ACL Repair Prognosis

author : AMSSM
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Sports Doc gives advice on recovery

Member Question:
I recently had an acl repair, and had to have about 50% of my lateral meniscus removed.

I'm an avid ultra distance runner, but my surgeon now suggested I choose another sport.

Don't think I'll struggle to get back to activity now, but am more worried about the longterm consequences. There' s not much good data available of longterm outcomes, although people with these injuries are at risk of earlier osteoathritis and knee replacement.

Answer by Caitlyn Mooney, MD
Member AMSSM

Thank you for submitting your question. Your conundrum is certainly difficult and one that injured young athletes have a hard time answering.   As you know knee injuries place athletes at increased risk of knee arthritis.   Athletes are left trying to determine whether they should continue to participate in the activities that they love or change to new ones with less joint impact after a major knee injury. Oftentimes athletes have a hard time giving up a sport they enjoy even after onsets of symptoms related to arthritis.   There is no correct answer for this but I hope that this article will help you understand the connection between knee injury and arthritis.  

For background: The knee joint is made up of the tibia (shin bone of the lower leg), the femur (large bone of the thigh), and the patella (knee cap). In a healthy knee joint, the tips of the bones which come into contact with each other in the joint are lined with articular cartilage. Articular cartilage is a smooth cartilage surface and allows for the gliding motion of the joint. It protects the bones and provides some cushioning.  

The knee also has additional soft tissue.   There are many ligaments including the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL).   These along with other soft tissues such as other ligaments, tendons, and connective tissue provide stability for the knee joint. The ACL which provides the majority of the the restraint of forward displacement of the shin bone is most commonly injured by either landing from a jump or pivoting/ changing direction. Without an intact ACL, athletes may develop instability of the knee which can result in damage to additional structures including the knee’s articular cartilage.   It can also make it difficult to do sports or even daily activities.   When someone tears their ACL the decision to reconstruct it with surgical intervention depends on the age, activity level, instability of the joint, and additional injuries such as meniscus.   The decision to reconstruct and which type of graft to use is an important one to be determined between an athlete and their surgeon. There is a tendency for young and active patients to undergo reconstruction due to activity level as well as concern for further damage to the knee joint. Repairing the ACL can improve stability in the joint especially for those who desire to do sports with jumping and pivoting.   Additionally, it is felt that by repairing the ACL that there is less risk of subsequent damage to the the meniscus as a damaged meniscus also increases one’s risk for osteoarthritis. There remains controversy and some differing of opinion as to what degree, if any, ACL reconstruction can prevent subsequent osteoarthritis.

Additionally, there are other tissues in the knee including the two meniscus which act as cushions between the thigh bone and the shin bone. These help absorb shock and minimize force transmission to the bone and cartilage. These can be commonly torn when the knee is twisted.   A tear can result in swelling, inability to bend or straighten the knee fully, knee pain, and other symptoms. There are also degenerative meniscus tears which can occur spontaneously in older people. Generally surgical intervention is attempted with acute or sudden meniscus tears in the young. There are two options for surgical intervention. One is to repair the torn portion of the meniscus with sutures. Due to the poor vascular supply of the meniscus, however, this is not always possible and even if attempted the tear can recur or not fully heal.   If repair is not possible a portion of the meniscus or whole meniscus may be removed. Meniscus tears can lead to altered joint loading which can overload the surrounding tissues including the cartilage underneath over time.

Arthritis is inflammation of the joint and involves the wearing away of the articular cartilage, injury to the underlying bone, and degenerative changes to surrounding structures. Eventually the bones of the joint may be in direct contact with each other with no overlying articular cartilage. There are multiple types of arthritis with the two most common being osteoarthritis and rheumatoid arthritis. Osteoarthritis which is the most common chronic joint disease is caused by wear and tear on the joint over time is also known as degenerative joint disease. The most common symptoms of osteoarthritis are joint pain which can worsen after activity, joint swelling, and joint stiffness. Osteoarthritis is progressive and the joint continues to wear over time.   There is a subset of osteoarthritis called post traumatic-arthritis. While similar in many ways, post-traumatic arthritis is different from regular osteoarthritis in several ways. First off the patients are younger and may present in 20s-40s.   Additionally, the progression in post-traumatic arthritis is more rapid. Thus since many people who sustain traumatic knee injuries do so when they are younger, there are young adults dealing with the pain and disability of arthritis. Post- traumatic arthritis can present after a variety of knee injuries but is common after ACL and meniscus injuries. It is also common after fractures that extend to the knee joint.

One study demonstrated that after ACL and meniscus injuries 50% had had pain or functional impairments associated with arthritis 10-20 years after injury. The reason for this is multifactorial: first there are several factors that promote arthritis even at the time of initial injury. Depending on the initial injury, articular cartilage and underlying bone can be fractured or have microscopic injuries which can lead to focal or widespread damage to the hard tissues of the joint. Blood and inflammatory mediators (cells, proteins, and enzymes that promote inflammation in the joint) are set loose in the knee joint during a severe knee injury which can injure or kill the cells that make up the cartilage throughout the knee joint.   This damage can lead to permanent sequelae long-term.

In addition to immediate damage at the time of injury, both meniscus and ACL injuries alter the mechanics of the knee. These mechanical changes aren’t all corrected by reconstructive surgery or repair. The altered mechanics change the wear patterns of the joint as well as change the way load is transmitted throughout the tissues. All of these can alter force dissipation in the knee joint which may cause too much force to go through small areas of the articular cartilage or even to different tissues such as the cartilage and bone throughout the knee which were are not built to absorb all of the impact of the knee. Some additional factors that impact knee mechanics after surgery are changes in one’s posture, proprioception, gait, and muscle strength which also can alter wear on the joint.

Thus as you can see there are many factors that occur at the initial time of injury or in the following years that can increase your chances of developing arthritis once injuring your knee. While there is about a 5x increased risk of developing knee arthritis if you had a severe knee injury, having a knee injury does not guarantee you will develop arthritis. Also, even if you alter your activity there is not a guarantee that you will not develop symptomatic arthritis.  There are other factors that also impact risk such as family history, age, sex, obesity, activities, re-injury, and the individual mechanics of your knee. For these reasons this is a very personal decision.   It is important to also consider while there is no consensus as to whether running itself causes arthritis, there is some evidence that it can influence its progression in a knee that has a history of injury. Additionally, even in normal knees there is evidence that more extreme distances may increase one’s chances of arthritis likely due to causing more joint damage that is greater than the body’s ability to repair itself.

The decision will need to be your own and you can of course ask your own physician for further guidance.   There are other options than completely quitting running such as running shorter distances and focusing on shorter multisport races.   Training more in swimming and cycling would decrease joint impact and are great options for people even with active arthritis.  Continuing a strengthening program that promotes core, hip, and VMO strength would also be recommended, these are likely exercises you did in PT.   While it may be difficult or impossible to return to your pre-injury mechanics, strength in the core muscles may protect your knee by decreasing the impact on the articular cartilage.   It’s important to note that all these recommendations have not been well studied.  Even people who already have mild symptoms of arthritis and some changes on x-ray decide to do different things with this information. Unlike you these people already have arthritis thus they know that it will be progressive. Some people decide to participate in their activities including ironman triathlons and marathons as long as possible, some decrease the amount of running and do more activities with less impact with hopes of being able to enjoy activities longer, and some choose to give up a beloved activity in hopes of not needing a replacement as early or having to go through life disabled. For you the decision is perhaps even more complex given that it sounds like you do not have signs or symptoms of arthritis but are worried about your risk of developing it.

As a side note, there are many new technologies in various stages of research including medications, and biologic treatments, minimally invasive implants that we hope will be able to decrease the burden of osteoarthritis. However, at this time the long term outcomes have not been well studied for the majority of these.   You may want to stay up to date on these new technologies but be sure to also be a critical healthcare consumer as sometimes outcomes are overstated, especially on individual companies and clinics websites.  

Stiebel M, Miller LE, Block JE. Post-traumatic knee osteoarthritis in the young patient: therapeutic dilemmas and emerging technologies. Open Access Journal of Sports Medicine. 2014;5:73-79. doi:10.2147/OAJSM.S61865.


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date: September 28, 2017


The American Medical Society for Sports Medicine (AMSSM) was formed in 1991 to fill a void that has existed in sports medicine from its earliest beginnings. The founders most recognized and expert sports medicine specialists realized that while there are several physician organizations which support sports medicine, there has not been a forum specific for primary care non-surgical sports medicine physicians.



The American Medical Society for Sports Medicine (AMSSM) was formed in 1991 to fill a void that has existed in sports medicine from its earliest beginnings. The founders most recognized and expert sports medicine specialists realized that while there are several physician organizations which support sports medicine, there has not been a forum specific for primary care non-surgical sports medicine physicians.


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