Recurrent patellar instability: Implications of preoperative patellar crepitation on the status of the patellofemoral articular cartilage

Background: The purpose of the study was to quantify the frequency, severity, and location of patellofemoral (PF) articular cartilage changes recurrent patellar instability treated surgically in patients with preoperative clinical patellar crepitation. Methods: A single-surgeon database was queried for all knees with recurrent patellar instability between 3/2000 and 6/2012 (n=214). Only knees which underwent knee arthroscopy during the surgical treatment were included (n=148). PF articular cartilage condition was assessed arthroscopically. Results: There were 148 knees in 130 patients (mean age, 16 y), which met inclusion criteria. There were 93 females and 37 males. Diagnoses were dislocations [122 (82.4%)] and subluxations (26). Preoperatively 28 knees (18.9%) had PF crepitation. Statistical analysis demonstrated preoperative PF crepitation was correlated with medial patellar facet lesions (P=0.0022) and were 3.6 times more likely to have medial patellar facet lesions. Crepitation was correlated with the higher outerbridge (OB) patellar grades (P<0.0001) and larger patellar lesion size (P=0.0021). At arthroscopy 89 knees (60.5%) had patellar articular cartilage damage with a mean OB grade of 1.3 (0 to 4) and mean size of 93.2 mm ² (0 to 750). The femoral articular cartilage was identified in 29 knees (19.7%) with a mean OB grade of 0.44 (0 to 4). Conclusions: PF articular damage was present in 63% of knees, which were surgically treated for patellar instability. The patella was involved in 61% (mean, 129 mm ² ) and femoral trochlea in 20% (mean 166 mm ² ) of knees. Knee with preoperative PF crepitation (20% of cohort) more commonly had medial patellar facet lesions with higher OB grades, and larger patellar lesion size than knees without preoperative crepitation. Because of the high frequency of patellar (83%) and femoral (36%) articular damage documented at the time of surgical reconstruction, visualization of the PF joint is recommended when knees have preoperative PF crepitation. Level of Evidence: Level IV.