This study evaluated the difference between the modified subvastus approach in total knee arthroplasty (TKA) and the medial parapatellar approach in terms of the postoperative function of the knees.

From March to December 2002, 40 primary TKAs from 26 patients were divided into two groups by a prospective, randomized, blinded trial. The patients were followed up for more than 1 year. The modified subvastus approach was used in 21 knees, and the medial parapatellar approach was used in the remaining 19 knees. The time of postoperatively active straight-leg raise (SLR), and the range of flexion of the operated knee were assessed at postoperative 10 days, 6 weeks, 3, 6, and 12 months. The degree of the patellar tilt and subluxation was investigated at postoperative 12 months. The data collected was analyzed using a t-test.

The patients with the modified subvastus approach performed active straight-leg raise sooner mean, 0.5 day) than the patients operated on using medial parapatellar approach (mean 2.2 days). Knee flexion was better at post-operative 10 days in the modified subvastus approach group than the medial parapatellar approach group. However, there was no statistical difference after 6 weeks, 3 months, 6 months, and 12 months after surgery. The level of patellar tilt and subluxation was similar in the two groups.

The modified subvastus approach provided the advantage of early postoperative rehabilitation in terms of an earlier active SLR and greater knee flexion at 10 days compared with the medial parapatellar approach. The use of the modified subvastus approach in primary TKA is recommended.