At the standard follow-up moment one year after primary TKA for gonarthrosis, all patients will be checked for signs of fibrosis diathesis. This will be done by examining their hands for Dupuytren's nodules and contractures and recording risk factors associated with increased severity and risk of recurrence of Dupuytren's contracture. These include family history, bilateral DD, and ectopic lesions, age of onset less than 50 years, male gender, Ledderhose disease, first ray involvement, multiple ray involvement and ectopic fibromatosis.

This way, two groups of patients will be identified: those with and those without signs of fibrosis diathesis. For both groups, the range of motion (ROM) of the operated knee at 3 and 6 months will be retrieved in the charts, the ROM at 12 months will be measured at that time. Also, additional procedures performed to increase ROM postoperatively will be retrieved from the charts (e.g. continuous passive motion, mobilization under anesthesia). Other causes for knee stiffness will have to be recorded, since these will be the most important exclusion criteria.

In the patients with clear signs of finger contractures, any impression of increase of contracture over the past 12 months will be recorded.

Inclusion Criteria:

• All patients undergoing a total knee replacement for primary gonarthrosis with a minimum follow-up of 1 year

Exclusion Criteria:

• Patients undergoing a TKA for other reasons than primary gonarthrosis, e.g. after infection, posttraumatic arthritis,hemophilia,…
• Patients who had other problems after their TKA resulting in knee stiffness, e.g. infection, bleeding,…

All patients who undergo a total knee arthroplasty for primary gonarthrosis at a minimal age of 50 years showing signs of fibrosis diathesis at presentation can be included. Patients who do not show signs of fibrosis diathesis will serve as a control group.