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

Area of Science:

• Orthopedics
• Regenerative Medicine
• Sports Medicine

Background:

• Immobilization leads to joint contracture, limiting range of motion.
• Active exercise is commonly believed to aid remobilization and improve joint function.
• The specific impact of active exercise on arthrogenic contracture post-immobilization remains unclear.

Purpose of the Study:

• To investigate the effects of treadmill walking during remobilization on knee joint range of motion and histopathology in rats after immobilization.
• To determine if active exercise improves or exacerbates immobilization-induced joint contracture, particularly arthrogenic contracture.

Main Methods:

• Rat knee joints were immobilized in a flexed position for 3 weeks.
• After immobilization, rats underwent 7 days of remobilization, either with no intervention (RM) or daily treadmill walking (WALK).
• Range of motion (ROM), histopathology, and gene expression of inflammatory and fibrosis mediators were analyzed.

Main Results:

• Both groups showed improved myogenic range of motion (m-ROM) but worsened arthrogenic range of motion (a-ROM) after remobilization.
• Treadmill walking (WALK group) resulted in smaller a-ROM compared to the no-intervention (RM) group.
• Treadmill walking amplified inflammatory and fibrotic reactions and increased fibrosis-related gene expression (TGF-β1, collagen I & III).

Conclusions:

• While free movement aids myogenic contracture, active treadmill exercise immediately after immobilization can worsen arthrogenic contracture.
• Treadmill walking exacerbates immobilization-induced joint contracture by promoting inflammation and fibrosis.
• Active exercise may not be beneficial and could be detrimental for arthrogenic contracture following joint immobilization.