Introduction: Hospital accrediting organizations have recently emphasized the evaluation of and response to postoperative pain as the “fifth vital sign”. However, there are no prospective studies describing normal pain patterns after TKA to guide appropriate clinical responses. Similarly, there are no studies describing those at risk for unusual pain.

Purpose: To outline the pattern of normal recovery and identify factors predictive of significant pain after TKA.

Method: Prospective, observational, single surgeon design. Inclusion criteria: primary, cemented TKA for osteoarthritis. Clinical & radiographic measures obtained pre-op and at 1,3,6 and 12 months post-operatively. Predictive factors and post-operative outcomes included body mass index visual analogue scale (VAS), demographics, physical therapy, and component design, alignment and fixation. Psychometric testing included the Beck Depression Inventory and McGill Pain Questionnaire.

Results: 96 patients, 125 knees (mean age = 66, 55.2% women). Mean VAS at pre-op, 1,3, 6 and 12 month visits were 51.1(SD 23.8), 37.4(21.8), 27.0(22.2), 20.8(20.3), and 18.0(21.0), respectively. significant pain (VAS> 40) was reported by 61.51% of patients pre-op, 41.7% at 1 month, 24.0% 3 months, 16.7% 6 months, and 8.3% 12 months. There were no differences in pain based on the type of anesthesia, weight, age or gender. Preoperative elevated depression, anxiety and pain-related suffering descriptors predicted greater pain during the first 6 months after surgery, but did not ultimately affect recovery. Patients who had greater pain (VAS> 40) used more home and outpatient physical therapy (p=0.25).

Conclusion: Contrary to common beliefs, many patients (22%) still experience significant pain up to six months after TKA, despite absence of clinical or radiographic abnormalities. significant pain (VAS > 40mm) after six months may be indicative of an abnormal pain experience. Preoperative pain, depression and suffering are associated with increased early pain andutilization of therapy.