Effects of treadmill running and limb immobilization on knee cartilage degeneration and locomotor joint kinematics in rats following knee meniscal transection

Abstract

Objective: This study examined the effects of reduced and elevated weight bearing on post-traumatic osteoarthritis (PTOA) development, locomotor joint kinematics, and degree of voluntary activity in rats following medial meniscal transection (MMT).

Design: Twenty-one adult rats were subjected to MMT surgery of the left hindlimb and then assigned to one of three groups: (1) regular (i.e., no intervention), (2) hindlimb immobilization, or (3) treadmill running. Sham surgery was performed in four additional rats. Voluntary wheel run time/distance was measured, and 3D hindlimb kinematics were quantified during treadmill locomotion using biplanar radiography. Rats were euthanized 8 weeks after MMT or sham surgery, and the microstructure of the tibial cartilage and subchondral bone was quantified using contrast enhanced micro-CT.

Results: All three MMT groups showed signs of PTOA (full-thickness lesions and/or increased cartilage volume) compared to the sham group, however the regular and treadmill-running groups had greater osteophyte formation than the immobilization group. For the immobilization group, increased volume was only observed in the anterior region of the cartilage. The treadmill-running group demonstrated a greater knee varus angle at mid-stance than the sham group, while the immobilization group demonstrated greater reduction in voluntary running than all the other groups at 2 weeks post-surgery.

Conclusions: Elevated weight-bearing via treadmill running at a slow/moderate speed did not accelerate PTOA in MMT rats when compared to regular weight-bearing. Reduced weight-bearing via immobilization may attenuate overall PTOA but still resulted in regional cartilage degeneration. Overall, there were minimal differences in hindlimb kinematics and voluntary running between MMT and sham rats.

Keywords: Computed tomography; Knee injury; Osteoarthritis; Rehabilitation; X-ray motion analysis.

Fig. 1.

Setup of the biplanar high-speed video-radiography system to record rats’ hindlimb kinematics during treadmill locomotion.

Fig. 2.

Representative histology (middle row) and EPIC-μCT (bottom row) coronal sections of the tibial plateau in the sham and 3 MMT groups. Smooth green surface represents the integrity of the tibial cartilage. Cartilage lesions were observed in the 3 MMT rats. Cartilaginous and mineralized osteophytes were observed in the MMT and MMT + EXER rats, respectively.

Fig. 3.

Area of exposed bone due to cartilage defect (A) and the volumes of the anterior (B), central (C), and posterior (D) one third of the remaining medial tibial cartilage in the sham and the three MMT groups. The horizontal bar denotes a significant difference between the 2 groups connected by the bar.

Fig. 4.

Cartilaginous osteophyte volume (A), mineralized osteophyte volume (B), subchondral bone volume (C), and subchondral bone fraction (D) of the medial tibial plateau in the sham and the three MMT groups. The horizontal bar denotes a significant difference between the 2 groups connected by the bar.

Fig. 5.

The 3D joint angles of the hip (A–C), knee (D–F), and ankle (G–I) joints of the surgical hindlimbs in the sham, MMT, and MMT + EXER groups at the mid-stance during treadmill locomotion. The horizontal bar denotes a significant difference between the 2 groups connected by the bar.

Fig. 6.

Changes (i.e., % difference of pre-MMT) in the voluntary daily wheel run time (A) and distance (B) in the sham and the three MMT groups at 2, 5, and 8 weeks post-MMT. A negative % value represents a decrease in voluntary running when compared to pre-MMT running. The horizontal bar denotes a significant difference between the 2 groups connected by the bar.