When Does a Partial ACL Tear Require Surgery?

The anterior cruciate ligament (or ACL) is one of the primary ligaments, or connective tissues, in the knee joint. An ACL tear can be either partial or complete. Complete tears usually require surgery, but some partial tears are treatable with non-surgical techniques. If you have a partial tear, your healthcare provider may assess the need for surgery based on how unstable your knee is. If your knee is stable, you may not need surgery.

The decision to have surgery can be a difficult one since ACL reconstruction involves significant rehabilitation and other operative risks.

This article discusses partial ACL tears and how your healthcare provider may help you decide if you need ACL surgery.

Photo of a woman therapist examining a man's knee.
Kali9 / Getty Images

What Is a Partial ACL Tear?

The ACL is important because it allows for normal movement and mechanics of the knee joint. It connects your thigh bone (femur) to your shinbone (tibia) and keeps your tibia from sliding too far forward. It also performs other functions to maintain the stability of your knee when you rotate it. When it is injured, it is called a sprain.

ACL injuries most commonly occur when landing a jump, making a sudden change in running direction or falling. When the ACL is torn, you may notice problems in the way your knee functions. Some common symptoms of an injured ACL include:

  • Pain and swelling around the knee joint
  • Loss of full range of motion
  • Tenderness along the joint line
  • Discomfort when walking

A partial ACL tear is also called a grade 2 sprain. Grade 2 injuries are rare and occur when the ligament stretches enough to become loose and damaged.

It is not always clear if partial tears should be treated surgically since in many cases it is possible to recover after nonsurgical rehabilitation. The decision often depends on your pain level and whether or not your knee is unstable.

By contrast, a grade 1 sprain is when the ligament is slightly stretched and damaged but the knee is still fairly stable. A grade 3 sprain is a complete tear of the ACL. With this injury, the knee joint becomes unstable and surgery is almost always necessary to correct it.

When Surgery Is Considered

Your healthcare provider will consider a few different factors when deciding if your partial ACL tear requires surgery.

  • Physical exam: A physical exam can help assess the extent of your injury. This will often include a Lachman test, which places stress on the ACL, and a pivot-shift test, which is a subjective test of the knee.
  • Knee instability: Treatment of a partial ACL tear is most dependent on how much knee instability is caused by the injury. Your healthcare provider will assess this during an exam, or you may experience it independently. If you have multiple episodes of your knee giving way while walking, for example, surgery may be recommended.
  • Age: Research shows that ACL surgery in people over the age of 50 is just as successful as it is in younger people. Older people, however, may have longer recovery times. They also tend to have more complications after surgery. For this reason, people in the 50+ age group may want to consider non-surgical treatment, especially if they are not active. 
  • Pain level: Surgery may be a good option if you are experiencing a lot of pain and if ongoing pain is likely to impact your quality of life.
  • Athleticism: If you are an athlete or work in a profession that requires you to be on your feet, surgery will give you the best chance of being able to return to these activities.
  • Other knee injuries: If you have a torn meniscus, broken bones, or injuries to other ligaments or tendons, surgery may be necessary to restore the function of the knee. 
  • If growth plates are still open: Children with partial ACL tears need special evaluation, since growth plates don't close until between the ages of 14 and 16. Growth plates are structures that allow the bones to become longer as a child grows. New surgical techniques may help repair ACL injuries in children who are not likely to benefit from non-surgical treatment, such as athletes.

If the need for surgery isn't clear, you may receive an arthroscopy. During this procedure, a surgeon threads a tube with a camera through a small incision so that they can visualize and diagnose problems inside a joint.

For an ACL injury, however, arthroscopy can be very subjective. Healthcare providers may have differing opinions on the scope of the problem and the "right" remedy.

Partial ACL Reconstruction

While grade 3 injuries often require complete reconstruction, a grade 2 injury may be treated with partial reconstruction. During this procedure, the ACL is reconstructed using tissue obtained either from somewhere else in the body or from a donor. The new ligament is created to replace the damaged ligament.

This surgery can be a good option for people with partial ACL tears. Studies have shown that most patients undergoing partial reconstruction will have improved knee stability and function.

After this procedure, you will likely have to wear a knee brace for a few weeks. Physical therapy may be needed for several months to help restore function to your knee. Research suggests that many people who have had this type of surgery can return to sports and similar activities after about six months.

Non-Surgical Treatment

Most patients with partial tears can recover without surgery. Recovery time typically takes about three months.

When surgery isn't recommended, several non-surgical treatments can help people with partial ACL tears. These treatments often include bracing and the use of crutches to help protect the knee during recovery. Physical rehabilitation therapy can begin once the swelling goes down.

The goal of nonsurgical treatment is to maintain the strength of the muscles surrounding the joint and to try to optimize the stability of the joint. A custom sports brace may be fitted for patients who want to return to athletic activity.

Surgery Isn't For Everyone

Nonsurgical treatment can be a good choice for older patients or those who have a low activity level.


The most common treatment for an injured anterior cruciate ligament in a young, active person is surgical reconstruction of the ligament. The decision to proceed with the surgery is best made by determining the amount of knee instability.

Trying to determine the extent of the injury can be difficult. If a partial ACL tear is suspected, an orthopedic surgeon can help assess the degree of instability and whether ACL reconstruction might be a reasonable treatment.

A Word From Verywell

Whether or not surgery lies in your future, physical therapy almost certainly will. It's the surest way to help you regain strength and motion in your knee.

Therapy programs are often divided into three phases. Phase one focuses on returning motion to the joint and surrounding muscles. Phase two centers on a strengthening regimen designed to protect the ligament. Phase three pivots on ensuring that the knee is strong enough to sustain a return to normal, functional activities.

Complete recovery can take many months, so make sure to work closely with your physical therapist and follow up with your healthcare provider as needed.

Frequently Asked Questions

  • Will I need X-rays to see if I have an ACL tear?

    Probably not. An X-ray will reveal the presence of a broken bone, but not a torn ligament. A thorough physical exam, along with a review of your medical history, is usually enough to make an ACL diagnosis.

  • Will I be able to return to playing basketball after ACL surgery?

    All things depend on how well you follow the advice of your healthcare team, including your physical therapist. But it's fair to expect that it will take at least six months before you can resume play.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Filbay SR, Grindem H. Evidence-based recommendations for the management of anterior cruciate ligament (ACL) ruptureBest Pract Res Clin Rheumatol. 2019;33(1):33-47. doi:10.1016/j.berh.2019.01.018.

  2. Panisset JC, Gonzalez JF, de Lavigne C, et al. ACL reconstruction in over-50 year-olds: comparative study between prospective series of over-50 year-old and under-40 year-old patients. Orthop Traumatol Surg Res. 2019;105(8):S259-65. doi:10.1016/j.otsr.2019.09.009

  3. Salesky MA, Oeding JF, Zhang AL, Ma CB, Feeley BT, Lansdown DA. Patients aged 50 years and older have greater complication rates after anterior cruciate ligament reconstruction: a large database study. Arthrosc Sports Med Rehabil. 2021;3(6):e1827-34. doi:10.1016/j.asmr.2021.08.010

  4. Johns Hopkins Medicine. Sparing the growth plate in ACL reconstruction.

  5. Sonnery-Cottet B, Panisset JC, Colombet P, et al. Partial ACL reconstruction with preservation of the posterolateral bundle. Orthop Traumatol Surg Res. 2012;98(8):S165-70. doi:10.1016/j.otsr.2012.10.001

  6. Carulli C, Innocenti M, Roselli G, et al. Partial rupture of anterior cruciate ligament: preliminary experience of selective reconstructionJ Orthop Traumatol. 2020;21(1):1-9 doi:10.1186/s10195-020-0544-0

  7. American Academy of Orthopedic Surgeons. ACL injury: does it require surgery?

  8. American Academy of Orthopaedic Surgeons. Anterior cruciate ligament (ACL) injuries.

By Jonathan Cluett, MD
Jonathan Cluett, MD, is board-certified in orthopedic surgery. He served as assistant team physician to Chivas USA (Major League Soccer) and the United States men's and women's national soccer teams.