Clinical classification of patellofemoral pain and dysfunction

The patellofemoral joint is a complex articulation based on its dependence on both dynamic and static restraints for stability. Classification of patellofemoral disorders has been frought with confusion. However, progress has been made in the classification and understanding of these disorders by improved understanding of the biomechanics of the joint and by clarification of the terminology to describe patellofemoral pathology. The term chondromalacia patella, although once used as an all-inclusive term for anterior knee pain, is now widely accepted as a term used to describe pathologic lesions of the patellar articular cartilage found at arthroscopy or arthrotomy. An adequate classification system should aid in proper diagnosis and treatment of specific problems. If properly devised, it should also aid in the comparison of results between different treatment centers. In addition, it should be a system that is simple and useful in the clinical setting with minimal use of complicated imaging techniques. From a clinical perspective, patellofemoral problems in the skeletally mature patient fall into three broad categories: 1) patellofemoral instability, i.e., subluxation or dislocation; 2) patellofemoral pain with malalignment but no episodes of instability; and 3) patellofemoral pain without malalignment. The myriad of patellofemoral disorders then fall into subclassifications of these categories. Treatment algorithms can be broadly developed based on the general category, with specific treatments based on the subclassification. In this paper, the authors will present a review of the pertinent literature documenting patellofemoral classification systems and develop concepts of clinical classification of patellofemoral disorders based on the three categories described above.