Patellar Tendon Quality and Knee Symptoms in Male Athletes Before the Anterior Cruciate Ligament Reconstruction

Abstract

Background: It is unknown if the quality of the patellar tendon is affected by an anterior cruciate ligament (ACL) injury. ACL deficient patients (ACL-D) have shown to have knee pain, quadriceps weakness and reduced knee function. Ultrasound tissue characterization (UTC) has been used to assess the quality of tendons by quantifying the proportion of echo-types using a numerical grading system from best to worst (I-IV). The primary aims of this cross-sectional study were to investigate the patellar tendon quality in athletes with unilateral ACL injuries, and to compare them to asymptomatic control tendons. The secondary aims were to assess the impact of anterior knee pain (AKP) in the patellar tendons of ACL-D, and to explore possible correlations between tendon quality and knee pain, knee extensor strength and time from ACL injury. Methods: UTC was used to scan both patellar tendons of 81 ACL-D athletes and 20 control tendons. Echo-types distribution was calculated to compare the quality between limbs of ACL-D and control tendons; and to compare ACL-D with AKP, other knee pain, and without pain. Associations between the variables of tendon quality and knee symptoms were explored. Results: No difference in tendon quality was found between limbs of ACL-D. Both tendons of ACL-D displayed more echo-type II at the patellar apex, and same or less echo-types III and IV than controls. The proximal half of the control tendons displayed better quality than the distal half. ACL-D knees with pain displayed less extensor strength, however, in addition to the lack of difference in tendon quality regardless of the presence and location of pain, there was no meaningful association between pain, extensor strength and tendon quality. Nevertheless, there were weak to moderate associations between tendon quality and time from ACL injury. Conclusion: Despite the ACL injury, there is no difference in tendon quality between ACL-D limbs, or when subgrouping ACL-D tendons by presence and location of knee pain. Different areas of the patellar tendon may present different characteristics that might be related to training. Tendon quality is better if a person has longer time from injury.