Exploring the clinical course of neck pain in physical therapy: a longitudinal study.

Abstract

To investigate the short-term trajectory of recovery from mechanical neck pain, and predictors of trajectory. Prospective, longitudinal cohort study with 5 repeated measurements over 4 weeks. Community-based physical therapy clinics. Convenience sample of community-dwelling adults (N=50) with uncomplicated mechanical neck disorders of any duration. Usual physical therapy care. Neck Disability Index (NDI), numeric rating scale (NRS) of pain intensity. A total of 50 consecutive subjects provided 5 data points over 4 weeks. Exploratory modeling using latent class growth analysis revealed a linear trend in improvement, at a mean of 1.5 NDI points and 0.5 NRS points per week. Within the NDI trajectory, 3 latent classes were identified, each with a unique trend: worsening (14.5%), rapid improvement (19.6%), and slow improvement (65.8%). Within the NRS trajectory, 2 unique trends were identified: stable (48.0%) and improving (52.0%). Predictors of trajectory class suggest that it may be possible to predict the trajectory. Results are described in view of the sample size. The mean trajectory of improvement in neck pain adequately fits a linear model and suggests slow but stable improvement over the short term. However, up to 3 different trajectories have been identified that suggest neck pain, and recovery thereof, is not homogenous. This may hold value for the design of clinical trials.