Short-term outcomes for total knee arthroplasty patients with active extension lag

Despite the success of total knee arthroplasty (TKA), quadriceps strength can fail to recover. Active extension lag [quadriceps lag (Q-lag)] is a function of quadriceps weakness. Q-lag presents itself in patients who maintain a full passive range of motion (ROM), but are limited in active extension ROM. Few studies have evaluated the outcomes of post-TKA patients in the presence of post-operative Q-lag. Thus, this study aims to compare: (I) pain scores; and (II) rates of readmission to physical therapy (PT) in TKA patients with Q-lag of ≥15 degrees to patients without Q-lag.

A retrospective review of primary TKA patients between 2013 and 2015 was performed. A total of 150 patients (mean age 63.0 years) with a mean follow-up of 30.7 months were analyzed. All patients received an evidence-based protocol for PT at our institution. Patient readmission to PT was recorded if the orthopedic surgeon wrote an additional prescription for PT intervention following the standard of care following TKA. An independent samples t-test and chi-square analysis was conducted to assess the continuous and categorical variables, respectively.

Fifty-one patients had Q-lag ≥15 degrees and 97 patients had Q-lag <15 degrees. Analysis of mean pain scores between the groups demonstrated a significant difference in mean pain scores (1.9 vs. 3.9; P=0.043). Chi-square analysis demonstrated no significant difference in rates of PT readmission between patients who presented with Q-lag, and patients without Q-lag (23.5% vs. 13.4%; P=0.118).

There was no significant difference in readmission rates; however, patients with Q-lag experienced a clinically significant higher pain level. Since this is the first study of its kind, we suggest further investigations on the effect of Q-lag on patient outcomes following primary TKA.