Documenting Quantity and Variation in Patient-Managed Exercise and Activity after Total Knee Replacement

Abstract

Background: Total Knee Replacement (TKR) consistently eliminates pain due to degenerative knee conditions. However, despite a skilled operative procedure and a refined prosthetic, some patients do not achieve expected post-TKR functional gains. Variation in post-operative rehabilitation regimens, including home exercise and general activity, may contribute to variable functional return. Research has not determined optimal physical therapy protocols or ideal patient-managed exercise and activity regimens. To support future TKR rehabilitation research, this preliminary study evaluates patient acceptance and utility of two methods to record patient-managed (home) exercise and activity following TKR. Secondly, analysis of exercise levels and variation in quantity are presented. Methods: Two prospective samples of TKR patients agreed to either (1) complete a daily confidential exercise log documenting sets and repetitions for six standard exercises during post-op weeks 3 through12 or (2) to wear a step activity monitor and record exercise and activity at two time periods: pre-TKR and 6 weeks post-TKR. Analysis of exercise and activity patterns controlled for age, gender and BMI. Results: More than 90 percent of patients successfully maintained exercise logs during the post-TKR period or wore a step activity monitor. The timing of peaks on step activity monitor peaks correlate with patient-recorded log data. However, the majority of sustained intense activity was in addition to the documented home exercise sessions. Significant variation in exercise quantity was documented. Exercise log data showed both within and between patient variation in mean exercise repetitions/day with between-patient variation accounting for 61% of total variance. For example, patients recorded a mean=28 daily sitting knee flexion/extensions (SD=17 between patients). Females report greater between patient variation than males [SD=21 (female) vs. Layeeque 14 (male).] Women with lower pre-TKR emotional health (SF-36, MCS) recorded fewer mean daily repetitions and greater variation across all 6 exercises. Random effects models (adjusted for gender, age, BMI) among women show every unit increase in pre-op MCS corresponds to one repetition increase in exercise (slope (se), 1.00 (0.496), p=0.044). Importantly, among women, higher numbers of exercise repetitions are associated with larger pre-to-6 month improvement in PCS. Discussion: These data support use of patient-reported exercise logs to document quantity and variation in home exercise. In addition, step activity monitors document incremental information about total activity and complement the exercise log. Both exercise and activity varied significantly across patients and preliminary data suggest exercise quantity varies directly with functional gain after TKR. Further research is needed to validate these findings and to clarify the relationship between post-TKR exercise, activity, and ultimate functional gain.