I had a knee replacement last year that went very well. They put me on a pain pump to numb the knee. I could get up and get going so much easier without the terrible pain other people told me to expect. Now I hear these pain pumps cause joint damage and shouldn’t be used. Will that affect me too?

A pain pump delivers a continuous, steady low-dose of anesthetic (numbing agent) to the joint. With maximum pain control (for example after joint replacement surgery), patients are able to reduce the amount of narcotics used with each surgical episode. With less pain, they are able to get up, move, and enter into a rehab program sooner. And that is a huge benefit of pain pumps.

There is some new evidence that numbing agents (bupivacaine, lidocaine, ropivacaine) do indeed kill cartilage cells called chondrocytes. Even brief exposure can decrease cell metabolism and cause cellular disruption. The end result is chondrocyte breakdown and self-destruction. This effect of anesthetics on cartilage cells is called chondrotoxicity.

Further study showed scientists that once the thin protective layer of cartilage is destroyed, the number of dead cells increases. More time and further exposure to anesthetic agents are the two main risk factors for chondrotoxicity. And they found that the damage to chondrocytes after contact with anesthetics is permanent. The chondrocytes do not regenerate or replace themselves.

In fact, there is some evidence that the damage done by pain pumps after surgery is similar to changes seen with early osteoarthritis. Scientists are now looking for the reason why anesthetics delivered by pain pumps cause joint cartilage destruction.

Current theories include chemical effects, pH (acid-base balance), and preservatives in the solution used to deliver the agents. There may also be an effect of anesthetics on potassium and calcium that damages the cartilage cell DNA. There’s enough destruction to turn on cell apoptosis (the cell’s suicide cycle).

As you have discovered, the use of postoperative pain pumps is indeed getting a second look. Whereas the joint can quickly clear the effects of a single (local) injection of anesthetics, there isn’t a similar ability with continuous exposure. This new information suggest further study is needed in this area. There is a need to verify these findings and to uncover any long-term effects of pain pumps on joints.