Rabbit Model of Extending Knee Joint Contracture: Progression of Joint Motion Restriction and Subsequent Joint...

Area of Science:

• Orthopedics
• Regenerative Medicine
• Biomedical Engineering

Background:

• Knee contracture, a common complication after joint injury or surgery, leads to significant motion loss.
• Understanding the natural history and molecular mechanisms of joint capsule changes post-immobilization is crucial for developing effective treatments.

Purpose of the Study:

• To establish a rabbit model of knee contracture in extension.
• To investigate the time-dependent progression of motion loss and joint capsule alterations following immobilization.
• To explore the role of transforming growth factor-beta1 (TGF-β1) in the development of knee contracture.

Main Methods:

• Unilateral knee joints of 32 rabbits were immobilized in full extension using plaster casts.
• Knee range of motion was measured, and joint capsules were analyzed histologically.
• Messenger RNA (mRNA) levels of TGF-β1 in anterior and posterior joint capsules were assessed at 2, 4, 6, and 8 weeks post-immobilization.
• A control group of 8 rabbits without immobilization was included for comparison.

Main Results:

• Immobilization led to limited knee range of motion starting at 2 weeks.
• Histological analysis revealed synovial membrane thickening and increased collagen deposition in the joint capsule.
• Elevated mRNA levels of TGF-β1 were observed in the joint capsules, correlating with the progression of contracture.
• These fibrotic changes and motion loss intensified up to 6 weeks and progressed more slowly thereafter.

Conclusions:

• The rabbit model effectively replicates knee contracture development and progression.
• Immobilization induces significant histological changes in the joint capsule, contributing to flexion limitation.
• Elevated TGF-β1 expression is implicated in joint capsule fibrosis and serves as a potential therapeutic target for knee contracture.