Abstract
This study aimed to develop a rabbit model of knee contracture in extension and investigate
the natural history of motion loss and time-dependent changes in the joint capsule
after immobilization. We immobilized the unilateral knee joints of 32 rabbits by maintaining
the knee joint in a plaster cast at full extension. Eight rabbits were euthanized
at 2, 4, 6, and 8 weeks after casting, respectively, and the lower extremities were
disarticulated at the hip joint. Eight control group rabbits that did not undergo
immobilization were also examined. We assessed the progression of joint contracture
by measuring the joint range of motion, evaluating the histologic alteration of the
capsule, and assessing the mRNA levels of transforming growth factor β1 (TGF-β1) in
the anterior and posterior joint capsules. After 2 weeks of joint immobilization,
the knee joint range of motion was limited, the synovial membrane of the suprapatellar
and posterior joint capsules was thickened, the collagen deposition was increased,
and the mRNA levels of TGF-β1 were elevated in the anterior and posterior joint capsules.
These changes progressed rapidly until 6 weeks of immobilization and may advance slowly
after 6 weeks. Joint contracture developed at the early stage of immobilization and
progressed over time. The changes in the anterior and posterior joint capsules after
joint immobilization may contribute to the limitation in flexion. The elevated mRNA
expression of TGF-β1 may be related to joint capsule fibrosis and may be one of the
causes of joint contracture.
Keywords
joint contracture - animal model - joint range of motion - joint capsule - rabbit
