We’ve known for awhile that local anesthetic and steroid shots can produce side effects for stem cells and cartilage cells. Local anesthetics are a common component of knee steroid shots. We’ve been amazed at the toxicity of one commonly used numbing agent in knee steroid shots called Bupivicane (also known as Marcaine). A recent literature review on the topic I performed for another project was so unbelievable, I thought I had to share these studies. In one study, Chu et al. confirmed a lasting toxic effect of bupivacaine on cartilage cells in an animal joint. A full 6 months after they injected a knee joint with a single usual dose of bupivacaine, cartilage in the treated joints had a 50% lower density of chondrocytes (cartilage cells) compared with cartilage in control joints. Talk about side effects! Think about that for a second. A common numbing agent that gets injected into knee joints everyday because it lasts a little longer than other numbing medicines, was able to wipe out 50% of the cartilage cells by 6 months? Even if it only killed off 5% of the cells that would be equivalent of dropping a nuclear bomb inside the knee joint. How about other numbing medicines like Lidocaine? While this is a bit better than Bupivicane, local anesthetics containing lidocaine are significantly more toxic to mature human joint cartilage cells than a saline injection. How about the most common injection given in the United States for a swollen or painful joint with knee arthritis? Usually doctors will combine a steroid medication with a numbing agent like lidocaine and inject these to control pain and swelling. However, the combination of the steroid shot and local anesthetics has an synergistic adverse effect on cartilage causing serious knee steroid injection side effects. This means that the combination of anesthetic and steroid hits the knee joint cartilage cells harder than simply adding up the negative impact of each component. Another common practice is for pain management doctors to inject steroids and anesthetics into a neck or back facet joint (the small joints found at each spinal level). However, a lab study has now shown that these medications also may hit the cartilage in these small joints as well. The upshot? We abandoned the use of Bupivicane several years ago and will only use low doses of lidocaine. We’ve also stayed away from using any anesthetics around stem cells. This new data has now forced us to get rid of even the lidocaine from our joint injections. We’ve spent hours searching the medical literature for a numbing agent that won’t hurt cartilage and have finally found one. We’ll begin using this new numbing agent in all of our joint procedures next week.