LESIONS OF THE POPLITEUS SYSTEM AND THEIR SIGNIFICANCE FOR KNEE LAXITY

Introduction: Staubli postulated a clinical significance of lesions to the popliteus system because of a 95% incidence in acute and 85.7% in chronic ruptures of the cruciate ligaments. The sparse clinical liter ature on this topic favours conservative or operative treatment as wel l. Objective of the study: What is the significance of isolated lesion s of the popliteus tendon on translational stability of the knee joint ? Material and Methods: The popliteus tendon was severed in six sheep. One gear postop. the knee joints were evaluated by means of x-ray, bi omechanical testing, computed tomography osteoabsorptiometry (CTOAM) a nd micromorphology. Results: There were no pathological findings on x- ray. The simulation of the trauma situation ex vivo showed no instabil ity whereas increased translation and progressive loosening of seconda ry stabilizers was found after one year (posterior and total ap-transl ation, compliance index p < 0.05). The position of the density maxima of the subchondral mineralization are about the same on the operated a nd the non-operated knee joint. All tendons healed macroscopically, bu t micromorphology exhibited a persisting increase of cross-sectional a reas, a low differentiated ultrastructure of the tendon and an increas ed cellularity (p < 0.01). Conclusions: Experimental: 1. intraarticula r, extrasynovial tendons heal spontaneously even within the synovial e nvironment; 2. healing is defective even one year postop.; 3. the post ulate of thee significance of the popliteus system for the stability o f the knee is proven. Clinical: 1. (isolated) lesions of the popliteus go undetected with clinical and instrumented examination; 2. conserva tive treatment eventually results in increased posterior translational instability; 3. this will increase strain and load on the menisci and ACL-reconstructions.