The effect of a passive muscle stretching protocol on the articular cartilage

Post-traumatic osteoarthritis of the ankle: A distinct clinical entity requiring new research approaches

The diagnosis of ankle osteoarthritis (OA) is increasing as a result of advancements in non-invasive imaging modalities such as magnetic resonance imaging, improved arthroscopic surgical technology and heightened awareness among clinicians. Unlike OA of the knee, primary or age-related ankle OA is rare, with the majority of ankle OA classified as post-traumatic (PTOA). Ankle trauma, more specifically ankle sprain, is the single most common athletic injury, and no effective therapies are available to prevent or slow progression of PTOA. Despite the high incidence of ankle trauma and OA, ankle-related OA research is sparse, with the majority of clinical and basic studies pertaining to the knee joint. Fundamental differences exist between joints including their structure and molecular composition, response to trauma, susceptibility to OA, clinical manifestations of disease, and response to treatment. Considerable evidence suggests that research findings from knee should not be extrapolated to the ankle, however few ankle-specific preclinical models of PTOA are currently available. The objective of this article is to review the current state of ankle OA investigation, highlighting important differences between the ankle and knee that may limit the extent to which research findings from knee models are applicable to the ankle joint. Considerations for the development of new ankle-specific, clinically relevant animal models are discussed. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:440-453, 2017.

Stretching After Heat But Not After Cold Decreases Contractures After Spinal Cord Injury in Rats

BACKGROUND

Contractures are a prevalent and potentially severe complication in patients with neurologic disorders. Although heat, cold, and stretching are commonly used for treatment of contractures and/or spasticity (the cause of many contractures), the sequential effects of these modalities remain unclear.

QUESTIONS/PURPOSES

Using an established rat model with spinal cord injury with knee flexion contracture, we sought to determine what combination of heat or cold before stretching is the most effective for treatment of contractures derived from spastic paralyses and investigated which treatment leads to the best (1) improvement in the loss of ROM; (2) restoration of deterioration in the muscular and articular factors responsible for contractures; and (3) amelioration of histopathologic features such as muscular fibrosis in biceps femoris and shortening of the joint capsule.

METHODS

Forty-two adolescent male Wistar rats were used. After spasticity developed at 2 weeks postinjury, each animal with spinal cord injury underwent the treatment protocol daily for 1 week. Knee extension ROM was measured with a goniometer by two examiners blinded to each other's scores. The muscular and articular factors contributing to contractures were calculated by measuring ROM before and after the myotomies. We quantitatively measured the muscular fibrosis and the synovial intima length, and observed the distribution of collagen of skeletal muscle. The results were confirmed by a blinded observer.

RESULTS

The ROM of heat alone (34° ± 1°) and cold alone (34° ± 2°) rats were not different with the numbers available from that of rats with spinal cord injury (35° ± 2°) (p = 0.92 and 0.89, respectively). Stretching after heat (24° ± 1°) was more effective than stretching alone (27° ± 3°) at increasing ROM (p < 0.001). Contrastingly, there was no difference between stretching after cold (25° ± 1°) and stretching alone (p = 0.352). Stretching after heat was the most effective for percentage improvement of muscular (29%) and articular (50%) factors of contractures. Although quantification of muscular fibrosis in the rats with spinal cord injury (11% ± 1%) was higher than that of controls (9% ± 0.4%) (p = 0.01), no difference was found between spinal cord injury and each treatment protocol. The total synovial intima length of rats with spinal cord injury (5.9 ± 0.2 mm) became shorter than those of the controls (7.6 ± 0.2 mm) (p < 0.001), and those of stretching alone (6.9 ± 0.4 mm), stretching after heat (7.1 ± 0.3 mm), and stretching after cold (6.7 ± 0.4 mm) increased compared with rats with spinal cord injury (p = 0.01, p = 0.001, and p = 0.04, respectively). The staining intensity and pattern of collagen showed no difference among the treatment protocols.

CONCLUSIONS

This animal study implies that heat or cold alone is ineffective, and that stretching is helpful for the correction of contractures after spinal cord injury. In addition, we provide evidence that heat is more beneficial than cold to increase the effectiveness of stretching.

CLINICAL RELEVANCE

Our findings tend to support the idea that stretching after heat can improve the loss of ROM and histopathologic features of joint tissues. However, further studies are warranted to determine if our findings are clinically applicable.

Effectiveness of an aquatic exercise program and low-level laser therapy on articular cartilage in an experimental model of osteoarthritis in rats

OBJECTIVE

The aim of this study was to evaluate the effects of an aquatic exercise program and low-level laser therapy (LLLT) (associated or not) on degenerative modifications and inflammatory mediators on the articular cartilage using an experimental model of knee OA.

METHOD

Forty male Wistar rats were divided into 4 groups: knee OA - without treatment (OA); OA plus exercise program group (OAE); OA plus LLLT (OAL); OA plus exercise program associated with LLLT (OAEL). Trained rats performed a water-jumping program carrying a load equivalent to 50-80 % of their body mass strapped to their chest. The laser irradiation was used either as the only method or after the exercise training had been performed, at 2 points contact mode (medial and lateral side of the left joint). The treatments started 4 weeks after the surgery, 3 days/week for 8 weeks.

RESULTS

The results revealed that all treated groups (irradiated or not) exhibited a better pattern of tissue organization, with less fibrillation and irregularities along the articular surface and improved chondrocytes organization. Also, a lower cellular density and structural damage (OARSI score) and higher thickness values were observed in all treated groups. Additionally, OAE and OAEL showed a reduced expression in IL-1β and caspase-3 as compared with OA. Furthermore, a statistically lower MMP-13 expression was only observed in OAEL as compared with OA.

CONCLUSION

These results suggest that aquatic exercise program and LLLT were effective in preventing cartilage degeneration. Also, physical exercise program presented anti-inflammatory effects in the knees in OA rats.

Aerobic exercise training and low-level laser therapy modulate inflammatory response and degenerative process in an experimental model of knee osteoarthritis in rats

OBJECTIVE

The aim of this study was to evaluate the effects of an aerobic exercise training and low-level laser therapy (LLLT) (associated or not) on degenerative modifications and inflammatory mediators on the articular cartilage using an experimental model of knee OA.

MATERIAL AND METHODS

Fifty male Wistar rats were randomly divided into five groups: control group (CG); knee OA control group (OAC); OA plus exercise training group (OAT); OA plus LLLT group (OAL); OA plus exercise training associated with LLLT group (OATL). The exercise training (treadmill; 16 m/min; 50 min/day) and the laser irradiation (two points-medial and lateral side of the left joint; 24 sessions) started 4 weeks after the surgery, 3 days/week for 8 weeks.

RESULTS

The results showed that all treated groups showed (irradiated or not) a better pattern of tissue organization, with less fibrillation and irregularities along the articular surface and chondrocytes organization, a lower degenerative process measured by OARSI score and higher thickness values. Additionally, all treated group showed a reduced expression in IL-1β, caspase-3 and MMP-13 compared to OAC. Moreover, a lower caspase-3 expression was observed in OATL compared to OAL and OAT.

CONCLUSION

These results suggest that exercise training and LLLT were effective in preventing cartilage degeneration and modulating inflammatory process induced by knee OA.

Use of micro-computed tomography to evaluate the effects of exercise on preventing the degeneration of articular cartilage in tail-suspended rats

Space flight has been shown to induce bone loss and muscle atrophy, which could initiate the degeneration of articular cartilage. Countermeasures to prevent bone loss and muscle atrophy have been explored, but few spaceflight or ground-based studies have focused on the effects on cartilage degeneration. In this study, we investigated the effects of exercise on articular cartilage deterioration in tail-suspended rats. Thirty-two female Sprague-Dawley rats were randomly divided into four groups (n=8 in each): tail suspension (TS), tail suspension plus passive motion (TSP), tail suspension plus active exercise (TSA), and control (CON) groups. In the TS, TSP, and TSA groups, the rat hindlimbs were unloaded for 21 days by tail suspension. Next, the cartilage thickness and volume, and the attenuation coefficient of the distal femur were evaluated by micro-computed tomography (μCT). Histological analysis was used to assess the surface integrity of the cartilage, cartilage thickness, and chondrocytes. The results showed that: (1) the cartilage thickness on the distal femur was significantly lower in the TS and TSP groups compared with the CON and TSA groups; (2) the cartilage volume in the TS group was significantly lower compared with the CON, TSA, and TSP groups; and (3) histomorphology showed that the chondrocytes formed clusters where the degree of matrix staining was lower in the TS and TSP groups. There were no significant differences between any of these parameters in the CON and TSA groups. The cartilage thickness measurements obtained by μCT and histomorphology correlated well. In general, tail suspension could induce articular cartilage degeneration, but active exercise was effective in preventing this degeneration in tail-suspended rats.

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.

Low-level laser therapy prevents degenerative morphological changes in an experimental model of anterior cruciate ligament transection in rats

The aim of this study was to analyze the effects of low-level laser therapy (LLLT) on the prevention of cartilage damage after the anterior cruciate ligament transection (ACLT) in knees of rats. Thirty male rats (Wistar) were distributed into three groups (n = 10 each): injured control group (CG); injured laser-treated group at 10 J/cm(2) (L10), and injured laser-treated group at 50 J/cm(2) (L50). Laser treatment started immediately after the surgery and it was performed for 15 sessions. An 808 nm laser, at 10 and 50 J/cm(2), was used. To evaluate the effects of LLLT, the qualitative and semi-quantitative histological, morphometric, and immunohistochemistry analysis were performed. Initial signs of tissue degradation were observed in CG. Interestingly, laser-treated animals presented a better tissue organization, especially at the fluence of 10 J/cm(2). Furthermore, laser phototherapy was able of modulating some of the aspects related to the degenerative process, such as the prevention of proteoglycans loss and the increase in cartilage area. However, LLLT was not able of modulating chondrocytes proliferation and the immunoexpression of markers related to inflammatory process (IL-1 and MMP-13). This study showed that 808 nm laser, at both fluences, prevented features related to the articular degenerative process in the knees of rats after ACLT.

Amount of torque and duration of stretching affects correction of knee contracture in a rat model of spinal cord injury

BACKGROUND

Joint contractures are a common complication of many neurologic conditions, and stretching often is advocated to prevent and treat these contractures. However, the magnitude and duration of the stretching done in practice usually are guided by subjective clinical impressions.

QUESTIONS/PURPOSES

Using an established T8 spinal cord injury rat model of knee contracture, we sought to determine what combination of static or intermittent stretching, varied by magnitude (high or low) and duration (long or short), leads to the best (1) improvement in the limitation in ROM; (2) restoration of the muscular and articular factors leading to contractures; and (3) prevention and treatment of contracture-associated histologic alterations of joint capsule and articular cartilage.

METHODS

Using a rat animal model, the spinal cord was transected completely at the level of T8. The rats were randomly assigned to seven treatment groups (n = 4 per group), which were composed of static or intermittent stretching in combination with different amounts of applied torque magnitude and duration. We assessed the effect of stretching by measuring the ROM and evaluating the histologic alteration of the capsule and cartilage.

RESULTS

Contractures improved in all treated groups except for the low-torque and short-duration static stretching conditions. High-torque stretching was effective against shortening of the synovial membrane and adhesions in the posterosuperior regions. Collagen Type II and VEGF in the cartilage were increased by stretching.

CONCLUSIONS

High-torque and long-duration static stretching led to greater restoration of ROM than the other torque and duration treatment groups. Stretching was more effective in improving articular components of contractures compared with the muscular components. Stretching in this rat model prevented shortening and adhesion of the joint capsule, and affected biochemical composition, but did not change morphologic features of the cartilage.

CLINICAL RELEVANCE

This animal study tends to support the ideas that static stretching can influence joint ROM and histologic qualities of joint tissues, and that the way stretching is performed influences its efficacy. However, further studies are warranted to determine if our findings are clinically applicable.

Muscle stretching after immobilization applied at alternate days preserves components of articular cartilage

We compared the response of articular cartilage subjected to muscle stretching at different frequencies after joint immobilization. Wistar rats with immobilized left hind limbs were classified into the following groups: immobilization, immobilization followed by muscle stretching applied daily (group IS7) or three times a week (IS3), muscle stretching applied daily (S7) or three times a week (S3), and a control group (C) that underwent no intervention. We then evaluated the cartilage for cellularity, loss of proteoglycans, collagen density, and immunostaining of fibronectin and chondroitin 4-sulfate. Group IS7 showed a significant increase in cellularity and significant loss of proteoglycan compared with the control. In addition, IS7 group had less proteoglycan than IS3. Thin collagen fibrils were significantly reduced in IS7 rats, compared with IS3 and C. There was a significant decrease in the amount of thick fibrils in all groups compared with the control. Groups IS7 and IS3 showed significantly more intense fibronectin immunostaining than the other groups. Our results show that if applied daily after immobilization, muscle stretching is harmful to articular cartilage. However, when applied on alternate days, muscle stretching preserves the components of articular cartilage. We suggest that the latter frequency is more suitable for treatment.

Intensity-dependent effect of treadmill running on knee articular cartilage in a rat model

OBJECTIVE

To understand the changes of femoral cartilage in response to treadmill running with different intensities in the hope of differentiating "moderate" and "strenuous" running in a rat model.

METHOD

A total of 24 male Wistar rats were randomly assigned into groups of sedentary (SED), low-intensity running (LIR), medium-intensity running (MIR), and high-intensity running (HIR). Rats in LIR, MIR, and HIR groups underwent 8 weeks' treadmill running programs. After sacrificed, femoral condyles were collected to take histomorphometric analysis and immunohistochemistry for collagen II.

RESULTS

Gross and histological observation showed osteoarthritic changes in group HIR. In comparison to SED group, there was significant increase in cartilage thickness, number of chondrocytes, and GAG content in groups LIR and MIR. Conversely, decrease in cartilage thickness, chondrocyte number, and GAG content was found in rats of HIR group, without significant difference though. In addition, in comparison to SED group, HIR group exhibited disorganization of collagen fibril and significantly lower content of collagen type II.

CONCLUSION

An intensity-dependent effect was suggested on the articular cartilage. Our results also demonstrated that running with low-to-medium intensity applied in the present study should be regarded as "moderate" running, whereas high-intensity running as "strenuous" running.

Analysis of the deep digital flexor tendon in rats submitted to stretching after immobilization

Few studies have analyzed the effect of stretching after immobilization on the structural and biochemical properties of tendons. Here, the effect of stretching and immobilization on the proximal (p), intermediate (i), and distal (d) regions of the deep digital flexor tendon in rats was analyzed. The d region was subjected to compression and tension forces, the i region was subjected to compressive forces and the p region received tension forces. Rats were separated into five groups: GI--control for GII; GII--immobilized rats; GIII--control for GIV and GV groups; GIV--immobilized and stretched rats; and GV--immobilized rats which were allowed free cage activity. GII showed a higher molecular organization in the d and p regions as detected by measuring optical retardation, a lower concentration of hydroxyproline in the i region and a significant decrease in noncollagenous proteins found in the three regions of the tendon. Regarding the glycosaminoglycans, diminishing dermatan sulfate and the absence of chondroitin sulfate in the i region were observed in GII when compared to GI. However, in the same region of GIV, higher concentrations of chondroitin and dermatan sulfate were observed along with a strong metachromasy. An increase in hydroxyproline content in the i region and a higher molecular organization in the d and p regions were observed in GIV. Apparently, the active isoforms of metalloproteinase-2 also increased after stretching in all regions. These results suggest that stretching after immobilization contributed to the increase in molecular organization and to the synthesis of extracellular matrix components.

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.

The remodeling of collagen fibers in rats ankles submitted to immobilization and muscle stretch protocol

To evaluate the remodeling of collagen fibers in the articular cartilage of rat ankles, with and without immobilization, after application of muscle stretching protocol. Twenty three Wistar rats were divided into four groups: immobilized (I), n=6; immobilized and stretched (IS), n=6; stretched (S), n=6 and control (C), n=5. The animals in groups I and IS were submitted to immobilization. After the period of immobilization, the animals in groups IS and S were submitted to a muscle stretching protocol. At the end of the experiment, the animals were euthanized and the joints removed, processed and stained with Picrosirius red. The analysis was carried out using a polarized light microscope. The density of collagen fibers were quantified according to the intensity of birefringence displayed. By way of statistical analyses, the right and left hind limbs of the different groups were compared based on the total density of collagen fibers, the density of thick collagen fibers and the density of thin collagen fibers. Immobilization promoted a reduction in density of the thin fibers and of total collagen. The muscle stretching protocol after immobilization promoted a reduction in density of the total collagen and of the thick fibers, but the density of the thin fibers showed the same values as control. The collagen fibers were remodeled by the different stimuli. Immobilization was harmful to the collagen fibers and the muscle stretching protocol only recovered the thin collagen fibers.

Efeitos sobre o tecido ósseo e cartilagem articular provocados pela imobilização e remobilização em ratos Wistar

Longos períodos de imobilização conduzem à perda óssea e de propriedades do osso, e sua recuperação depende de vários fatores; além disso, a imobilização pode causar ulcerações no tecido cartilaginoso articular devido a alterações como perda de proteoglicanas, de massa e volume totais da cartilagem. O objetivo deste estudo foi verificar alterações histológicas, do tecido ósseo periarticular e da cartilagem articular, provocadas pela imobilização e remobilização de membros posteriores de ratos Wistar. Foram utilizados 12 ratos Wistar, divididos em dois grupos: GI - (n = 6): 15 dias com o membro posterior esquerdo imobilizado em plantiflexão, sendo o membro direito o controle; GR - (n = 6): período de 15 dias de remobilização livre na gaiola, associado a três séries diárias de alongamento do músculo sóleo esquerdo por 30 segundos. Foram avaliados no tecido ósseo as medidas de espessura do osso cortical, diâmetro do canal medular e número de osteócitos; no tecido cartilaginoso, foram mensurados a espessura média da cartilagem e o número de condrócitos. Como resultado, observou-se que para GI não houve alterações significativas na espessura do osso (p = 0,1156) nem no diâmetro do canal medular (p = 0,5698), mas diminuição significativa dos osteócitos em relação ao contralateral (p = 0,0005); em GR também houve decréscimo no número de osteócitos (p = 0,0001), mas as diferenças na espessura (p = 0,1343) e diâmetro do canal medular (p = 0,6456) mantiveram-se não significantes. Para os dados de cartilagem articular não houve diferenças significativas para as amostras, tanto na espessura da cartilagem para GI (p = 0,6640) e GR (p = 0,1633), quanto no número de condrócitos em GI (p = 0,9429) e GR (p = 0,1634). Conclui-se que duas semanas de imobilização e remobilização produziram apenas diminuição significativa no número de osteócitos nos ratos imobilizados; esse número continuou a diminuir mesmo nos animais remobilizados.

Changes in surface topologies of chondrocytes subjected to mechanical forces: an AFM analysis

The cartilage is composed of chondrocytes embedded in a matrix of collagen fibrils interspersed within a network of proteoglycans and is constantly exposed to biomechanical forces during normal joint movement. Characterization of the surface morphology, cytoskeletal structure, adherance and elastic properties of these mechanosensitive cells are crucial in understanding the effects of mechanical forces around a cell and how a cell responds to changes in its physical environment. In this work, we employed the atomic force microscope (AFM) to image cultured chondrocytes before and after subjecting them to mechanical forces in the presence or absence of interleukin-1beta to mimic inflammatory conditions. Nanoscale imaging and quantitative measurements from AFM data revealed that there are distinct changes in cell-surface topology and cytoskeleton arrangement in the cells following treatment with mechanical forces, IL-1beta or both. Our findings for the first time demonstrate that cultured chondrocytes are amenable to high-resolution AFM imaging and dynamic tensile forces may help overcome the effect of inflammatory factors on chondrocyte response.

Structural and biochemical analysis of the effect of immobilization followed by stretching on the calcaneal tendon of rats

Little is known about the stretching effects on the biochemical and morphological features of tendons submitted to a long period of immobilization. Our purpose was to evaluate the response of rat tendons to stretching procedures after immobilization. The animals were separated into five experimental groups: GI--control of immobilized and euthanized animals; GII--immobilized and euthanized animals; GIII--control of immobilized animals and afterward stretched or allowed free cage activity; GIV--immobilized and stretched animals; and GV--immobilized and allowed free cage activity. Analysis in SDS-PAGE showed no remarkable differences among the groups, but a prominent collagen band was observed in GV, as compared to GIV and the control group, both in the compression and tension regions. Hydroxyproline content was highest in the compression region of GII. No differences among the groups were observed in the tension region. In regard to the concentration of noncollagenous proteins, differences were detected only in the tension region, where larger concentrations were found in the GII. When GII and GIV were compared, highest values were found in the GII. A more abundant presence of sulfated glycosaminoglycans, especially chondroitin sulfate, was detected in GIV, at the compression region of tendons. The presence of dermatan sulfate was outstanding in the compression and tension regions of the GII and GV groups. In the Ponceau SS stained sections, analyzed under polarization microscopy, GII exhibited the highest disorganization of the collagen bundles, partially recovered after stretching or with only remobilization. Our results indicate that a revision in the stretching procedures, in terms of duration and periodicity of the sessions, could benefit the efficiency of the stretching in cases of previous immobilization of tendons.

Biomechanical signals suppress proinflammatory responses in cartilage: early events in experimental antigen-induced arthritis

Although biomechanical signals generated during joint mobilization are vital in maintaining integrity of inflamed cartilage, the molecular mechanisms of their actions are little understood. In an experimental model of arthritis, we demonstrate that biomechanical signals are potent anti-inflammatory signals that repress transcriptional activation of proinflammatory genes and augment expression of anti-inflammatory cytokine IL-10 to profoundly attenuate localized joint inflammation.