Patellar 'entry' feature: a new arthroscopic anatomic finding

The purpose of this paper is to report a frequently noticed anatomical feature on the soft synovial floor of the suprapatellar pouch in the knee, which has not been reported before. Four hundred and fifty-seven consecutive knee arthroscopies were carried out. The patellar entry feature was present in 294 and not noticed in 163. There was not a concurrent control group. During arthroscopy the presence or absence of the patellar entry feature was noted and entered on a database consecutively and prospectively. All arthroscopies were carried out by the senior author. The ages of the patients undergoing arthroscopy ranged from 8 to 96 years with a mean age of 39.4 years. Out of 457 there were 318 males and 139 females. Where the patellar entry feature was found, there was an average of 40% female; where there was not, there was an average of 27% female. The patellofemoral articulation has been a focus of interest mainly because of the poorly understood and extremely common anterior knee pain syndrome (AKPS). We hypothesise that the patellar entry feature is the area where the patella rests, with the knee in full extension and the quadriceps relaxed and is thus the starting point before flexion is initiated.