The connection between femoroacetabular impingement (FAI) and osteoarthritis (OA) continues to be a topic of debate for both clinicians and biomechanists. The study by Chinzei et al. adds additional fuel to that conversation in the form of a head-to-head comparison of cartilage tissues taken from patients with FAI and OA. Real-time qRT-PCR (quantitative reverse transcription polymerase chain reaction) results from the comparison indicated that cartilage samples from the FAI samples were more actively engaged in responding to inflammation and degeneration than were the OA tissues, and that the response was dependent on the degree of mechanical impingement. The reverse was found to be true for synovial and labral tissues.

The interpretation of the authors’ results is limited by the lack of the inclusion of “normal” cartilage tissue samples to serve as a comparison group. This limitation is not unique to the work of Chinzei et al.; for obvious ethical reasons, it is unreasonable to extract tissue samples from well-functioning joints. The short window of post-mortem cell viability usually precludes real-time qRT-PCR analysis of cadaveric specimens, and gene-expression results from cultured cells are likely to vary from cells in an in vivo environment because of mechanical and environmental factors.

Another challenge to establishing the link between FAI and OA is due to the disparity in the typical age of onset. FAI has a notably earlier onset age (for example, in the study by Chinzei et al., the average age of the FAI group was forty-two years, whereas it was sixty-nine years for the OA group). While this anecdotally suggests disease progression, it prevents establishing equivalently aged comparison groups for the RT-PCR studies.