Anterior Cruciate Ligament

Introduction: The Anterior Cruciate Ligament

Problem: Do gastrocnemius/soleus and hamstring tendon strains change the biomechanics of running in athletes and increase the risk of ACL tears?

Rationale: To determine if multiple witnessed ACL tears post calf strains were a coincidence or if these injuries increase the risk of ligament tears due to a change in biomechanics.

Hypothesis: Gastrocnemius/soleus and hamstring strains increase the risk of ACL tears.

Review of Background The anterior cruciate ligament (ACL) is located deep inside the knee joint and connects the femur to the tibia. It is given the name “cruciate” because it runs in the opposite direction of the posterior cruciate ligament (PCL), forming an “x” or cross pattern.

Fleming et al. performed an experiement, The Gastrocnemius Muscle is an Antagonist of the Anterior Cruciate Ligament, to determine the relationship between gastrocnemius muscle contraction and ACL strain. The participants were 4 male and 2 female subjects who were scheduled for an arthroscopic menisectomy or chondral debridement but had no current or previous ACL injury. The subjects’ ages ranged from 38-56. On the day of each subject’s surgery, the patient was given a spinal anesthetic to relax the muscles of the legs. After the surgery, a differential variable transducer was inserted arthroscopically to measure displacement of the anteromedial aspect of the ACL. A positive value indicated strain and a negative value indicated that no strain was present. The participant’s leg was placed in a fixture to ensure proper knee and ankle flexion. Transcutaneous electrical muscle stimulation (TEMS) was used on the gastrocnemius, quadriceps and hamstring muscles to produce contractions. These muscles were tested because of their potential to strain the ACL. TEMS was set to produce torque of the knee at 5 or 10N at the knee and at least 15N at the ankle. The experiment tested 3 muscle stimulations. The gastrocnemius contraction was executed at 5, 15, 30, and 45 degrees of ankle flexion and the ankle was positioned at either neutral, 10 degrees of dorsiflexion, or 20 degrees of plantar flexion. The quadriceps and gastrocnemius co-contraction, and hamstring and gastrocnemius

In addition, if the quadriceps and gastrocnemius are firing at full strength then there is an increased anterior tibial translation therefore placing increased stress on the ACL because there is not protection from the soleus. Likewise, if there is a hamstring strain then a similar cascade of events will occur. The hamstrings will not fire at full strength which increases shear force on the ACL. If there happens to be both a soleus and hamstring strain then there is very minimal protection to the ACL because neither of the protective muscles are firing at full strength to prevent anterior tibial