Sometimes it feels like my new knee replacement is hot inside. When I touch the skin on the outside it feels normal. Am I imagining this?

No, many patients report warmth or heat in their replaced knees. It's more likely to happen or to be noticed in the first two years after getting the new knee joint.

Research has shown there are normal knee temperature increases in the knee. Using temperature sensors we know there's a one-degree increase with activity like walking or biking. Many joint implants heat up the synovial tissue around the joint by two to three degrees.

The cobalt-chrome with polyethylene implant has higher temperature increases (five to seven degrees). The rotating hinge knee implant has as much as a nine-degree increase after 40 minutes of activity. This suggests that friction from exercise is not dispersed right away.

Tell your orthopedic surgeon about your symptoms. You may need closer follow-up if the heat continues. There's some concern about the life of the implant, too. Over time the increased heat may prevent new cell growth needed for strong bones around the implant. Bone loss or bone resorption can lead to loosening of the implant.