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Objective: To study effects of body mass index (BMI) on postoperative outcome in patients with osteoarthritis after total knee arthroplasty (TKA)., Methods: The data of 148 patients with osteoarthritis who underwent TKA from June 2006 to May 2009 in our hospital and had complete follow-up data were analyzed restrospectively, including 29 males and 119 females, ranging in age from 39 to 89 years old, with an average age of 71.2 years old. According to BMI classification standard, all the patients were divided into 4 groups: non-obese group (BMI ≤ 25.0 kg/m2), had 38 patients (45 knees), including 9 males and 29 females, with a mean age of (70.0 ± 8.2) years old; overweight group (BMI 25.1 to 27.0 kg/m2), had 40 patients (48 knees), including 10 males and 30 females, with a mean age of (72.6 ± 7.4) years old; obesity group (BMI 27.1 to 30.0 kg/ m2), had 30 patients (43 knees), including 7 males and 30 females, with a mean age of (70.4 ± 6.0) years old; morbidly obesity group (BMI > 30.0 kg/m2), 33 patients (39 knees), including 3 males and 30 females, with a mean age of (71.7 ± 6.4) years old. The index such as Knee Society Score (KSS), anterior knee pain and patella cartilage damage during surgery were recorded before surgery and at the time of follow-up., Results: Postoperative KSS increased significantly compared to preoperative KSS, and the good rate reached to 97.1%. In the knee score, preoperative KSS and postoperative KSS had no significant differences among the four groups (preoperative P = -0.789; postoperative P = 0.133). However, compared with other groups, obesity group got the lowest preoperative function score (preoperative P = 0.036; postoperative P = 0.225). While the incidence of anterior knee pain was 9.7% (17/175), including 14 grade I and 3 grade II. There were no significant differences in incidence of anterior knee pain among four groups (χ2 = 0.764, P = 0.862). The average BMI of the patients with anterior knee pain was (27.4 ± 3.6) kg/m2, while the others' BMI was (27.5 ± 4.4) kg/m2. There was no statistically difference between two groups (t = -0.061, P = 0.951). There were no significant differences in patella cartilage damage among groups (χ2 = 7.070, P = 0.314)., Conclusion: The KSS increases in all the different groups. Those patients get the benefit from TKA, and the obese patients can receive a similar postoperative outcome as the non-obese ones.

Total knee arthroplasty (TKA) identified as an effective treatment for ultimate knee joint disease can effectively relieve pain, correct deformity, improve knee function and enhance the quality of life of patients. Patient satisfaction has been increasingly considered as an important factor in evaluating the success of primary TKA. Anterior knee pain that usually appears in the region of the anterior knee is a recognized complaint for primary TKA and has a strong impact on the improvement of knee function and patient satisfaction of primary TKA. Accordingly, the relief of anterior knee pain has become one of the primary goals of primary TKA. At present, soft tissue lesions around the patellar caused by patellar maltracking and the elevation of internal pressure in subchondral bone because of the high contact stress of patellofemoral joint are both considered as the mechanism of anterior knee pain. For the past few years,on increasing number of studies have focused on the prevention of anterior knee pain following primary TKA. However, none of the past treatment such as patellar resurfacing, patellar denervation without patellar resurfacing or a mobile-bearing prosthesis has a good and affirmative effect on it. The prevention and treatment of anterior knee pain following primary TKA still is a difficult solved problem. To address this problem, we need further researches about the cause of anterior knee pain, knee joint prosthesis and biomechanics of patellofemoral joint, as well as lots of randomized controlled trials.