While performing a primary TKA in consecutive patients, a constrained insert may be necessary when adequate stability and soft tissue balance are not obtained. In this retrospective study, The investigators aim to identify the prevalence and risk factors that associate with the use of a constrained insert in primary TKA.

Inclusion Criteria:

• primary knee osteoarthritis
• primary total knee replacement

Exclusion Criteria:

• secondary knee osteoarthritis
• revision total knee replacement
• previous knee surgery
• post-traumatic knee
• history of previously infection
• comorbidity;rheumatoid arthritis, connective tissue disease, neuromuscular disease, lumbar spinal stenosis, neuropathy
• severe osteoporosis

consecutive patients underwent primary total knee arthroplasty at our institution