Abstract
Knee warmth is a common clinical observation following total knee arthroplasty (TKA). This can cause concern that infection is present. The purpose of our study was to establish the pattern of knee skin temperature following uncomplicated TKA. It was a prospective study carried out between 2001 and 2004. A pocket digital surface thermometer was used.
A preliminary study established that the best site to measure knee skin temperature was superomedial to the patella and the best time was 12 noon. Patients with an increased risk of infection and those with a contralateral knee pathology or a previous surgery were excluded. Forty-eight patients fulfilled the inclusion criteria and consented to participate; the skin temperature of operated and contralateral knees was measured pre-operatively and daily during the first six weeks post-operatively. Measurements were also taken at 3, 6, 12 and 24 months following surgery. During the course of the study, patients developing complications of the operated knee or any pathology of the contralateral knee were excluded.
Thirty-two patients completed the main study. Following surgery, systemic and both knees temperatures increased. Whereas systemic and contralateral knee temperatures settled within one week, the operated knee temperature took a longer time. The difference in temperature between the two knees had a mean value of +2.9°C at 7 days. This mean value decreased to +1.6°C at 6 weeks, +1.3°C at 3 months, +0.9°C at 6 months +0.3°C at 12 months and +0.04°C at 24 months. Following uncomplicated TKA, the operated knee skin temperature increases compared to the contralateral knee. This increase peaks at day 3 and diminishes slowly over several months; however, it remains statistically significant up to 6 months.
These results correlate with the findings of previous studies that showed a prolonged elevation of inflammatory markers.
