Effect of Knee Hyperextension on Femoral Cartilage Thickness in Stroke Patients

OBJECTIVE

Knee hyperextension is one of the most common compensatory mechanisms in stroke patients. The first aim of the study was to measure knee hyperextension and femoral cartilage thickness in stroke patients. The second aim was to compare the femoral cartilage thickness of the paretic and nonparetic limbs in stroke patients with and without knee hyperextension.

DESIGN

Forty stroke patients were included in the study. The patients were divided into two groups according to the presence of knee hyperextension based on kinematic analyses performed during walking with a three-dimensional motion analysis system. The medial femoral cartilage, lateral femoral cartilage, and intercondylar cartilage thicknesses of the paretic and nonparetic sides of the patients were measured by ultrasonography.

RESULTS

In the study group, medial femoral cartilage, intercondylar, and lateral femoral cartilage thicknesses were less on the paretic side than on the nonparetic side, while the femoral cartilage thicknesses on the paretic and nonparetic sides were similar in the control group. Paretic side medial femoral cartilage and intercondylar thicknesses were less in the study group compared with the control group, and lateral femoral cartilage thickness was similar between the two groups.

CONCLUSIONS

Knee hyperextension during walking causes femoral cartilage degeneration in stroke patients.Clinical Trial code: NCT05513157.

Chondrocyte Hypertrophy in Osteoarthritis: Mechanistic Studies and Models for the Identification of New Therapeutic Strategies

Articular cartilage shows limited self-healing ability owing to its low cellularity and avascularity. Untreated cartilage defects display an increased propensity to degenerate, leading to osteoarthritis (OA). During OA progression, articular chondrocytes are subjected to significant alterations in gene expression and phenotype, including a shift towards a hypertrophic-like state (with the expression of collagen type X, matrix metalloproteinases-13, and alkaline phosphatase) analogous to what eventuates during endochondral ossification. Present OA management strategies focus, however, exclusively on cartilage inflammation and degradation. A better understanding of the hypertrophic chondrocyte phenotype in OA might give new insights into its pathogenesis, suggesting potential disease-modifying therapeutic approaches. Recent developments in the field of cellular/molecular biology and tissue engineering proceeded in the direction of contrasting the onset of this hypertrophic phenotype, but knowledge gaps in the cause-effect of these processes are still present. In this review we will highlight the possible advantages and drawbacks of using this approach as a therapeutic strategy while focusing on the experimental models necessary for a better understanding of the phenomenon. Specifically, we will discuss in brief the cellular signaling pathways associated with the onset of a hypertrophic phenotype in chondrocytes during the progression of OA and will analyze in depth the advantages and disadvantages of various models that have been used to mimic it. Afterwards, we will present the strategies developed and proposed to impede chondrocyte hypertrophy and cartilage matrix mineralization/calcification. Finally, we will examine the future perspectives of OA therapeutic strategies.

Bone replaces unloaded articular cartilage during knee immobilization. A longitudinal study in the rat

BACKGROUND

Joint immobility results in deleterious changes such as capsule shortening, bone loss and articular cartilage damage. Immobilization of rat knees in flexion for 32 weeks resulted in the distinctive feature of well-established replacement of articular cartilage by bone. Determining the time of onset of bone replacement is critical for the prevention of this likely irreversible complication of joint immobilization.

OBJECTIVES

To determine the onset and progression of bone replacement in the anterior tibial articular cartilage following knee immobilization in flexion.

METHODS

One hundred forty-nine adult male Sprague-Dawley rats were used. The experimental groups had one knee immobilized at 135°of flexion for durations of 2, 4, 8, 16 or 32 weeks and were compared to age-matched controls. The knees were evaluated histologically for the presence and cross-sectional area of bone within the articular cartilage of the tibia. Distance between the anterior aspect of the tibia and intact articular cartilage and cross-sectional bone area of the tibial epiphysis were also measured.

RESULT

Bone replacement in the articular cartilage was observed in 14%, 75%, 95%, 100% and 100% of knees after 2, 4, 8, 16 and 32 weeks of immobilization, respectively. No bone replacement was seen in the control knees. The mean area of bone replacement increased from 0.004 ± 0.007 mm² after 2 weeks to 0.041 ± 0.036 mm²; 0.085 ± 0.077 mm²; 0.092 ± 0.056 mm² and 0.107 ± 0.051 mm² after 4, 8, 16 and 32 weeks of immobilization, respectively, (p < 0.001) largely restricted to the anterior tibial articular cartilage. Mean distance to intact articular cartilage increased from 0.89 ± 0.69 mm at 2 weeks to 1.10 ± 0.35 mm; 1.65 ± 0.77 mm; 1.48 ± 0.63 mm; and 1.78 ± 0.58 mm after 4, 8, 16 and 32 weeks of immobilization, respectively (p = 0.001). Epiphyseal bone cross-sectional area was significantly reduced following 4, 8, and 16 weeks of immobilization compare to controls (all 3 p < 0.05).

CONCLUSION

Knee immobilization in flexion resulted in bone replacement in the anterior tibial articular cartilage that began after 2 weeks and was prevalent after 4 weeks of immobilization. The bone replacement progressed in an anterior-to-posterior direction and stopped at the area of contact between tibia and femur. These findings stress the importance of mobility to maintain joint health.

Joint hemorrhage accelerates cartilage degeneration in a rat immobilized knee model

Background

Joint hemorrhage is caused by trauma, ligament reconstruction surgery, and bleeding disorders such as hemophilia. Recurrence of hemorrhage in the joint space induces hemosiderotic synovitis and oxidative stress, resulting in both articular cartilage degeneration and arthropathy. Joint immobilization is a common treatment option for articular fractures accompanied by joint hemorrhage. Although joint hemorrhage has negative effects on the articular cartilage, there is no consensus on whether a reduction in joint hemorrhage would effectively prevent articular cartilage degeneration. The purpose of this study was to investigate the effect of joint hemorrhage combined with joint immobilization on articular cartilage degeneration in a rat immobilized knee model.

Methods

The knee joints of adult male rats were immobilized at the flexion using an internal fixator from 3 days to 8 weeks. The rats were randomly divided into the following groups: immobilized blood injection (Im-B) and immobilized-normal saline injection (Im-NS) groups. The cartilage was evaluated in two areas (contact and non-contact areas). The cartilage was used to assess chondrocyte count, Modified Mankin score, and cartilage thickness. The total RNA was extracted from the cartilage in both areas, and the expression of metalloproteinase (MMP)-8, MMP-13, interleukin (IL)-1β, and tumor necrosis factor (TNF)-α was measured by quantitative real-time polymerase chain reaction.

Results

The number of chondrocytes in the Im-B group significantly decreased in both areas, compared with that in the Im-NS group. Modified Mankin score from 4 to 8 weeks of the Im-B group was significantly higher than that of the Im-NS group only in the contact area. The expression of MMP-8 and MMP-13 from 2 to 4 weeks and TNF-α from 2 to 8 weeks significantly increased in the Im-B group compared with those in the Im-NS group, but there was no significant difference in IL-1β expression.

Conclusions

The results showed that joint hemorrhage exacerbated immobilization-induced articular cartilage degeneration. Drainage of a joint hemorrhage or avoidance of loading may help prevent cartilage degeneration during joint immobilization with a hemorrhage.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-020-03795-0.

Electroacupuncture alleviates cartilage degradation: Improvement in cartilage biomechanics via pain relief and potentiation of muscle function in a rabbit model of knee osteoarthritis

Knee osteoarthritis (KOA) is a chronic degenerative joint disorder characterized by loss of articular cartilage and progressive deterioration, leading to pain and functional limitation. Abnormal biomechanics play a core role in the onset and development of KOA. The aim of this study was to explore whether electroacupuncture (EA) may relieve pain and adjust the biomechanical properties of the extensor-flexor muscles to improve abnormal joint loading, thus alleviating the degradation of cartilage in a rabbit model of KOA. Firstly, a KOA model was induced by immobilization for 6 weeks. Then, different interventions (EA and celecoxib) were applied for 4 weeks. The levels of pain and disability were assessed using the Lequesne MG index. Muscle function, including function of the rectus femoris and biceps femoris, was tested through hematoxylin-eosin staining (HE staining) and use of a microforce tension-torsion instrument. The cartilage was tested using nanoindentation, Safranin O-Fast Green staining, confocal laser scanning microscopy (immunofluorescence), immunohistochemistry and the enzyme-linked immunosorbent assay (ELISA). Finally, we found that EA and celecoxib resulted in lower behavioral and pain scores than the model group. In addition, it improved the function of muscles. Furthermore, those treatments alleviated the rate of cartilage degradation, manifested as increased loss factor without statistical difference and a significant reduction in the Mankin score. This promoted the metabolism of type II collagen in the cartilage layer and drastically reduced the expression of CTX-II in the synovial fluid and peripheral serum. Concisely, EA promotes pain limitation and ameliorates muscular atrophy-induced inappropriate biomechanical loading on the articular cartilage through pain relief and potentiation of muscle function, thus improving cartilage viscoelasticity, as demonstrated by the retarded degradation of type II collagen in our KOA model.

Re-examining osteoarthritis therapy from a developmental biologist's perspective

Osteoarthritis is the most prevalent musculoskeletal disorder and one for which there is no disease modifying therapy available at present. Our current understanding of the disease mechanism of osteoarthritis is limited owing to a lacuna of knowledge about the development and maintenance of articular cartilage that is affected during osteoarthritis. All current therapeutic strategies aim at countering inflammation which though mitigates pain but does not arrest the progressive degeneration of articular cartilage. During osteoarthritis, articular cartilage expresses markers for transient cartilage differentiation. Moreover, blocking transient cartilage differentiation is sufficient for halting the progression of experimental osteoarthritis. A developmental biology inspired approach that combines restoration of tissue microenvironment, supplementation with engineered cartilage and built in mechanism to prevent transient cartilage differentiation could be an avenue for developing a disease modifying therapy for osteoarthritis.

Early intervention of swimming exercises attenuate articular cartilage destruction in a rat model of anterior cruciate ligament and meniscus knee injuries

AIM

The anterior cruciate ligament (ACL) and meniscus injuries often cause post-traumatic knee osteoarthritis (PTOA), which can place great limitations on patients. But to date there is no effective therapy to delay the progression of cartilage destruction in PTOA. This study aimed to compare the effects of early versus delayed swimming exercise on the chondroprotective effects in a rat PTOA model with ACL and meniscus injuries.

MAIN METHODS

Thirty-two adult male Sprague-Dawley rats received unilateral ACL transection and medial meniscectomy (ACLMT). These were randomly allocated to four groups: early swimming (eSW), delayed swimming (dSW), sham-operated early swimming (sham-eSW) and sham-operated delayed swimming (sham-dSW). Swimming (30 min per session) continuing for 28 days was started three days and three months after ACLMT surgery as a protocol for eSW and dSW intervention. Cartilage quality was assessed by Mankin HHGS examination (H&E, Safranin-O stain) and collagen type II (CoII) and matrix metalloproteases-13 (MMP13) immunohistochemistry.

KEY FINDINGS

ACLMT induced the PTOA histopathological changes, inhibited CoII and enhanced MMP13 expressions in cartilage for both sham-eSW and sham-dSW groups. eSW intervention significantly enhanced CoII expression and suppressed MMP13 overexpression in superficial and transitional zones of cartilage, as well as better Mankin scores, corresponding to sham-swimming controls (P < 0.05). dSW intervention provided less enhancement of CoII expression and improvement of histopathological scoring, but significantly reduced MMP13 overexpression compared to animals in eSW (P < 0.05).

SIGNIFICANCE

Early intervention by swimming at very early stages of cartilage damage provides greater benefits than delayed intervention when PTOA has already developed.

Extension of knee immobilization delays recovery of histological damages in the anterior cruciate ligament insertion and articular cartilage in rabbits

[Purpose] To investigate the influence of knee immobilization period on recovery of histological damages in the anterior cruciate ligament (ACL) insertion and articular cartilage in rabbits. This knowledge is important for determining the appropriate rehabilitation approach for patients with ligament injuries, fracture, disuse atrophy, and degenerative joint disease. [Materials and Methods] Forty-eight male Japanese white rabbits were divided equally into the remobilization and control groups. The remobilization group had the right knee surgically immobilized, and was divided equally into four subgroups according to the duration of immobilization (1, 2, 4 and 8 weeks). After the immobilization was removed, the rabbits moved freely for 8 weeks. The control group underwent sham operation and followed the same time course as the remobilization group. The chondrocyte apoptosis rate and chondrocyte proliferation rate in the ACL insertion and articular cartilage were analyzed after remobilization. [Results] In the ACL insertion, the remobilization group had a higher chondrocyte apoptosis rate than the control group after 8 weeks of immobilization, and a lower chondrocyte proliferation rate than the control group after 4 and 8 weeks of immobilization. In the articular cartilage, the remobilization group had a lower chondrocyte proliferation rate than the control group after 8 weeks of immobilization. After 8 weeks of remobilization, the ACL insertion and articular cartilage are not completely recovered after 4 and 8 weeks of immobilization, respectively. [Conclusion] Our results suggest that 8 weeks of remobilization will result in recovery of the ACL insertion after 2 weeks of knee immobilization, and recovery of the articular cartilage after 4 weeks of knee immobilization. If 8 weeks of immobilization occurs, a remobilization duration of more than 8 weeks may be necessary.

Bone replaces articular cartilage in the rat knee joint after prolonged immobilization

BACKGROUND

Lost joint range of motion (ROM) is common in chronic osteoarthritis, alters regional weight-bearing across the articular surfaces, and contributes to loss of cartilage and bone alterations. Limited data exist on the regional effects on joints subjected to chronic losses of ROM.

OBJECTIVE

To characterize the regional replacement by bone as part of articular cartilage degeneration after prolonged immobilization.

METHODS

Eleven rat knees were rigidly-immobilized in flexion for 32weeks with contralateral and sham-operated (n=6) knees as controls. Sagittal medial tibial epiphysis histological sections assessed the anterior (non-weight-bearing), middle and posterior (both weight-bearing) regions. We quantified the distribution of collagen I, collagen II, cartilage thickness, glycosaminoglycan (GAG) staining, Mankin scoring, and subchondral bone plate cross-sectional area. Using immunohistochemistry (IHC), we visualized blood vessels, osteoblasts, and mesenchymal stem cells (MSCs).

RESULTS

Immobilized cartilage had increased collagen I content in the anterior tibial region with picrosirius red staining (immobilized=61±20%; contralateral=43±12%, p=0.033; sham=20±10%, p=0.028) and collagen I IHC (immobilized=40±10%; contralateral=11±4%, p=0.003; sham=5±3%, p=0.043). Articular cartilage was thinner anteriorly (18±30μm) in immobilized knees versus contralateral (124±40μm, p<0.001) and sham (125±43μm, p=0.043). GAG staining covered 2±4% of the anterior articular area in immobilized knees versus 28±12% contralaterally (p=0.003) and 26±7% in sham (p=0.043). Mankin scores in immobilized knees were 4.7±1.7 versus 0.2±0.4 and 0±0 for contralateral and sham (p=0.003, p=0.042), respectively. The trabecular bone plate area of anterior and posterior regions showed relative loss of cross-sectional area in immobilized knees compared to controls (immobilized/contralateral area ratios of 0.67 and 0.46 respectively, both p=0.003), while the area in the middle region was preserved. Movat's pentachrome stain and CD31 staining showed chondral vascular ingrowth from subchondral bone. Osteocalcin and CD90 MSC staining were decreased in immobilized knees versus contralateral (p=0.003, p=0.036 respectively).

CONCLUSIONS

Bony replacement characterizes articular cartilage degeneration of knees immobilized for 32weeks in the anterior, non-weight bearing region of the tibia. Replacement of cartilage by bone may have been mediated by chondral vascularization, suggesting irreversible changes. These findings stress the importance of weight-bearing and joint motion to maintain cartilage structure.

Joint Contractures Resulting From Prolonged Immobilization: Etiology, Prevention, and Management

Patients who are immobilized for a prolonged period are at risk for developing joint contractures, which often affect functional outcomes. Nonsurgical interventions are useful for preventing joint contractures. However, once contractures develop, these interventions frequently fail to restore function over the long term. To increase the rehabilitation potential of an extremity with refractory function-limiting contractures, surgery is often required.

Unloading results in rapid loss of TGFβ signaling in articular cartilage: role of loading-induced TGFβ signaling in maintenance of articular chondrocyte phenotype?

OBJECTIVE

Recently it was shown that loading of articular cartilage explants activates TGFβ signaling. Here we investigated if in vivo chondrocytes express permanently high TGFβ signaling, and the consequence of the loss of compressive loading-mediated TGFβ signaling on chondrocyte function and phenotype.

METHOD

Bovine articular cartilage explants were collected within 10 min post mortem and stained immediately and after 30, 60 and 360 min for phosphorylated-Smad2, indicating active TGFβ signaling. Explants were unloaded for 48 h and subsequently repeatedly loaded with a compressive load of 3 MPa. In addition, explants were cultured unloaded for 2 weeks and the effect of loading or exogenous TGFβ on proteoglycan level and chondrocyte phenotype (Col10a1 mRNA expression) was analyzed.

RESULTS

Unloading of articular cartilage results in rapid loss of TGFβ signaling while subsequent compressive loading swiftly restored this. Loading and exogenous TGFβ enhanced expression of TGFβ1 and ALK5. Unloading of explants for 2 weeks resulted in proteoglycan loss and increased Col10a1 expression. Both loading and exogenous TGFβ inhibited elevated Col10a1 expression but not proteoglycan loss.

CONCLUSION

Our data might imply that in vivo regular physiological loading of articular cartilage leads to enduring TGFβ signaling and TGFβ-induced gene expression. We propose a hypothetical model in which loading activates a self-perpetuating system that prevents hypertrophic differentiation of chondrocytes and is crucial for cartilage homeostasis.

Remobilization causes site-specific cyst formation in immobilization-induced knee cartilage degeneration in an immobilized rat model

An understanding of the articular cartilage degenerative process is necessary for the prevention and treatment of joint disease. The present study aimed to examine how long‐term immobilization‐induced cartilage degeneration is aggravated by remobilization. Sixty 8‐week‐old male Wistar rats were used in this study. The unilateral knee joint was immobilized using an external fixator for 8 weeks. The rats were killed at 0 and 3 days, and at 1, 2, 4 and 8 weeks after removing the fixator. After the rats were killed, the maximum knee extension angles were measured. Histological sections at the medial mid‐condylar region (non‐contact, transitional and contact regions of the femur and tibia) were prepared and scored. The cartilage thickness and number of chondrocytes were measured, and CD44 and Col2‐3/4c expression levels were assessed immunohistochemically. The histological assessment revealed progressive aggravation of cartilage degeneration in the transitional region, with a decreased number of chondrocytes and CD44‐positive chondrocytes as well as poor scoring over time, particularly in the tibia. Cyst formation was confirmed in the transitional region of the tibia at 8 weeks post‐remobilization. The cartilage thickness in the transitional region was thicker than that in the contact region, particularly in the tibia. Col2‐3/4c expression was observed in the non‐contact and transitional regions, and the knee extension angle was recovered. In conclusion, immobilization‐induced cartilage degeneration was aggravated by remobilization over time in the transitional region, followed by observations of a decreased number of chondrocytes and morphological disparity between different cartilage regions.

Effects of physical exercise on the cartilage of ovariectomized rats submitted to immobilization

Objective

To analyze the effects of physical exercise on cartilage histomorphometry in osteoporosis-induced rats subjected to immobilization.

Methods

We used 36 Wistar rats that were separated into six groups: G1, G2 and G3 submitted to pseudo-oophorectomy, and G4, G5 and G6 submitted to oophorectomy. After 60 days at rest, G2, G3, G5 and G6 had the right hind limbs immobilized for 15 days, followed by the same period in remobilization, being free in the box to G2 and G5, and climb ladder to G3 and G6. At the end of the experiment, the rats were euthanized, their tibias bilaterally removed and submitted to histological routine.

Results

There was significant increase in thickness of the articular cartilage (F(5;29)=13.88; p<0.0001) and epiphyseal plate (F(5;29)=14.72; p<0.0001) as the number of chondrocytes (F(5;29)=5.11; p=0.0021) in ovariectomized rats, immobilized and submitted to exercise. In the morphological analysis, degeneration of articular cartilage with subchondral bone exposure, loss of cellular organization, discontinuity of tidemark, presence of cracks and flocculation in ovariectomized, immobilized and free remobilization rats were found. In ovariectomized and immobilized remobilization ladder rats, signs of repair of the cartilaginous structures in the presence of clones, pannus, subcortical blood vessel invasion in the calcified zone, increasing the amount of isogenous groups and thickness of the calcified zone were observed.

Conclusion

Exercise climb ladder was effective in cartilaginous tissue recovery process damaged by immobilization, in model of osteoporosis by ovariectomy in rats.

Cartilage matrix changes in contralateral mobile knees in a rabbit model of osteoarthritis induced by immobilization

Background

Many researches have investigated the changes associated with immobilization-induced osteoarthritis (OA). However, there are only few studies focusing on the effect of unilateral knee immobilization on cartilage matrix changes in the contralateral mobile knee. The aim of the present study was to investigate the influence of immobilization on the cartilage matrix in the contralateral mobile knees in a rabbit model of OA induced by immobilization.

Methods

Right knees (experimental knees) of eighteen mature female rabbits were immobilized at an extension of 180° with orthopedic casting tape for 2, 4, or 8 weeks. Left knees (contralateral knees) of the immobilized rabbits were not subjected to immobilization. The knees of six non-immobilized rabbits were designated as control knees. Following immobilization, cartilage specimens from the medial femoral condyle underwent macroscopic, histological, immunohistochemical, and biochemical evaluations.

Results

Roughness of cartilage surface was detected in the experimental knees at 2 weeks, and cartilage degeneration was further developed. In the contralateral knee, cartilage showed degenerative changes after 4 weeks. Safranin-O staining and glycosaminoglycan (GAG) contents were reduced in the experimental knees following immobilization and in the contralateral intact knees after 4 and 8 weeks. Type II collagen staining was gradually reduced, type I collagen accumulation was obviously detected in the upper and middle layers of cartilage in experimental knees after 8 weeks, and the collagen orientation was gradually disorganized in both knees at 4 and 8 weeks. For both experimental and contralateral knees, collagen contents were significantly decreased at 8 weeks, and Mankin and Osteoarthritis Research Society International (OARSI) scores increased over time.

Conclusion

OA developed in the contralateral intact knee with the progress of OA in the immobilized knee in a rabbit model of immobilization-induced OA.

Using 7.0T MRI T2 mapping to detect early changes of the cartilage matrix caused by immobilization in a rabbit model of immobilization-induced osteoarthritis

OBJECTIVE

The goal of this study was to detect early changes in the cartilage matrix caused by immobilization in a rabbit model of immobilization-induced osteoarthritis (OA) by T2 mapping with 7.0T MRI.

MATERIALS AND METHODS

Left knee joints of 28 mature rabbits were immobilized at 180° of extension with orthopedic casting tape for 1, 2, or 3weeks (n=7 rabbits each). No immobilization was performed in the control group (n=7 rabbits). T2 mapping was performed after 1, 2, and 3weeks. Osteochondral specimens harvested from the trochlea groove (TG) and medial femoral condyle (MFC) were subjected to histologic, immunohistochemical, and microscopic evaluation, followed by biochemical assays for water, glycosaminoglycan (GAG), and collagen. The ability of T2 mapping to reveal changes in the cartilage matrix was further assessed.

RESULTS

Rabbits demonstrated elevated T2 values (9.9% in TG, 10.6% in MFC), a dulled cartilage surface, reduced Safranin-O staining, and decreased GAG content (14.2% in TG and MFC) after 2weeks, with cartilage surface softening, irregularity, and markedly reduced GAG content by 3weeks. T2 values were correlated positively with water (r=0.836 in TG, r=0.821 in MFC) and negatively with GAG content (r=-0.945 in TG, r=-0.957 in MFC), but had no discernible relationship with collagen content (r=-0.196 in TG, r=-0.213 in MFC).

CONCLUSIONS

7.0T MRI T2 mapping can be used to detect early changes of the cartilage matrix caused by immobilization in an immobilization-induced OA model.

Análise termogravimétrica da cartilagem articular de ratos exercitados após imobilização

INTRODUÇÃO: A imobilização articular é uma técnica de tratamento frequentemente utilizada na ortopedia e, associada ao processo de senescência, promove alterações tanto na estrutura quanto na síntese e biomecânica do tecido cartilaginoso. OBJETIVO: Descrever os efeitos da imobilização, da remobilização livre e por meio de exercício físico sobre a cartilagem articular de ratos situados em duas faixas etárias. MÉTODOS: Trinta e nove ratos Wistar divididos em dois grupos etários, um grupo adulto (cinco meses de idade) e um idoso (15 meses de idade), subdivididos em: controle, imobilizado, remobilizado livre e remobilizado por meio de exercício físico. Os membros posteriores dos ratos foram imobilizados por sete dias. O protocolo de exercícios foi composto por cinco sessões diárias de natação, de 25 minutos cada. A cartilagem articular do quadril foi submetida à análise termogravimétrica, tendo sido avaliado seu conteúdo de água. RESULTADOS: Nos animais adultos a imobilização reduziu a quantidade de água presente no tecido cartilaginoso, e os protocolos de remobilização foram eficazes para restabelecer a condição inicial do tecido. Nos animais idosos não houve diferença significativa entre os grupos, porém o grupo idoso controle obteve resultado significantemente menor que o grupo adulto controle (X: 13,10 ± 5,24 vs 10,70 ± 1,95). CONCLUSÕES: A imobilização e o processo de senescência induzem a diminuição do conteúdo de água da cartilagem articular e os protocolos de remobilização foram eficientes para restabelecer esta propriedade apenas nos animais adultos.

Alteration of cartilage surface collagen fibers differs locally after immobilization of knee joints in rats

The purpose of this study was to examine the ultrastructural changes of surface cartilage collagen fibers, which differ by region and the length of the experimental period in an immobilization model of rat. Male Wistar rats were randomly divided into histological or macroscopic and ultrastructural assessment groups. The left knees of all the animals were surgically immobilized by external fixation for 1, 2, 4, 8 or 16 weeks (n = 5/time point). Sagittal histological sections of the medial mid-condylar region of the knee were obtained and assessed in four specific regions (contact and peripheral regions of the femur and tibia) and two zones (superficial and deep). To semi-quantify the staining intensity of the collagen fibers in the cartilage, picrosirius red staining was used. The cartilage surface changes of all the assessed regions were investigated by scanning electron microscopy (SEM). From histological and SEM observations, the fibrillation and irregular changes of the cartilage surface were more severe in the peripheral region than in the contact region. Interestingly, at 16 weeks post-immobilization, we observed non-fibrous structures at both the contact and peripheral regions. The collagen fiber staining intensity decreased in the contact region compared with the peripheral region. In conclusion, the alteration of surface collagen fiber ultrastructure and collagen staining intensity differed by the specific cartilage regions after immobilization. These results demonstrate that the progressive degeneration of cartilage is region specific, and depends on the length of the immobilization period.

Effects of immobilization and remobilization on the ankle joint in Wistar rats

A sprained ankle is a common musculoskeletal sports injury and it is often treated by immobilization of the joint. Despite the beneficial effects of this therapeutic measure, the high prevalence of residual symptoms affects the quality of life, and remobilization of the joint can reverse this situation. The aim of this study was to analyze the effects of immobilization and remobilization on the ankle joint of Wistar rats. Eighteen male rats had their right hindlimb immobilized for 15 days, and were divided into the following groups: G1, immobilized; G2, remobilized freely for 14 days; and G3, remobilized by swimming and jumping in water for 14 days, performed on alternate days, with progression of time and a series of exercises. The contralateral limb was the control. After the experimental period, the ankle joints were processed for microscopic analysis. Histomorphometry did not show any significant differences between the control and immobilized/remobilized groups and members, in terms of number of chondrocytes and thickness of the articular cartilage of the tibia and talus. Morphological analysis of animals from G1 showed significant degenerative lesions in the talus, such as exposure of the subchondral bone, flocculation, and cracks between the anterior and mid-regions of the articular cartilage and the synovial membrane. Remobilization by therapeutic exercise in water led to recovery in the articular cartilage and synovial membrane of the ankle joint when compared with free remobilization, and it was shown to be an effective therapeutic measure in the recovery of the ankle joint.

Orthotic considerations for dense connective tissue and articular cartilage--the need for optimal movement and stress

Orthotic intervention is an essential component of hand rehabilitation, addressing biological factors that affect activity and participation. Functional, pain-free joint mobility requires skeletal stability, healthy articular cartilage, and appropriate extensibility of periarticular dense connective tissues (DCTs). This article addresses basic science underlying clinical reasoning when considering orthoses to maintain or restore structural integrity, mobility and function of DCT structures, and articular cartilage. However, these tissues often have different and sometimes conflicting requirements for the maintenance and restoration of integrity and health. The duration of immobilization, especially at end range, should be carefully considered, as it impairs nutrition of tissues and adversely compresses articular cartilage, causing injury that may not be reversible. Immobilization also reduces extensibility of DCT. Thus, an intermittent orthotic wearing schedule is suggested, allowing movement wherever possible to promote tissue health. To optimize benefits and minimize harmful effects of orthotic intervention, further research on physiological responses of human tissues to immobilization and tension is needed.

Remobilization does not restore immobilization-induced adhesion of capsule and restricted joint motion in rat knee joints

Joint immobilization, which is used in orthopaedic treatments and observed in bedridden people, usually causes restricted joint motion. Decreased joint motion diminishes activities of daily living and increases burden of nursing-care. The purpose of this study was to clarify the reversibility of immobilization-induced capsular changes and restricted joint motion in rat knee joints. The unilateral knee joints of adult male rats were immobilized with an internal fixator for 1, 2, 4, 8, and 16 weeks as a model of immobilization after surgery or disuse of the joint. After the fixation devices were removed, the rats were allowed to move freely for 16 weeks. Sham-operated rats were used as controls. Sagittal sections at medial midcondylar regions were made and assessed with histological, histomorphometric, and immunohistochemical methods. Joint motion was measured using a custom-made device under x-ray control after removal of the periarticular muscles. In the 1/16-week and 2/16-week immobilization-remobilization (Im-Rm) groups, cord-like structures connecting the superior and inferior portions of the posterior capsule (partial adhesion) were observed without restricted joint motion. In the 4/16-, 8/16-, and 16/16-week Im-Rm groups, global adhesion of the posterior capsule and restricted joint motion were observed. The restricted joint motion was not completely restored after incision of the posterior capsule. These data indicate that immobilization alone causes irreversible capsular changes and arthrogenic restricted joint motion. Besides the joint capsule, other arthrogenic factors such as ligaments might influence the restricted joint motion. Prolonged immobilization over 4 weeks should be avoided to prevent irreversible joint contracture.

Progression of articular cartilage degeneration after application of muscle stretch

The aim of study was to evaluate the progression of the ankle articular cartilage alterations after a post-immobilization muscle stretching. Twenty-nine Wistar rats were separated into five groups: C--control, S--stretched, SR--stretch recovery, IS--immobilized and stretched, and ISR--immobilized stretched recovery. The immobilization was maintained for 4 weeks and the left ankle was then stretched manually through a full dorsal flexion for 10 times for 60 s with a 30 s interval between each 60 s period, 7 days/week for 3 weeks. The recovery period was of 7 weeks. At the end of the experiment, the left ankles were removed, processed in paraffin, and stained in hematoxylin-eosin and safranin O. Two blinded observers evaluated the articular cartilage using the Mankin grading system (cellularity, chondrocyte cloning, and proteoglycan content) through light microscopy, and performed the morphometry (cellularity, total thickness, non-calcified thickness, and calcified thickness measures). Both the Mankin grading system and the morphometric analysis showed that the ISR group presented the most increased cellularity among the groups. The IS and SR groups showed the highest proteoglycan loss, and the ISR group showed the same content of proteoglycan observed in the C group. No significant differences were found in the chondrocyte cloning, the total cartilage thickness, the non-calcified cartilage thickness, and the calcified cartilage thickness among the groups. The results suggest that the cartilage can recover the proteoglycan loss caused by immobilization and stretching, probably because of the increased chondrocyte density. Therefore, the ankle articular cartilage responded as to repair the metabolic deficits.