ACL Tear

synonyms: ACL tear, Anterior Cruciate ligament tear

The anterior cruciate ligament often referred to as the ACL. The ACL is one of the four major stabilizing ligaments in the knee. It functions primarily as a restraint to anterior tibial translation (90%); It is also a secondary restraint to tibial rotation and minor secondary restraint to varus-valgus angulation when the knee is in full extension. The tensile strength of the ACL is 2,150 N and its stiffness is 242 N/mm. Tension forces in the ACL are highest with the knee in full extension. The ACL is composed of Type I collagen (90%) and Type III collagen (10%)

The ACL originates from the lateral wall of the intercondylar notch of the distal femur at its posterior aspect and inserts in an oval shaped area, in the anterior aspect of the tibial plateau between the tibial eminences.

70% of injuries to the ACL ligament result from sports participation. 30% from direct contact and 70% from non-contact injuries. They are common in sports just as football, soccer, downhill skiing and rugby. Non contact injuries occurring while changing direction or landing from a jump.  Patients often feel or hear a "pop" sensation. The knee generally swells within a few hours. Knee range of motion may be limited by pain, hamstring spasm, ACL impingement, or an associated meniscal tear.

Female athletes are more likely to sustain ACL tears though the prepondurance of males involved in sports results in more males actually being injured. Risk Factors for ACL tears include: a small femoral notch width, generalized ligamentous laxity, high body mass index, and female gender.

95% of patients with ACL deficient knees who return to high-level activity will have further damage to their knees including meniscal and cartilage damage with resultant progressive arthritis. Arthritic changes have been shown to progress despite successful ACL reconstruction

Treatment for ACL injuries is dependent on the type of tear as well as the patients activity level. Partial thickness ACL tears that involve less than 50% of the thickness of the ACL often do well without surgery. Patients with complete ACL tears who are involved in cutting sports (football, soccer, basketball) or side-to-side sports (skiing, tennis) or are heavy manual labors generally need their ACL surgical reconstructed. Patients who are not involved in sports and do not do heavy labor often due well without surgery.

Risks of surgery include but are not limited to: Loss of stability / Graft failure, Anterior knee pain / kneeling pain, Stiffness, Painful hardware, Infection, Patellar fracture / patellar tendon rupture, Arthritis:, Arthrofibrosis, Cyclops lesion, NVI (saphenous neuralgia), Complex Regional Pain Syndrome, Hemarthrosis, Neurovascular Injury, Hardware failure, Pain unchanged or worse than before surgery, Stiffness, Incisional scar (cosmesis), Numbness surrounding the incision, Need for further surgery, blood clots (DVT), pulmonary embolus (PE), and the Risks of anesthesia including heart attack, stroke and death. Although complications can occur they are uncommon and most patients are satisfied with their surgical outcomes. You should always discuss any concerns that you have about surgery with your surgeon and ensure that you have a surgeon that you trust and are confident in.

After surgery patients are generally placed in a hinged knee brace 7-21 days post-op. They may weight bear as tolerated with crutches and may discontinue crutches when comfortable, usually @ 2 weeks. Patients follow-up 7-14 days after surgery. The knee brace may be removed when non-weight bearing. Bracing is discontinued when patients have excellent muscle control in the knee, generally at 6weeks.

Typically patients have physical therapy 2-3x per week for 12 weeks.   After 1wk they begin low-resistance stationary bike exercises, quad sets, straight leg raises, early hamstring resistance exercises, and closed-chain exercises with elastic cords. Therapy progress from there until patients are returned to full, unrestricted sports.

In general patients progress as follows:

  • 6wks=stair-climbing
  • 12wks=cleared for all activities except: running on hard surfaces, terminal knee extensions with resistance, and jumping/pivoting sports. 
  • 6months=may do running and terminal knee extensions
  • 8months=if 90% of hamstring and quadriceps strength have been regained and patient has full unrestricted ROM they may return to full, unrestricted sport with functional knee brace.
  • Driving: may drive after 6 weeks for right leg; 2 weeks for left leg.

Approximately 90% of patients who undergo ACL reconstruction achieve restoration of knee stability, patient satisfaction, and return to full activity. ACL reconstruction decreases the risk of future meniscal tear, and improves stability, but its effects on delaying or preventing arthritis are unknown.

Further information about ACL tear can be found at the following sites:

Every person and their particular circumstances are different so the treatment for your shoulder may be different than those discussed above. Please read this information carefully. Write down any questions that you have about your injury and its treatment and discuss them with your surgeon. Working together you and your surgeon will determine the best treatment for you.

Appointments to discuss ACL tears with Dr. Grutter can be made here. If you have continued questions or concerns after seeing your orthopaedic surgeon a second opinion from Dr. Grutter is often beneficial.

Dr. Grutter's offices are located just outside Nashville in Gallatin, Tennessee. Directions to the Gallatin office from Nashville or surrounding areas in Tennessee can be located here. Please contact our office if you are from outside the Nashville, Tennessee area and would like assistance in arranging lodging or transportation for a consultation.