Effect of Preoperative Flexion on Postoperative Flexion and Subjective Outcomes after TKA

For those who have total knee arthroplasties (TKA), there are several indicators to determine satisfaction rates for both clinicians and patients. One of the most reported outcomes is flexion range of motion. At the Shelbourne Knee Center, every patient goes through some level of physical therapy prior to their TKA with an emphasis on range of motion, including flexion, as well as improving their overall strength and function. Many patients improve enough that they choose not to have surgery. However, those who, despite improvements, aren’t satisfied with how their knee feels or functions usually proceed with surgery. Our opinion has always been that doing the preoperative physical therapy to improve flexion range of motion helped to improve the patient’s postoperative subjective outcomes, but was this just an opinion—or was it a fact?

This past year, one of our physical therapists and our research staff looked at this data to determine an answer. They wanted to know if the postoperative Knee Injury and Osteoarthritis Score (KOOS) would be higher based on postoperative flexion range of motion and based on their improvement over time. They looked at patients between 2012 to 2021 who underwent a TKA by the same orthopedic surgeon and who were enrolled in our longterm follow-up study. There were 319 patients with complete data for flexion range of motion and KOOS scores taken preoperatively and at 1 year postoperatively. These patients were put into 3 groups based on their preoperative range of motion: low (<120 degrees), average (120-134 degrees) and high (≥135 degrees). The mean change in flexion range of motion for each group was calculated and they determined the percentage of patients within each group who achieved the same, better or worse range of motion after surgery.


The results showed that within each group, those who improved their flexion from preoperative to 1 year postoperative showed higher KOOS scores when compared to those who got worse or stayed the same; however, this difference never reached statistical significance. On average, patients improved knee flexion from preoperative to 1 year, going from 122 degrees to 129 degrees, p<.001. Those in the preoperative flexion groups of low, average,and high were able to increase their 1 year postoperative flexion to a mean of 120 degrees, 130 degrees and 137 degrees, respectively.

There were 62% in the low preoperative flexion group who improved to at least the average flexion group postoperatively. Sixty-three percent of those in the average flexion group preoperatively stayed in this group after surgery while 29% of this group improved and moved into the high flexion group after surgery. The vast majority of the high flexion preoperative group stayed in this group after surgery (76%).

When they looked at the results of the KOOS scores, those in the high postoperative flexion group showed statistically significantly higher 1 year postoperative KOOS scores when compared to those in the low postoperative flexion group (86 compared to 81 with 100 being the highest score; p=.037).

Key Takeaways

So, why is this important information for patients and clinicians? We have found that patients who achieve higher degrees of flexion range of motion after surgery had statistically significantly higher subjective scores compared with those who had lower degrees of flexion. Patients who can improve their range of motion from preoperative to postoperative had better subjective scores compared to those patients that remained in the same group or got worse. Patients should be educated on the importance of maximizing their range of motion prior to their TKA procedure in order to increase the likelihood of attaining similar or better range of motion postoperatively and thus achieving better long term subjective outcomes.

This is one of the benefits of the Shelbourne Knee Center; everything we do is based on fact and not an opinion. Very few, if any, orthopedic surgeons collect long term data on their patients to know answers to patients’ questions and to know if what they are recommending is best practice. We encourage second opinions prior to consenting to any surgery. Once a surgery is done, it cannot be taken back!