Partial knee replacement 4 months ago -- sudden severe pain and hard lump
My mum had a partial knee replacement at the end of October 2012. Although the pain was very bad, she recovered well, having no problems with the knee replacement.
Yesterday, completely out of the blue, she had a sudden severe pain in her knee whenever she bent it, which went on intensely for about 20 minutes. She couldn't bend the knee at all in that time without being in agony, but it felt okay as long as she kept the knee straight. Then slowly the pain reduced and it got to the point where it only hurt if she bent her knee a little bit -- it felt okay if she bent it completely, and okay if she kept it straight. At the same time, we noticed that a VERY hard lump had appeared at the bottom of the scar on her knee. It was not very large, but very, very hard -- not just like ordinary swelling. The knee didn't feel unstable when she walked on it, but she said it felt like the knee was "grinding" on the inside.
Today she was meant to go for her final checkup with the knee specialist but the hospital phoned in the morning to cancel because the doctor was ill. We live in England so my Mum can't get another appointment with any specialist until she sees her ordinary local GP, and the earliest she can possibly see him is tomorrow, and that's hoping she can get an appointment with him -- it may be even later than that.
Her knee is feeling a lot better. It still feels stable when she stands on it, and the lump at the bottom of the scar has gone down, but she is still in pain from it, and she's worried about it.
Can anyone help? I can't find any helpful information online and I would just like some information about what could possibly be wrong with it to put her mind at rest. Does anyone know if it sounds at all possible that the partial knee replacement has failed?
She is 57 years old (56 when she had the operation) and is otherwise in good health.