 [2.1-8.4] cm) compared to isotonic saline (0 [0-0.8] cm). In response to pain, there were significant decreases in the H/M ratio, MVC and contractile activities (P<0.01), all of which were successfully reversed after the ankle motion imagery. In contrast, no significant changes were observed with the finger motion imagery. CONCLUSION: Visually-assisted motor imagery improved the pain-induced AMI. Motor imagery of the painful joint itself would efficiently work for relieving AMI. This investigation possibly shows the potential of a novel and versatile approach against AMI for patients with musculoskeletal pain.