To observe the incidence of skin sensory loss after total knee arthroplasty (TKA) and its natural history over time, and to identify the  relationship between numbness area and incision length, tourniquet time, age and gender.
In the study, 132 patients (20 males and 112  females, with an average age of 69.75 years old, 135 cases of TKA) who underwent primary TKA with midline incisions were chosen and grouped  chronologically (4 years, 3 years, 2 years, 1 year, 6 months, 1 month) to the investigation time point from Peking University First Hospital. All the operations  were done by the same surgeon team with Stryker NRG and Depuy RP (without patellar resurfacing). Numbness incidence, numbness area, scar length,  tourniquet time were recorded from the questionnaires sent to the patients and their medical records.
84.44% of the patients received a reduced  skin sensory after TKA, 91.22% of which had a smaller numbness area gradually over time. The numbness area was decreased from the 1 month postoperation group to the 4 years postoperation group (P <0.001). The numbness area in 2 years postoperation group and more were significantly smaller  than 1 month postoperation group (P=0.042, 0.004, 0.022), however, the skin flap numbness area had little change after 2 years (P>0.05). The  hypoesthesia flap was completely lateral to the incision in 88.60% of the patients, and the numbness area covered the lateral skin and part of media skin to  the incision in 11.40% of the patients. Numbness size had no relationship with the patients' gender, age, length of scar and tourniquet time (P>0.05).
Most but not all the patients have a dermal hypoesthesia after total knee arthroplasty. The numbness area will gradually reduce over time.  Numbness size is obviously smaller 2 years postoperation and then it will be stable. Gender, age, length of incision, and tourniquet time have no  significant relationship with the size of numbness.