Mechanical properties within and beyond the physiological length of the semitendinosus muscle of knee-immobilized rats.

Background: The effects of immobilization on passive muscle mechanical properties are inconsistent between studies. Here, we investigated the mechanical properties of immobilized muscle by obtaining length-force curves within and beyond the physiological muscle-tendon length in a knee-contractured rat model.

Methods: Unilateral rat knee joints were immobilized using an external fixator for up to 21 days.

Effects of Each Phase of Anterior Cruciate Ligament Reconstruction Surgery on Joint Contracture in Rats.

Background: Although anterior cruciate ligament reconstruction surgery is known to cause joint contracture, the mechanisms of this process are unknown. We aimed to assess the effects of transection of this ligament and each phase of reconstruction surgery on contracture formation.

Materials And Methods: Rats were divided into groups according to treatment received: sham (arthrotomy), ligament transection, ligament transection plus bone drilling, and ligament reconstruction.

A rat model of hip joint contracture induced by mono-articular hip joint immobilization.

Background: To elucidate the formation process and therapeutic targets of hip flexion contracture, we developed a rat model of hip flexion contracture induced by hip mono-articular immobilization.

Methods: Kirschner wires inserted into the femur and hip bone were anchored at the hip in a flexed position in the immobilization groups and unanchored in the sham groups for up to four weeks. Age-matched untreated rats were used as controls.

The Natural History of Medial Meniscal Tears in the ACL Deficient and ACL Reconstructed Rat Knee.

Objective: The process of anterior cruciate ligament (ACL) injury-induced meniscal tear formation is not fully understood. Clinical studies have shown that ACL reconstruction (ACLR) reduces the development of secondary meniscal tears, but it is difficult to gain insight into the protective effects of ACLR from clinical studies alone. Using rat ACL transection (ACLT) and ACLR models, we aimed to reveal (1) the formation process of meniscal tears secondary to ACLT and (2) the protective effects of ACLR on secondary meniscal tears.

Formation process of joint contracture after anterior cruciate ligament reconstruction in rats.

Knee joint contracture is often induced by anterior cruciate ligament reconstruction (ACLR). However, the temporal and spatial arthrofibrotic changes following inflammatory events, which occur in parallel with the formation of joint contractures after ACLR, are unknown. This study aimed to reveal: (a) time-dependent changes in myogenic and arthrogenic contractures; and (b) the process of arthrofibrosis development after ACLR.

Morphological and biomechanical adaptations of skeletal muscle in the recovery phase after immobilization in a rat.

Background: Range of motion restriction following immobilization is spontaneously recovered at least in part by remobilization. However, the mechanisms underlying how muscles change with range of motion recovery are poorly understood. This study aimed to reveal morphological and biomechanical changes in the knee flexor semitendinosus muscle that contribute to knee joint contracture following the relief of immobilization.

Three-week joint immobilization increases anterior-posterior laxity without alterations in mechanical properties of the anterior cruciate ligament in the rat knee.

Background: Although knee immobilization may deteriorate the mechanical parameters of the anterior cruciate ligament, such as stiffness and failure strength, it is unknown whether it induces laxity in the whole joint. We examined the effects of immobilization on anterior-posterior joint laxity and mechanical properties of the anterior cruciate ligament, as well as histological and gene expression profiles of the joint capsule in rat knee joints.

Methods: Unilateral rat knees were immobilized using an external fixator.

Nitric oxide synthase inhibitor L-NG-nitroarginine methyl ester (L-NAME) attenuates remobilization-induced joint inflammation.

Shortly after joint remobilization, inflammation is induced in the joint and aggravates joint contracture via subsequent fibrosis. However, the mechanisms involved in remobilization-induced inflammation are not yet fully understood. We hypothesized that joint immobilization followed by remobilization induces hypoxia/reoxygenation, initiating inflammatory reactions through nitric oxide (NO) production via NO synthase 2 (NOS2).

A rat model of arthrofibrosis developed after anterior cruciate ligament reconstruction without rigid joint immobilization.

: Complications including arthrofibrosis have been reported after anterior cruciate ligament reconstruction (ACLR) even under accelerated rehabilitation. To overcome this, we developed an animal model of ACLR-induced arthrofibrosis without immobilization.: Thirteen male Wistar rats were divided into ACL transection (ACLT) and ACLR groups.

Low-Level Laser Therapy Prevents Treadmill Exercise-Induced Progression of Arthrogenic Joint Contracture Via Attenuation of Inflammation and Fibrosis in Remobilized Rat Knees.

We investigated whether the combination of exercise and anti-inflammatory/anti-fibrotic treatment using low-level laser therapy (LLLT) promotes recovery from joint contracture without arthrogenic contracture progression. Rat knees were immobilized for 3 weeks in a flexed position. After fixator removal, rats were divided into no intervention (RM), daily treadmill walking (WALK), and daily treadmill walking and LLLT (W + L) groups.

Active exercise on immobilization-induced contractured rat knees develops arthrogenic joint contracture with pathological changes.

This study investigated the effects of treadmill walking during remobilization on range of motion (ROM) and histopathology in rat knee joints, which were immobilized for 3 wk in a flexed position. After fixator removal, rats were divided into a no-intervention (RM) group and a group forced to walk on a treadmill daily at 12 m/min for 60 min (WALK group). Passive knee extension ROMs were measured before (m-ROM) and after (a-ROM) knee flexor myotomy on the first and last day of a 7-day remobilization period, with m-ROM mainly reflecting myogenic factors and a-ROM reflecting arthrogenic factors.

Accumulation of advanced-glycation end products (AGEs) accelerates arthrogenic joint contracture in immobilized rat knee.

Joint mobility decreases in the elderly and in diabetics, this process is thought to be caused by accumulation of advanced-glycation end products (AGEs). Here, we aimed to elucidate the role of AGEs in joint contracture formation in rat knees. Rats were injected with ribose or saline into the knees twice weekly for 8 weeks.