Why is my joint replacement hurting?

• There are many different reasons for you to have a painful joint replacement, some of them may be benign and others may be more serious. Below I discuss the various possible causes of painful joint, and what you should do.

Muscle Soreness

• Even with a joint replacement in place, you may still have muscle strains or muscular injuries around the joint replacements. This is a common cause of pain, and often will improve with time, physical therapy, and some over the counter anti-inflammatory medications.

Leg Weakness

• Like with a normal joint, if any muscles in your leg get weak and become imbalanced, they can lead to soreness and pain. Even after a joint replacement, it is important to keep your leg strong. Working with physical therapy and doing exercises on your own at home will help get rid of your pain.

Impingement of Soft Tissue

• Sometimes muscles, tendons or ligaments around the knee or hip joint can get irritated by the new implants, and rub along the implants. Sometimes this goes away with time as the tissues around the joint heal. Other times, these tissues can be “released” using a minimally invasive surgery. And rarely, a revision of a particular implant may be required to avoid any overhanging from the bone.

Nerve Pain

• The nerves around the joints can also be irritated after surgery. This is more common in the acute time after the surgery, especially with surgery using an anterior approach with irritation of a nerve that runs near the incision. This often improves with nerve pain medication (e.g. Lyrica or Neurontin), time as the nerve heals, and can be improved with direct massage and desensitization.

Aseptic Loosening

• Over time, sometimes an implant will become loose. This can happen when an implant is “cementless” and the bone is supposed to grow into the implant or when the implant is “cemented” and stuck into the bone with cement. While we aren’t always able to identify the reason for an implant becoming loose, it usually presents with increasing pain as you get up and get moving, without pain at while resting, and can slowly worsen over time. This usually shows up on x-ray over time as well, or sometimes can be easier seen with a bone scan.

• When an implant is identified as being loose, unfortunately it means that a revision is necessary to replace the loose implant.

Infection

• Despite all the precautions we take before surgery, during surgery, and after surgery, there still remains a 0.5-1% risk of infection for patients undergoing surgery, and may be even higher for certain patients with pre-existing conditions. If this happens, it usually presents with redness around the affected joint, wound opening, drainage, increasing pain, and sometimes systemic symptoms like fevers and chills. When this occurs, it is important to get evaluated immediately. Using blood tests and a sample of fluid from the affected joint, a diagnosis can be made. If an infection is identified, it is important to get this taken care of immediately, which will involve a surgery. Sometimes this surgery may be just a thorough cleaning, other times it is necessary to remove all foreign materials, including the implants, and putting in a temporary joint replacement that gives off antibiotics.

• After the surgery, the patient will require a course of antibiotics through their IV for 6 weeks or longer, and may be on antibiotics for a longer period of time.

• This may also require a separate surgery in the future once the infection is cleared to put in a brand new, long-term joint replacement.

Fracture

• After suffering a trauma or a fall, it is possible for you to break the bone either next to the implant or directly touching the implant. This may occur because there is increased stress where the implant ends/touches the bone, and can represent a point of weakness in the bone, especially when the bones become weaker as patients get older. When the bone breaks, sometimes the implant becomes loose, and other times, the implant remains stable.

• Depending on where the fracture occurs, and whether the implant is stable, sometimes these can be treated with weight bearing restrictions and rest and/or immobilization, other times, these injuries may require a surgery to either replace the damaged or loose implant, or stabilize the broken bone.

Instability

• While a joint replacement involves re-shaping the bone and using new implants, an important part of this surgery is balancing the muscles, tendons and ligaments around these joints to make sure everything is properly aligned and stable. Occasionally, over time, injuries can happen to these structures or muscles can become weaker. For hip replacements specifically, it’s also possible that as you age, your spine becomes stiffer, this can alter the way your hips and spine interact, ultimately putting your hip in positions that are at risk for dislocation. Finally, over time, the artificial cartilage (polyethylene) may actually slowly wear down in hip or knee replacements. This can change the tightly fitting implants of the hip or knee replacement and create more space, allowing motion that shouldn’t be there.

• If your hip replacement has a dislocation, often this is treated by reducing the hip using some form of anesthesia. If this happens multiple times, or there is something damaged that puts you at high risk for this happening over and over again, you may require a revision surgery to fix this instability problem.

• If the knee becomes unstable due to injury to one of the ligaments around the knee, you may require bracing to help the ligament heal, a surgery to fix the damaged ligament or structure, or a surgery to change the implants to specialized implants that repalce the function of the injured structure.

• Finally, if the plastic artificial cartilage wears down overtime, sometimes this needs to be replaced with a new piece of plastic by performing a surgery. This is not common, and usually only happens a long time after your initial surgery. The recovery from this surgery is much faster and easier than the initial knee or hip replacement.

Polyethylene Wear

• As discussed above, as you use your artificial hip or knee to get back to doing everything you love to do, the artificial cartilage can wear down over many years.

• This doesn’t happen to everyone, but when it does, and when you develop either pain or instability, you may require a surgery to change the plastic to a fresh, new plastic insert.