Introduction: This biomechanical study evaluates the consequences of a mid-third BPTB-autograft excision on patellofemoral biomechanics and knee kinematics. Of particular interest was the potential role of a BPTB-autograft excision on postoperative anterior knee pain in ACL replacement surgery.

Methods: Isokinetic knee extension from 120 of flexion to full extension was simulated on 9 human knee cadaver specimens (5 male, 4 female, average age at death 43 years). Joint kinematics was evaluated by ultrasound sensors (CMS 100TM, Zebris, Isny, Germany), and retro-patellar contact pressure was measured using a thin-film resistive ink pressure system (K-ScanTM 4000, Tekscan, Boston). All data were taken before and after excision of a mid-third BPTB-autograft.

Results: Following excision of a mid-third patella tendon autograft we found a significant (p< 0.05) proximalization of the patella (average: 0.5 mm) and a significant decrease of patella flexion in the sagittal plane (average: 1). Patella tilt, -rotation (frontal plane), -translation (medial/lateral) and tibiarotation (external-/internal), -axis (varus-/valgus position) remained unchanged. Patellofemoral contact pressure and -area decreased significantly near knee extension (p< 0.05).

Conclusions: We conclude that an excision of a mid-third patella tendon autograft results in a lengthening of the tendon with a proximalization of the patella. As the patellofemoral pressure decreases and the patella remains centralized, postoperative anterior knee pain following ACL-replacement using a BPTB autograft can not be explained by the results of our study.

Purpose: The study was designed to evaluate the biomechanical and neurohistological properties of the infrapatellar fat especially concerning its potential role in the anterior knee pain syndrome.

Methods: Isokinetic knee extension from 120 of flexion to full extension was simulated on 10 human knee cadaver specimens (6 male, 4 female, average age at death 44 years). Joint kinematics was evaluated by ultrasound sensors (CMS 100TM, Zebris, Isny, Germany), and retro-patellar contact pressure was measured using a thin-film resistive ink pressure system (K-ScanTM 4000, Tekscan, Boston). The infrapatellar tissue pressure was analyzed using a closed sensor cell. The patellar contact pressure was measured before and after resection of the infrapatellar fat pad. The distribution of nerve fibres in the infrapatellar fat pad was assed immunohistologically in a second part of the study.

Results: Infrapatellar tissue pressure significantly increased during knee extension < 20 and flexion > 100 ranging from 343 (223) mbar at O- to 60 (64) mbar at 60 of flexion. Total resection of the infrapatellar fat pad resulted in a significant decrease in tibial external rotation of 3° in full knee extension (p=0.011), combined with a significant medial translation of the patella between 29 and 69° knee flexion (p=0.017 to 0.028). Retropatellar contact pressure was significantly (p< 0.05) reduced at all flexion angles, at 120° knee flexion more than in full knee extension. Studying all the detectable nerves present in 50 fields (x200 objective) we found an average of 6.4 substance-P- (25%) of a total of 24.7 nerve fibres in the infrapatellar fat pad. There was a significantly (p< 0.01) higher number of substance-P-fibers (24.4 (28%) of 105.7) in the superficial synovial tissue. The number of S-100-fibers was significantly (p< 0.05) higher in the central and lateral part of the fat pad.

Conclusions: Based on these results, we conclude that resection of the infrapatellar fat pad could potentially reduce clinical symptoms in the anterior knee pain syndrome, and that, contrary to commonly believed, the infrapatellar fat pad may have a biomechanical function and play a role in the anterior knee pain syndrome.

Aims: This biomechanical study was performed to evaluate the consequences of a total infrapatellar fat pad resection on knee kinematics and patellar contact pressure. Methods: Knee motion between 120∞ of flexion and full extension was performed in a knee kinemator on 10 fresh frozen knee specimens (6 male, 4 female, average age 44 years). The joint kinematics was evaluated by ultrasound sensors (Zebris-system), the patellar contact pressure was measured using a thin-film resistive ink pressure system (Tekscan). All data were taken before and after resection of the infrapatellar fat pad and statistically analyzed. Results: A total resection of the infrapatellar fat pad resulted in a significant (p< 0,05) decrease of the tibial external rotation in knee extension combined with a significant (p< 0,05) medial translation of the patella. The patellar contact pressure was significantly (p< 0,05) reduced, in knee flexion more than in knee extension. Conclusions: We conclude that a resection of the infrapatellar fat pad might reduce clinical symptoms in the anterior knee pain syndrome. A biomechanical function of the infrapatellar fat is suspected.