The authors would like to thank Joao Tomas for his technical assistance with the device and Khaoula Louati for assistance in developing the image analysis methods.

The rat knee immobilization model used has been approved by the University of Ottawa Animal Care and Veterinary Service and the local ethics committee.
1. Animal Preparation
<ol>
	<li>At the end of the predetermined immobilization period, euthanize the rats by administration of carbon dioxide. 
	NOTE: Here we used an immobilization model with a plate and 2 screws (one inserted in the proximal femur and the other in the distal tibia), which avoids violation of any knee joint structures, and maintains a knee-flexed position of 135&#176; as described previously6. Over a period of time, this produces a knee flexion contracture11.</li>
	<li>Cover the area both on and around the surface that the arthrometer will be placed upon with absorbent, water-proof protection pads. Wear gloves, lab coat, and eye protection, while completing the experiment.</li>
	<li>Using a scalpel, divide the skin to expose the plate and screws (see the note following step 1.1); insert the more proximal screw in the proximal femur and insert the more distal screw in the distal tibia. Palpate to locate the screws. Once the screw heads are accessible, remove the screw using a screwdriver. 
	NOTE: During the period of immobilization, the heads of the screws may become covered by soft tissue. If this occurs, use the scalpel to gently remove the tissue and uncover the screw heads.</li>
	<li>Once the screws are removed, remove the plate manually or using forceps from a dissection kit.</li>
	<li>Using scissors and forceps, deglove the lower extremity to remove skin from underlying fascia.</li>
</ol>
2. Animal Positioning on the Motor-driven Arthrometer
NOTE: All testing should be performed at room temperature. Here the arthrometer is powered by a standard North American 120 V input. The adapter output is 12 V and 500 mA.
<ol>
	<li>Position the animal to be tested on its side with the experimental leg (the leg to be tested) facing upwards (Figure 2).
	<ol>
		<li>Secure the femur in the grooved metal clamp that is integrated into the mounting stage of the arthrometer. Punch holes through the muscle using a precision screwdriver to place the clamp distal to the greater trochanter and secure the femur. Adjust the lateral femoral condyle over the center of rotation of the arthrometer (Figure&#160;1, 2).</li>
		<li>Position the movable arm with two upright posts behind the leg, just superior to the calcaneus, to push the knee into passive extension once the electric motor is activated.</li>
		<li>Tighten the femur clamp at its base using a hex key until it is secured.</li>
	</ol>
	</li>
	<li>Ensure the camera is correctly mounted on the arthrometer using a screwdriver and is on Manual Focus. Focus the camera on the femoral condyle.</li>
	<li>Select the direction setting on the arthrometer (clockwise or counterclockwise) depending on the direction of the knee ROM being tested and the position of the rat.</li>
	<li>Activate the arthrometer motor by simultaneously pushing the Power and Start button. 
	NOTE: The necessity of pushing the power and start button simultaneously is a safety feature of the device, which prevents accidental activation.
	<ol>
		<li>Observe that the arthrometer motor will move at a speed of 6.6 RPM and then stop for 2.1 s upon reaching the first pre-set torque.</li>
		<li>NOTE: that when the first torque is reached, the corresponding LED will light up and the digital camera will take a picture of the knee automatically. 
		NOTE: Once the picture is taken, the arthrometer will continue to the next, higher preset torque. Once the four torques have been applied, the arthrometer will stop. Once the rat is positioned on the arthrometer and testing is initiated, the total time for testing one knee is approximately 18.8 s. Times may vary slightly depending on the condition of the joint contracture. The images taken are used to measure the extension at each torque.</li>
	</ol>
	</li>
</ol>
3. Capturing the Angle of Knee Extension Using the Motor-driven Arthrometer
NOTE: Once the motor has stopped at each applied torque, a digital camera is triggered to take a picture. The camera is positioned on the frame such that it is directly above the knee joint being tested and focused on the femoral condyle.
<ol>
	<li>Continue testing with the same knee from the same animal but in a different situation, e.g., after a myotomy of the posterior transarticular muscles is performed to isolate the arthrogenic (non-muscular) component of a contracture, or with a knee from another animal.
	<ol>
		<li>When completing the myotomy, dissect the muscle proximal enough to the knee joint to ensure that the capsule is not cut. 
		NOTE: It is easiest to complete the myotomy when the leg is in extension, following application of torque setting 4 (17.53 N-cm). Then, repeat steps 2.1 through 3.1.</li>
	</ol>
	</li>
	<li>Once both legs have been tested in all conditions (e.g., before and after myotomy), dispose of the animal carcass and all biohazardous materials following institutional protocol, and clean the arthrometer.</li>
</ol>
4. Knee ROM Measurement Analysis
<ol>
	<li>Analyze ROM using ImageJ. 
	NOTE: Here version 1.45s was used.</li>
	<li>Open the file containing the digital image taken by the camera mounted on the rat arthrometer. 
	NOTE: The person performing the analysis should be blinded to the experimental grouping of the animal (e.g., immobilized versus control).</li>
	<li>Select the Angle tool from the main toolbar and trace the femorotibial angle by drawing a femoral line from the middle of the femur clamp to the lateral condyle (aligned with the femoral diaphysis, Figure 2), and a tibial line from the lateral femoral condyle to the lateral malleolus (Figure 2). 
	NOTE: The femoro-tibial angle corresponds to the maximal angle of knee extension reached at each preset torque.</li>
	<li>Use the measuring tool by clicking Analyze| Measure to show the calculated angle produced by the 2 lines drawn above. Use the convention of 0&#176; to mean full extension.</li>
</ol>

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M., Reilly, K., Laneuville, O., Uhthoff, H., Trudel, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+replaces+articular+cartilage+in+the+rat+knee+joint+after+prolonged+immobilization.">Bone replaces articular cartilage in the rat knee joint after prolonged immobilization.</a> Bone. 106, 42-51 (2017).</li><li>Trudel, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+alterations+of+rabbit+Achilles'+tendon+after+immobilization+correlate+with+bone+mineral+density+but+not+with+magnetic+resonance+or+ultrasound+imaging.">Mechanical alterations of rabbit Achilles' tendon after immobilization correlate with bone mineral density but not with magnetic resonance or ultrasound imaging.</a> Archives of Physical Medicine and Rehabilitation. 88 (12), 1720-1726 (2007).</li><li>Harvey, L. 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An experimental longitudinal study in the rat knee.</a> Archives of Physical Medicine and Rehabilitation. 81 (1), 6-13 (2000).</li><li>Chimoto, E., Hagiwara, Y., Ando, A., Itoi, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Progression+of+an+arthrogenic+motion+restriction+after+immobilization+in+a+rat+experimental+knee+model.">Progression of an arthrogenic motion restriction after immobilization in a rat experimental knee model.</a> Upsala Journal of Medical Sciences. 112 (3), 347-355 (2007).</li><li>Ando, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Remobilization+does+not+restore+immobilization-induced+adhesion+of+capsule+and+restricted+joint+motion+in+rat+knee+joints.">Remobilization does not restore immobilization-induced adhesion of capsule and restricted joint motion in rat knee joints.</a> Tohoku Journal of Experimental Medicine. 227 (1), 13-22 (2012).</li><li>Abdel, M. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+joint+contracture+on+the+contralateral+unoperated+limb+in+a+rabbit+knee+contracture+model:+a+biomechanical+and+genetic+study.">Effects of joint contracture on the contralateral unoperated limb in a rabbit knee contracture model: a biomechanical and genetic study.</a> Journal of Orthopaedic Research. 30 (10), 1581-1585 (2012).</li><li>Hildebrand, K. A., Sutherland, C., Zhang, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rabbit+knee+model+of+post-traumatic+joint+contractures:+the+long-term+natural+history+of+motion+loss+and+myofibroblasts.">Rabbit knee model of post-traumatic joint contractures: the long-term natural history of motion loss and myofibroblasts.</a> Journal of Orthopaedic Research . 22 (2), 313-320 (2004).</li><li>Klein, L., Player, J. S., Heiple, K. G., Bahniuk, E., Goldberg, V. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isotopic+evidence+for+resorption+of+soft+tissues+and+bone+in+immobilized+dogs.">Isotopic evidence for resorption of soft tissues and bone in immobilized dogs.</a> Journal of Bone and Joint Surgery. American Volume. 64 (2), 225-230 (1982).</li></ol>

The authors have no disclosures or conflicts of interest to declare.

The rat knee arthrometer was developed to reproducibly and reliably determine the maximum extension of the rat knee following an intervention. Advantages of this device include the consistent generation of torque across the knee joint with a constant arm length and extension force. Another advantage includes the ability to set the torque at a level that allows repetitive testing on the same joint to evaluate the influence of different articular structures on knee ROM, such as muscle, capsule, or ligament. For example, fo...

Having full range of motion (ROM) of the joints is critical for health and well-being1. A loss in joint passive ROM is called a contracture2. Joint contractures may arise from numerous conditions, including prolonged bedrest, paralysis, joint arthroplasty, burns, infection, and neurologic conditions1,3,4,5. A contracture of the knee can be disabling as it accelerates joint degeneration, increases the risk of falls and detrimentally affects a person&#39;s ability to perform basic functional tasks including walking, sitting, and climbing stairs6,7.
Once established, contractures of the knee are difficult to treat, and therefore determining which patients are at the highest risk of developing this condition is essential for prevention and avoidance of contracture-associated morbidity8. Experiments are designed to evaluate 1) the conditions causing or influencing knee joint contractures, 2) the severity of contractures, 3) their temporal progression, 4) the tissues involved in the contracture, 5) their reversibility as well as 6) the usefulness of various preventive and curative interventions on knee joint ROM. For all of these experiments, a valid, objective, precise and reproducible method for measuring the ROM is critical. Other ancillary measures (energy expenditure, histomorphometry, gene expression and protein content) are useful markers to understand the pathophysiology of joint contractures, but the mechanical limitation is what limits the patient and leads to disability. Some of the challenges in this area of research includes the heterogeneous methods by which knee ROM may be tested experimentally, as well as a lack of quantitative data9. The use of a variety of different experimental methods leads to results that are not comparable from laboratory to laboratory. This has led to controversy regarding the conditions (such as immobilization or joint arthroplasty) that cause joint contractures10. An automated method of experimentally measuring joint ROM following an intervention is therefore needed.
Here, we describe a user-independent, valid, precise and reproducible protocol for evaluating the rat knee ROM using a custom-built arthrometer linked to a digital camera to precisely measure the knee ROM in extension. We tested the effect of various periods of immobilization on knee ROM. We then describe the methods for measuring ROM at pre-specified torques on the resulting digital images using fixed bony landmarks. Overall, these methods reliably measure rat knee ROM and provide quantitative data.

<table><tbody><tr><td>Arthrometer</td><td>The Ottawa Hospital Rehabilitation Centre - Rehabilitation Engineering&amp;nbsp;</td><td>N/A</td><td></td></tr><tr><td>Camera</td><td>Canon</td><td>EOS-500D</td><td>Commonly known as EOS Rebel T1i</td></tr><tr><td>ImageJ</td><td>National Institutes of Health</td><td>Version 1.45s</td><td></td></tr><tr><td>Absotbent Underpads</td><td>VWR</td><td>820202-845</td><td></td></tr><tr><td>Dissection Kit</td><td>Fisher</td><td>08-855</td><td>Kit Includes:&amp;nbsp; Forceps: medium points, nickel-plated&lt;br/&gt; &amp;nbsp;Scissors: 1.5 in. (40 mm) blades, stainless steel&lt;br/&gt; &amp;nbsp;Dissecting knife handle: nickel-plated&lt;br/&gt; &amp;nbsp;Knife blades: stainless steel, pack of 3&lt;br/&gt; &amp;nbsp;Dropping pipet: glass&lt;br/&gt; &amp;nbsp;Bent dissecting needle: stainless steel with plastic handle&lt;br/&gt; &amp;nbsp;Straight dissecting needle: stainless steel with plastic handle&lt;br/&gt; Vinylite Ruler 6 in. (15 cm)</td></tr><tr><td>Precision Screw Driver</td><td>Mastercraft</td><td>057-3505-8</td><td></td></tr><tr><td>Scalpel Blades - #10</td><td>Fine Science Tools</td><td>10010-00</td><td></td></tr><tr><td>Screwdriver</td><td>Stanley</td><td>057-3558-2</td><td></td></tr><tr><td>Hex Keys</td><td>Mastercraft</td><td>058-9684-2</td><td></td></tr><tr><td>Universal AC to DC powder adapter</td><td>RCA</td><td>108004951</td><td></td></tr></tbody></table>

using a knee arthrometer to evaluate tissue-specific contributions to knee flexion contracture in the rat

Normal knee range of motion (ROM) is critical to well-being and allows one to perform basic activities such as walking, climbing stairs and sitting. Lost ROM is called a joint contracture and results in increased morbidity. Due to the difficulty of reversing established knee contractures, early detection is important, and hence, knowing risk factors for their development is essential. The rat represents a good model with which the effect of an intervention can be studied due to the similarity of rat knee anatomy to that of humans, the rat's ability to tolerate long durations of knee immobilization in flexion, and because mechanical data can be correlated with histologic and biochemical analysis of knee tissue.
Using an automated arthrometer, we demonstrate a validated, precise, reproducible, user-independent method of measuring the extension ROM of the rat knee joint at specific torques. This arthrometer can be used to determine the effects of interventions on knee joint ROM in the rat.

The amount of knee extension determined for various periods of immobility are summarized for increasing durations of immobility and show that more severe contractures were produced following increasing lengths of immobilization. Representative results using ImageJ are shown in Figure 3.
The ability to measure maximum extension of rat knees in a valid, precise and reproducible, user-independent manne...

Watch this Scientific Journal Video about Using a Knee Arthrometer to Evaluate Tissue-specific Contributions to Knee Flexion Contracture in the Rat at JoVE.com

Using a Knee Arthrometer to Evaluate Tissue-specific Contributions to Knee Flexion Contracture in the Rat

The goal of the protocol is to measure the extension range of motion of the rat knee. The effects of various diseases that increase the stiffness of the knee joint and the effectiveness of treatments can be quantified.

Normal knee range of motion (ROM) is critical to well-being and allows one to perform basic activities such as walking, climbing stairs and sitting. Lost ...

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Medicine

6.6K Views.  Elizabeth Bruyère Hospital. The goal of the protocol is to measure the extension range of motion of the rat knee. The effects of various diseases that increase the stiffness of the knee joint and the effectiveness of treatments can be quantified.

Video: Using a Knee Arthrometer to Evaluate Tissue-specific Contributions to Knee Flexion Contracture in the Rat

Athymic Rat Model for Evaluation of Engineered Anterior Cruciate Ligament Grafts

Anterior cruciate ligament (ACL) rupture is a common ligamentous injury that often requires surgery because the ACL does not heal well without intervention. Current treatment strategies include ligament reconstruction with either autograft or allograft, which each have their associated limitations. Thus, there is interest in designing a tissue-engineered graft for use in ACL reconstruction. We describe the fabrication of an electrospun polymer graft for use in ACL tissue engineering. This polycaprolactone graft is biocompatible, biodegradable, porous, and is comprised of aligned fibers. Because an animal model is necessary to evaluate such a graft, this paper describes an intra-articular athymic rat model of ACL reconstruction that can be used to evaluate engineered grafts, including those seeded with xenogeneic cells. Representative histology and biomechanical testing results at 16 weeks postoperatively are presented, with grafts tested immediately post-implantation and contralateral native ACLs serving as controls. The present study provides a reproducible animal model with which to evaluate tissue engineered ACL grafts, and demonstrates the potential of a regenerative medicine approach to treatment of ACL rupture.

Animal models are important tools for the evaluation of tissue-engineered grafts. This paper presents the protocol for preparing an electrospun biodegradable polymer graft for use in anterior cruciate ligament tissue engineering, as well as a surgical protocol for implantation in a rat model.

Anterior cruciate ligament (ACL) rupture is a common ligamentous injury that often requires surgery because the ACL does not heal well without ...

Bioengineering

A Mini-Invasive Internal Fixation Technique for Studying Immobilization-Induced Knee Flexion Contracture in Rats

Joint contracture, resulting from a prolonged joint immobilization, is a common complication in orthopedics. Currently, utilizing an internal fixation to restrict knee joint mobility is a widely accepted model to generate experimental contracture. However, implanting application will inevitably cause surgical trauma to the animals. Aiming to develop a less invasive approach, we combined a muscle-gap separation modus with a previously reported mini-incision skill during the surgical procedure: Two mini skin incisions were made on the lateral thigh and leg, followed by performing muscle-gap separation to expose the bone surface. The rat knee joint was gradually immobilized by a preconstructed internal fixation at approximately 135&#176; knee flexion without interfering essential nerves or blood vessels. As expected, this simple technique permits rapid postoperative rehabilitation in animals. The correct position of the internal fixation was confirmed by an x-ray or micro-CT scanning analysis. The range of motion was significantly restricted in the immobilized knee joint than that observed in the contralateral knee joint demonstrating the effectiveness of this model. Besides, histological analysis revealed the development of fibrous deposition and adhesion in the posterior-superior knee joint capsule over time. Thus, this mini-invasive model may be suitable for mimicking the development of immobilized knee joint contracture.

Here, we present a protocol to describe a minimally invasive technique for knee joint immobilization in a rat model. This reproducible protocol, basing on muscle-gap separation modus and the mini-incision skill, is suitable for studying the underlying molecular mechanism of acquired joint contracture.

Joint contracture, resulting from a prolonged joint immobilization, is a common complication in orthopedics. Currently, utilizing an internal fixation to ...

Developmental Biology

Rat Model of Adhesive Capsulitis of the Shoulder

This proposal aims to create an in vivo rat model of adhesive capsulitis for researching potential treatment options for this condition and other etiologies of comparable arthrofibrosis. The model includes extra-articular fixation of the shoulder in rats via scapular to humeral suturing, resulting in a secondary contracture without invading the intra-articular space and resulting in decreased rotational ROM and increased joint stiffness.
We used 10 Sprague-Dawley rats for the purpose of this study. Baseline ROM measurements were taken before glenohumeral immobilization. The rats were subjected to 8 weeks of immobilization before the fixation sutures were removed and changes in ROM and joint stiffness were evaluated. To evaluate whether immobilization resulted in a significant reduction in ROM, changes in kinematics were calculated. ROM was measured at each time point in the follow-up period and was compared to the baseline internal and external ROM measurements. In order to evaluate the stiffness, joint kinetics were calculated by determining the differences in torque (text and tint ) needed to reach the initial external rotation of 60&#176; and initial internal rotation of 80&#176;.
After the removal of the extra-articular suture fixation on follow-up day 0, we found a 63% decrease in total ROM compared to baseline. We observed continuous improvement until week 5 of follow-up, with the progress slowing down around a 19% restriction. On week 8 of follow-up, there was still an 18% restriction of ROM. Additionally, on follow-up day 0, we found the torque increased by 13.3 Nmm when compared to baseline. On week 8, the total torque was measured to be 1.4 &#177; 0.2 Nmm higher than initial measurements. This work introduces a rat model of shoulder adhesive capsulitis with lasting reduced ROM and increased stiffness.

This protocol presents an in vivo rat model of adhesive capsulitis. The model includes an internal fixation of the glenohumeral joint with extra-articular suture fixation for an extended time, resulting in a decreased rotational range of motion (ROM) and increased joint stiffness.

This proposal aims to create an in vivo rat model of adhesive capsulitis for researching potential treatment options for this condition and other ...

Evaluation of Stem Cell Therapies in a Bilateral Patellar Tendon Injury Model in Rats

Regenerative medicine provides novel alternatives to conditions that challenge traditional treatments. The prevalence and morbidity of tendinopathy across species, combined with the limited healing properties of this tissue, have prompted the search for cellular therapies and propelled the development of experimental models to study their efficacy. Umbilical cord matrix-derived mesenchymal stem cells (UCM-MSC) are appealing candidates because they are abundant, easy to collect, circumvent the ethical concerns and risk of teratoma formation, yet resemble primitive embryonic stem cells more closely than adult tissue-derived MSCs. Significant interest has focused on chitosan as a strategy to enhance the properties of MSCs through spheroid formation. This paper details techniques to isolate UCM-MSCs, prepare spheroids on chitosan film, and analyze the effect of spheroid formation on surface marker expression. Consequently, creation of a bilateral patellar tendon injury model in rats is described for in vivo implantation of UCM-MSC spheroids formed on chitosan film. No complication was observed in the study with respect to morbidity, stress rising effects, or tissue infection. The total functional score of the operated rats at 7 days was lower than that of normal rats, but returned to normal within 28 days after surgery. Histological scores of tissue-healing confirmed the presence of a clot in treated defects evaluated at 7 days, absence of foreign body reaction, and progressing healing at 28 days. This bilateral patella tendon defect model controls inter-individual variation via creation of an internal control in each rat, was associated with acceptable morbidity, and allowed detection of differences between untreated tendons and treatments.

This paper describes the preparation and evaluation of umbilical cord matrix-derived mesenchymal stem cells spheroids with a bilateral patellar tendon defect model in a rat. This model was associated with an acceptable morbidity and was found to detect differences between untreated and treated tendons, and between the two treatments tested.

Regenerative medicine provides novel alternatives to conditions that challenge traditional treatments. The prevalence and morbidity of tendinopathy across ...

A Non-Invasive Method for Generating the Cyclic Loading-Induced Intra-Articular Cartilage Lesion Model of the Rat Knee

The pathophysiology of primary osteoarthritis (OA) remains unclear. However, a specific subclassification of OA in relatively younger age groups is likely correlated with a history of articular cartilage damage and ligament avulsion. Surgical animal models of OA of the knee play an important role in understanding the onset and progression of post-traumatic OA and aid in the development of novel therapies for this disease. However, non-surgical models have been recently considered to avoid traumatic inflammation that could affect the evaluation of the intervention. 
In this study, an intra-articular cartilage lesion rat model induced by in vivo cyclic compressive loading was developed, which allowed researchers to (1) determine the optimal magnitude, speed, and duration of load that could cause focal cartilage damage; (2) assess post-traumatic spatiotemporal pathological changes in chondrocyte vitality; and (3) evaluate the histological expression of destructive or protective molecules that are involved in the adaptation and repair mechanisms against joint compressive loads. This report describes the experimental protocol for this novel cartilage lesion in a rat model.

Here, we present the cyclic loading-induced intra-articular cartilage lesion model of the rat knee, generated by 60 cyclic compressions over 20 N, resulting in damage to the femoral condylar cartilage in rats.

The pathophysiology of primary osteoarthritis (OA) remains unclear. However, a specific subclassification of OA in relatively younger age groups is likely ...

Development and Evaluation of a Rat Model of Full-Thickness Cartilage Defects

Cartilage defects of the knee joint caused by trauma are a common sports joint injury in the clinic, and these defects result in joint pain, impaired movement, and eventually, knee osteoarthritis (kOA). However, there is little effective treatment for cartilage defects or even kOA. Animal models are important for developing therapeutic drugs, but the existing models for cartilage defects are unsatisfactory. This work established a full-thickness cartilage defects (FTCD) model by drilling holes in the femoral trochlear groove of rats, and the subsequent pain behavior and histopathological changes were used as readout experiments. After surgery, the mechanical withdrawal threshold was decreased, chondrocytes at the injured site were lost, matrix metalloproteinase MMP13 expression was increased, and type II collagen expression decreased, consistent with the pathological changes observed in human cartilage defects. This methodology is easy and simple to perform and enables gross observation immediately after the injury. Furthermore, this model can successfully mimic clinical cartilage defects, thus providing a platform for studying the pathological process of cartilage defects and developing corresponding therapeutic drugs.

This protocol establishes a full-thickness cartilage defects (FTCD) model by drilling holes in the femoral trochlear groove of rats and measuring the subsequent pain behavior and histopathological changes.

Cartilage defects of the knee joint caused by trauma are a common sports joint injury in the clinic, and these defects result in joint pain, impaired ...

Standardized Tuina Manipulation for Knee Osteoarthritis in Rats

Tuina Manipulation to Reduce Inflammation and Cartilage Loss in Knee Osteoarthritis Rats

Clinical trials suggest that Tuina manipulation is effective in treating knee osteoarthritis (KOA), while further studies are required to discover its mechanism. Therefore, the manipulation of animal models of knee osteoarthritis is critical. This protocol provides a standard process for Tuina manipulation on KOA rats and a preliminary exploration of the mechanism of Tuina for KOA. The press and kneading manipulation method (a kind of Tuina manipulation that refers to pressing and kneading the specific area of the body surface) is applied on 5 acupoints around the knee joint of rats. The force and frequency of the manipulation were standardized by finger pressure recordings, and the position of the rat during manipulation is described in detail in the protocol. The effect of manipulation can be measured by pain behavior tests and microscopic findings in synovial and cartilage. KOA rats showed significant improvement in pain behavior. The synovial tissue inflammatory infiltration was reduced in the Tuina group, and the expression of tumor necrosis factor (TNF)-&#945; was significantly lower. Compared to the control group, chondrocyte apoptosis was less in the Tuina group. This study provides a standardized protocol for Tuina manipulation on KOA rats and preliminary proof that the therapeutic effects of Tuina may be related to reducing synovial inflammation and delayed chondrocyte apoptosis.

Author Spotlight: Understanding the Mechanism of Tuina Manipulation in Rats 

We present a protocol for Tuina manipulation performed on plaster-immobilized-induced knee osteoarthritis rats. Based on the preliminary results, it suggested that the efficacy of the method relied on the reduction of inflammation and cartilage loss.

Clinical trials suggest that Tuina manipulation is effective in treating knee osteoarthritis (KOA), while further studies are required to discover its ...

Treating Knee Osteoarthritis with Tuina in a Rabbit Model

Tuina Intervention in Rabbit Model of Knee Osteoarthritis

Knee osteoarthritis (KOA) is mainly characterized by degenerative changes in the knee joint's cartilage and surrounding soft tissues. The efficacy of Tuina in treating KOA has been confirmed, but the underlying mechanism needs to be investigated. This study aims to establish a scientifically feasible KOA rabbit model treated with Tuina to reveal the underlying mechanisms. For this, 18, 6-month-old normal-grade male New Zealand rabbits were randomly divided into sham, model, and Tuina groups, with 6 rabbits in each group. The KOA model was established by injecting 4% papain solution into the knee joint cavity. The Tuina group was intervened with Tuina combined with the knee joint rotary correction method for 4 weeks. Only the standard grasping and fixation were performed in sham and model groups. At the end of the 1-week intervention, the knee joint range of motion (ROM) was observed, and cartilage hematoxylin-eosin (HE) staining was done. The study shows that Tuina could inhibit chondrocyte apoptosis, repair cartilage tissue, and restore knee joint ROM. In conclusion, this study demonstrates the scientific feasibility of Tuina treatment for KOA model rabbits, highlighting its potential application in the study of KOA and similar knee joint-related conditions.

Author Spotlight: Using a Rabbit Model to Explore the Efficacy of Tuina in Treating Knee Osteoarthritis 

The protocol describes a method for Tuina intervention in a rabbit model of knee osteoarthritis.

Knee osteoarthritis (KOA) is mainly characterized by degenerative changes in the knee joint's cartilage and surrounding soft tissues. The efficacy of ...

Establishment of the KOA Model in Rabbits Using the Modified Videman Method

Application of Acupotomy in a Knee Osteoarthritis Model in Rabbit

Knee osteoarthritis (KOA) is one of the most frequently encountered diseases in the orthopedic department, which seriously reduces the quality of life of people with KOA. Among several pathogenic factors, the biomechanical imbalance of the knee joint is one of the main causes of KOA. Acupotomology believes that restoring the mechanical balance of the knee joint is the key to treating KOA. Clinical studies have shown that acupotomy can effectively reduce pain and improve knee mobility by reducing adhesion, contracture of soft tissues, and stress concentration points in muscles and tendons around the knee joint. 
In this protocol, we used the modified Videman method to establish a KOA model by immobilizing the left hindlimb in a straight position. We have outlined the method of operation and the precautions related to acupotomy in detail and evaluated the efficacy of acupotomy in conjunction with the theory of "Modulating Muscles and Tendons to Treat Bone Disorders" through the detection of the mechanical properties of quadriceps femoris and tendon, as well as cartilage mechanics and morphology. The results show that acupotomy has a protective effect on cartilage by adjusting the mechanical properties of the soft tissues around the knee joint, improving the cartilage stress environment, and delaying cartilage degeneration.

Author Spotlight: Investigating the Mechanism of Action of Acupotomy in Treating Knee Osteoarthritis

In this protocol, a knee osteoarthritis model was prepared using the modified Videman method, and the operation procedures and precautions of acupotomy are detailed. The effectiveness of acupotomy has been demonstrated by testing the mechanical properties of quadriceps femoris and tendon and the mechanical and morphological properties of cartilage.

Knee osteoarthritis (KOA) is one of the most frequently encountered diseases in the orthopedic department, which seriously reduces the quality of life of ...

In vivo Measurement of Knee Extensor Muscle Function in Mice

Skeletal muscle plasticity in response to countless conditions and stimuli mediates concurrent functional adaptation, both negative and positive. In the clinic and the research laboratory, maximal muscular strength is widely measured longitudinally in humans, with knee extensor musculature the most reported functional outcome. Pathology of the knee extensor muscle complex is well documented in aging, orthopedic injury, disease, and disuse; knee extensor strength is closely related to functional capacity and injury risk, underscoring the importance of reliable measurement of knee extensor strength. Repeatable, in vivo assessment of knee extensor strength in pre-clinical rodent studies offers valuable functional endpoints for studies exploring osteoarthritis or knee injury. We report an in vivo and non-invasive protocol to repeatedly measure isometric peak tetanic torque of the knee extensors in mice across time. We demonstrate consistency using this novel method to measure knee extensor strength with repeated assessment in multiple mice producing similar results.

Quantification of knee extensor maximal strength is imperative to understand functional adaptations to aging, disease, injury, and rehabilitation. We present a novel method to repeatedly measure in vivo knee extension isometric peak tetanic torque.

Skeletal muscle plasticity in response to countless conditions and stimuli mediates concurrent functional adaptation, both negative and positive. In the ...

Using a Knee Arthrometer to Evaluate Tissue-specific Contributions to Knee Flexion Contracture in the Rat

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