I had a strange experience in the hospital after my total hip replacement. They used a nerve block that was supposed to help control the pain during therapy. But my knee kept buckling underneath me. It was like I just couldn’t feel it and make my leg support me. The therapist finally put a knee immobilizer on me until the effect wore off. Does this happen very often? What was the problem with me?

Nerve blocks are somewhat new in the postoperative management of pain after total hip replacements. The idea is to block sensation to the nerve to the hip muscles. With less pain, you’ll feel more like moving, and that’s an important key to a quick and successful recovery.

But the injection of a numbing agent around the nerve can also affect motor function of the nerve to the muscles. The result may be an inability to contract the muscles used to hold the leg straight. The patient ends up with a problem (and solution) that’s similar to yours.

This doesn’t happen very often and hasn’t been reported in the literature yet. But surgeons are taking these kinds of effects into consideration when using nerve blocks. Different protocols are being tried such as a single injection of a numbing agent that lasts a short time versus a continuous delivery of the same numbing agent over a 12-, 24-, or 48-hour time frame.

With a successful nerve block, the physical therapy program can move total hip patients along faster. Studies comparing one daily physical therapy session versus two sessions have been suggested. It’s possible that with a more aggressive rehab program, patients can recover faster and leave the hospital sooner, thus cutting costs even more.