Frequency of osteophyte formation at posterior notch of the femur among healthy knees of 40's and 50's

Abstract

Purpose: Our previous study revealed osteophyte formation at posterior notch of the femur detected with MRI was a predictive biomarker for future development of osteoarthritis of the knee (KOA) using data from the osteoarthritis initiative (OAI). We named the osteophyte as hidden osteophyte formation on plain x-ray (HOPX) because conventional antero-posterior, lateral, sky-line x-rays could not detect the osteophyte. In that study, participants with grade 0 or 1 on Kellgren and Lawrence grade (K/L) were divided into two groups and those with HOPX at baseline were highly likely to develop radiographic KOA in 48 months, defined by equal or more than K/L grade 2, comparing to those without HOPX. As a next step to utilize HOPX for mas-screening purpose, we have formulated x-ray technique to detect HOPX and named the technique as HOPX view. The purpose of the present study was to examine the frequency of HOPX among healthy knees of 40's and 50's using HOPX view, which presumably enable us to estimate the frequency of pre-early KOA among healthy knees. Methods: Inclusion criteria for the study were, 1) age from 40 to 59, 2) no knee pain during recent 3 months on both knees, 3) no history of surgeries nor immobilization with a cast, 4) no history of inflammatory joint diseases such as rheumatoid arthritis. Exclusion criteria was pregnancy. Participants received 4 kinds of x-ray examination on both knees (antero-posterior, lateral, sky-line, and HOPX view) to determine KL grade and formation of osteophytes on different locations. Size of osteophytes were scored with osteophyte score of the whole organ magnetic resonance imaging (WORMS). Results: There were 87 female (174 knees) and 11 male (22 knees) participants. The number of male was too small for further study so the only results concerning female participants were presented. Fifty-three were in their 40's and 34 were 50's.1.Frequency of equal or more than K/L 2 knees were 4.7% (5/106) in 40's and 10.3% (7/68) in 50's. Total of 3 participants had bilateral KL II knees and 6 participants were unilateral. KL II knees were excluded in further examination.2.Frequencies of HOPX positive knees were 39.6% (40/101) in 40's and 49.2% (30/61) in 50's when defining score 1 or more of WORMS score as positive whereas 5.9% (6/101) in 40's and 11.5% (7/61) in 50's when defining score of 2 as threshold.3.Aside from HOPX, frequencies of osteophytes formation were high in medial tibial plateau and tibial spine. Osteophytes with the WORMS score of 1 or more were observed in 13.9% (14/101) in 40's and 19.7% (12/61) at medial tibial plateau. Those at tibial spine were 10.9% (11/101) in 40's and 14.8% (9/61) in 50's. Conclusions: KL grade 2 knees already existed in 4.7% (5/106) of knees in 40's and 10.3% (7/68) in 50's without any pain. Although true importance of HOPX view has to be determined by longitudinal study and not by this cross-sectional study, our result implicated high prevalence of knees were at risk in developing radiographic KOA in relatively short period of time in female in their 40's or 50's.