To assess the interval change of the minimal joint space width (MJS) in radiographs of the tibiofemoral (TF) joint and of the patellofemoral (PF) joint with a 2-year follow-up in middle-aged people with longstanding knee pain with or without radiographic osteoarthritis (OA) and to study the precision of the MJS measurements.
In the format of a prospective study of early OA the signal knee in 55 people, 28 men and 27 women (aged 41-57 years, median 50), with chronic knee pain at inclusion was examined with a 2-year interval (median 25 months, range 21-30). The MJS of the TF joint was measured using a flexed PA view in weightbearing and the MJS of the PF joint using an axial view in standing.
The MJS of the TF joint decreased medially by 0.056+/-0.44mm (n.s.) and increased laterally by 0.080+/-0.51mm (n.s.) during the time of observation. In knees with an MJS medially that was less or the same as compared with the lateral compartment, the MJS decreased by 0.14+/-0.38mm (p=0.038) and in a subgroup of these knees, without osteophytes, the MJS decreased by 0.14+/-0.27mm (p=0.018). The MJS of the PF joint decreased by 0.019mm (n.s.) during the time of observation. The coefficient of variation for intra- and interobserver MJS measurements of the TF joint was 1.0 and 1.1% medially and 2.3 and 2.7% laterally, and for measurement error 6.9% medially and 4.8% laterally, respectively. The coefficient of variation for intra- and interobserver MJS measurements of the PF joint was 8.1 and 5.8% medially and 7.5 and 10.1% laterally and for the measurement error it was 8.1% medially and 8.5% laterally, respectively.
A statistically significant reduction of the MJS was only demonstrated in the medial compartment of the TF joint in those individuals who had an MJS in this compartment which was less or the same as compared with the lateral compartment as well as in a subgroup of these knees without osteophytes. The radiographic examinations and the MJS measurements were reproducible.