Diabetes with hyperlipidemia: a risk factor for developing joint contractures secondary to immobility in rat knee joints?

Several studies have reported that diabetes may cause limited joint motion and often combines with hyperlipidemia (HL). This study clarifies that joint contracture can be produced by diabetes, HL, or both. The experimental animal model, a rat with diabetes and HL, was developed by streptozosin injection and addition of 1% cholesterol to the food. One hindlimb each from the diabetes group, the HL group, the combined diabetes/HL group, and the control group was immobilized for 2, 3, or 4 weeks in the Phase I study. Diabetes/HL rats were used 4 weeks after immobilization in a Phase II study. Joint motion, elasticity of the knee joint capsule, and contractile function of the gastrocnemius muscle were measured. Gastrocnemius muscle was observed histologically by H&E and ATPase staining. Limited joint mobility was observed 4 weeks after immobilization only in the diabetes/HL group. The intraarticular pressure from the saline injection was lower, and the contractile function of the gastrocnemius muscle decreased in this group. Atrophy of type II fiber was observed in the gastrocnemius muscle. This restriction of joint mobility may depend on skeletal muscle degeneration around the joint rather than on an intraarticular lesion.