Extrinsic and intrinsic innervation of the guinea pig knee joint: toward an animal model for manipulative therapy.

Objectives: Besides spinal conditions, knee joint problems are one of the most common ailments of the musculoskeletal system. Problems with the knee can be classified into (1) poor mechanics, (2) traumatic injury, and (3) arthritic changes. All these problems can produce pain.

Preliminary morphological evidence that vertebral hypomobility induces synaptic plasticity in the spinal cord.

Objective: A widely accepted theoretical model suggests that vertebral hypomobility can cause pain and abnormal spinal mechanics because of changes in sensory input from spinal and paraspinal tissues. The purpose of this pilot study was 3-fold: (1) to make a preliminary determination if chronic vertebral hypomobility at L4 through L6 in the rat would affect synaptic density and/or morphology in the superficial dorsal horn of the L2 spinal cord level, (2) to identify relevant outcome variables for future studies, and (3) to obtain preliminary data that would permit estimating an appropriate sample size for future studies.

Methods: Using an established rat model, we fixed 3 contiguous lumbar segments (L4-L6) for 8 weeks with a specially engineered vertebral fixation device.