Natural history of the posterior cruciate ligament-deficient knee.

This paper documents the clinical course of the posterior cruciate ligament-deficient knee. By obtaining an understanding of the natural history of this lesion, the indications for surgical repair, reconstruction, and conservative treatment will be more clearly defined, and the clinician will be able to more critically evaluate the results of both acute repair and reconstruction of this ligament. Forty-three patients with an average interval of 6.3 years (range, one to 37 years) between injury and evaluation were included in this study. Fourteen patients had a straight unidirectional posterior instability and 29 had a combined multidirectional instability. The follow-up evaluation included functional assessment, physical and roentgenographic evaluation, arthrometric laxity measurement, and isokinetic dynametric testing of quadriceps function. Statistical treatment of the data, utilizing both nonparametric methods and logistic modeling, clearly delineated the natural history of the injury to the posterior cruciate ligament (PCL). It was established that the functional outcome can be predicted on the basis of the instability type. Specifically, those knees with PCL disruption without associated ligamentous laxity will probably remain symptom-free. However, when PCL disruption is associated with combined instabilities, a less than desirable functional result will probably occur. Application of logistic modeling to the data demonstrated that the functional result was not due to the type of instability per se, but rather to associated factors, i.e., chondromalacia of the patella, meniscal derangement, quadriceps atrophy, or degenerative changes. A direct correlation has been established between combined multidirectional instability and the occurrence of those associated secondary problems resulting in the patient's complaints and functional disability.(ABSTRACT TRUNCATED AT 250 WORDS)