Corticosteroid Injections Damage Cartilage in Rabbit Models

Corticosteroid Injections Damage Cartilage

Clinicians began to treat a variety of joint conditions with corticosteroid injections around 1950. Since clinical improvement was noted, physicians began to use the injections more frequently. Scientists at the University of Montreal were prompted to study effects of steroid injections on cartilage because of reports that a significant number of patients experienced accelerated the joint damage. Researchers chose the rabbit model to study because the rabbit knee is similar to the human knee and they could be microscopically examined for tissue changes.

The researchers injected 25 mg of hydrocortisone over 2 to 12 weeks into rabbit knees and studied the effect on three major components of the joint: proteoglycans (joint proteins that provide structure and lubrication), collagen (the main fiber in cartilage, provides strength and shock absorption) and chondrocytes (The main cells found in cartilage – chondrocytes produce collagen and proteoglycans). As a control, one group of rabbits received weekly saline injections for 12 weeks.

Saline-injected animals and rabbits receiving 2 to 4 hydrocortisone injections showed no differences in structure when compared to normal controls. Animals who received 8 to 12 hydrocortisone injections showed structural changes in the weight-bearing surfaces of the joint. The results of the study indicated that hydrocortisone joint injections could cause significant changes in the cartilage, and this damage increased as the number of injections increased. There was progressive damage to the structure of the cartilage cells and fissures and cysts appeared in weight-bearing areas of the joint. The most striking finding was the decline of proteoglycans as the number of injections increased. Proteoglycan and protein production decreased to a third of the normal rate. There was also a significant reduction in collagen synthesis.

Scientists attributed the proteoglycan loss to the corticosteroid injections since proteoglycans have a lifespan of about 8 to 10 days. Due to this short lifespan changes produced by an intervention, such as the steroid injections, could be identified in a study of this length. Collagen production was decreased to less than a fifth of the normal rate. Proteoglycan loss can lead to joint stiffness and damage of the collagen fibers at the joint surface. Both these events can explain the observed destruction of collagen fibers and fissuring seen on examination of the weight-bearing surface of the joint.

The scientists suggest that the joint damage experienced after corticosteroid injections occurred in three phases. First, the steroids caused a massive decrease in the production of all the major components of the joint. Secondly, the loss of proteoglycan led to cartilage stiffness. Finally, continued weight-bearing caused the death of cartilage cells, degeneration of the cartilage matrix, and fissuring. As enzymes are released by the dying chondrocytes, a vicious cycle of destruction is perpetuated.

As demonstrated in the study above, corticosteroid injections can be very helpful in symptom reduction for some individuals in small doses. However, using corticosteroid injections in a joint can be detrimental over time.

Corticosteroid Injections Damage Cartilage

Behrens, F., Shephard, N, et al. Alteration of rabbit articular cartilage by intra-articular injections of glucocorticoids. Journal of Bone and Joint Surgery, (1975). 75-A(1): 70-76.