Keck Sports Medicine Spotlight: ACL Injury


Written by Dr. Seth Gamradt

Dr. Seth Gamradt is a specialist in the field of orthopaedic surgery and sports medicine at the Keck Medical Center of USC. Dr. Gamradt is the Director of Orthopaedic Athletic Medicine for USC Athletics.

Here is the first installment in our new series profiling common athletic injuries as written by our elite team of medical professionals:

Anterior Cruciate Ligament (ACL) Injury

Thumbnail image for Figure1.pngIntroduction

The anterior cruciate ligament (ACL) is a main stabilizing ligament of the knee. It prevents abnormal translation and rotation of the tibia with respect to the femur. The ACL is commonly torn during athletics in sports involving cutting or pivoting (e.g. basketball, soccer, football), but also can be torn in any event that causes an undue rotational force to the knee (twisting injury, collision sports, falls, skiing).


An ACL tear is suspected when an athlete twists the knee and feels a 'pop' in the knee. While the tear can often be diagnosed by using physical exam findings of laxity in the knee, imaging studies are ordered. X-rays are taken to rule out fracture and malalignment of the knee. An MRI is ordered to confirm the ACL tear but also to evaluate the other ligaments in the knee, cartilage and meniscus.


Most tears to the ACL are complete ruptures of the ligament at its midpoint. The intra-articular liquid environment of the knee is a poor environment for ligament healing and therefore tears of the ACL do not heal on their own. Athletes wishing to continue their athletic career will need an ACL reconstruction surgery.

Surgery to 'fix' the ACL is a reconstruction (ligament replacement) rather than a repair of the ligament. A reconstruction of the ligament involves placing a graft across the anatomic site of the normal ACL that runs from the tibia to the femur. A small tunnel is drilled in each bone and a new ligament (the 'graft') is brought into the tunnel and is fixed with screws in the anatomic position of the ACL. The operation is performed through small incisions with the aid of an arthroscopic camera within the knee.

Figure 3.pngRecovery

Rehabilitation after ACL reconstruction is lengthy. In general it follows the timeline below, although there are certain patients who progress more quickly or more slowly.
  • 0-3 weeks: Crutches, brace, range of motion as tolerated, gentle quad strengthening
  • 3-8 weeks: Restore full range of motion, decrease swelling, improve strength, normalize walking
  • 8-16 weeks: Extensive strengthening of the leg
  • 16-18 weeks: Jogging on flat ground permitted, continue strengthening
  • 20-24 weeks: Agility drills added, sport specific training
  • 7-9 months: Return to sport allowed provided range of motion and strength are close to normal.

USC student-athletes recover under the guidance of Russ Romano, ATC head athletic trainer at USC in the John McKay Center, which houses a state of the art athletic training facility. 


The Keck Medical School of USC's sports medicine surgeons are the official doctors of USC Athletics. We provide quality care and expert information for both the weekend warrior and the elite athlete. We provide the highest level of care to patients who suffer from athletic injuries or disorders affecting the shoulder, hip, knee, elbow, ankle and foot. Our highly experienced sports medicine physicians specialize in recognizing, managing and rehabilitating injuries related to sport, exercise or recreational activity. Our orthopaedic surgeons ensure that the latest innovative techniques are available for all patients.

Click here for more information on the Keck Center for Sports Medicine. 

Or contact USC Orthopaedic Surgery by phone: 1-800-872-2273


This is great! Torn labrums also seems to be really common- it would be great if you guys could do an article on those too.

Great article you made.. I would like to read your post very much.. carry on guys

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