Following knee surgery, especially after anterior cruciate ligament (ACL) reconstruction, a small percentage of patients complain about significantly decreased patellar mobility accompanied by anterior knee pain, sometimes severe. The limited mobility and knee pain usually do not disappear even with aggressive physical therapy. Arthroscopic exploration of these knees reveals a closure of the patellar tendon-tibial (PTT) interval, i.e., severe fibrous adhesion of the patellar tendon to the anterior aspect of the tibia, the formation of fibrous tissue between the quadriceps tendon and the femur, and a ‘closed-off’ suprapatellar pouch. Other investigators have also noted such adhesion (Paulos et al., 1987 & 1994; Jacobson et al., 1989), and Hughston (1985) attributed the tendon adhesion to the scarring of infrapatellar and suprapatellar fat pad caused by the surgery. While the adhesions are important clinical problems associated with knee surgery, no study to date, other than our experimental study on patellar tendon contracture, has quantitatively investigated the effect of these adhesions on knee kinematics and contact forces (Ahmad et al., 1997). In this study, we use a 3-D mathematical model of the knee joint to analyze the effects of the patellar tendon adhesion (PA) to the anterior tibia, and the quadriceps tendon adhesion (QA) to the anterior femur. Our objective, therefore, is to demonstrate the effects of these types of post-operative adhesions on patellofemoral joint mechanics.