Stiffness following total knee replacement is defined as >15° flexion contracture and/or flexion <75° or, for other authors, arc of motion <70° or 45° or 50°. Alternatively, it could be defined as a range of motion less than the patient needs in order to be able to do what they wish.

The first step in management is to determine the causes: preoperative (history of stiffness, patient-related risk factors, etc.), intraoperative (technical error: malpositioning, oversizing, overhanging, etc.), and postoperative (defective pain management and/or rehabilitation, etc.).

Treatment depends on the interval since replacement and on the type of stiffness (flexion or extension), and should be multidisciplinary (surgery, rehabilitation, pain management).

For intervals less than 3 months, manipulation under anesthesia gives good results for flexion. If this fails, surgery should be considered.

If there was no significant technical error, arthrolysis may be indicated, and is usually arthroscopic. It is technically difficult, but has a low rate of complications. Open arthrolysis allows greater posterior release and replacement of the insert by a thinner model.

In case of malpositioning or oversizing or of failure of other procedures, implant revision is the only option, although the risk of complications is high. After exposure, which is often difficult, the aim is to correct the technical errors and to restore joint-line height and two symmetrical, well-balanced spaces in extension and flexion. A semi-constrained or even hinged implant may be needed, although with uncertain lifetime for young patients in the latter case.

In all cases, the patient needs to accept that treatment is going to be long, with more than the intervention itself (i.e., specific pain management and rehabilitation), and that expectations have to be reasonable as results are often imperfect.

expert opinion.