ACL Injuries: Causes, Symptoms, and Treatment
Medically reviewed by Sumiran Racherla, MD, Internal Medicine. Last reviewed: October 23, 2026.
What kind of doctor treats ACL Injuries?
An orthopedic surgeon (a bone and joint doctor) treats ACL injuries, along with a physical therapist (a movement and exercise expert). Many people first see a primary care doctor after a knee injury. An MRI scan (a detailed picture of the knee) shows the tear. A direct primary care or concierge doctor can be a first stop for an evaluation and can refer you to a specialist when needed.
What are ACL injuries?
ACL injuries are tears or stretches of the anterior cruciate ligament (ACL). The ACL is a ligament, a tough band of tissue, inside the knee. It runs diagonally in the middle of the knee. It keeps the shinbone from sliding out in front of the thighbone. It also gives the knee rotational stability, which means steadiness when turning. The knee has four main ligaments. They act like strong ropes to hold the bones together. A tear can be partial or complete. Most ACL tears do not heal on their own. ACL injuries often happen along with other knee injuries, such as a torn meniscus (the knee's shock absorber).
Symptoms
When the ACL tears, you might hear a popping noise, and the knee may give way. Other common signs are:
- Pain and swelling. The knee swells within 6 hours of the injury.
- Pain when you try to put weight on the leg.
- Loss of full range of motion.
- Tenderness along the joint line.
- A feeling that the knee is unstable or gives out.
The swelling and pain may go away on their own. But using the knee too soon can worsen instability and risk more damage to the knee.
Causes and who gets it
The ACL can tear when you change direction fast, stop suddenly, slow down while running, land from a jump wrong, or take a direct hit such as a football tackle. These moves are common in volleyball, soccer, football, basketball, and skiing. Most ACL injuries happen without a direct hit to the knee. Anyone can tear an ACL. Female athletes get ACL injuries at rates 2 to 8 times higher than males. This may come from differences in knee shape, movement, and hormones. Other risk factors include a higher body mass index (BMI, a weight-to-height measure), looser joints, younger age, and weaker lower leg muscles.
How doctors diagnose it
The doctor asks how the injury happened. Then the doctor checks the injured knee and compares it with the other knee. X-rays do not show ligaments, but they can find bone injuries. An MRI (magnetic resonance imaging) scan gives the best view of ligaments and cartilage. It can confirm the tear and show other knee injuries. Doctors also grade the sprain from 1 to 3. A grade 3 sprain is a complete tear, and the knee joint is unstable.
Treatment
Treatment depends on your age, activity level, how unstable the knee feels, and your goals. Non-surgical care is always an option. It includes ice, pain relievers, a brace, and physical therapy to rebuild strength. Some people live and function normally with a torn ACL. But most people feel that the knee is unstable, and an unstable knee can lead to more damage. Complete tears usually need surgery to rebuild the ligament. This is called reconstruction. The surgeon uses a tendon graft (replacement tissue) from your own body, such as the patellar or hamstring tendon, or from a tissue donor. Active people who do pivoting sports or heavy work are encouraged to consider surgery. Physical therapy is a crucial (very important) part of recovery, with exercises starting soon after surgery.
When to see a doctor
See your doctor right away after a serious knee injury. Do not play sports until you have been treated. Call 911 or go to the emergency room if the foot is cool and blue after a knee injury. This can mean the knee joint is dislocated and blood vessels to the foot are injured. This is a medical emergency.
How a direct primary care or concierge doctor fits in
A direct primary care doctor charges a flat monthly fee instead of billing insurance, while a concierge doctor usually charges more and often works alongside insurance. A direct primary care doctor can examine the knee, order first tests like X-rays, and refer you to an orthopedic surgeon. The doctor can also follow recovery and coordinate physical therapy.
Common questions
Can an ACL tear heal without surgery?
Most ACL tears do not heal on their own. Partial tears may do well with physical therapy alone. Complete tears usually need surgery, especially for active people. Some people choose not to have surgery, but many then feel that the knee is unstable.
How long is recovery after ACL surgery?
Most people return to full sports within 6 to 12 months after surgery. This happens once pain and swelling are gone and strength, motion, and balance are fully restored. Physical therapy is a key part of that recovery.
Are women more likely to tear an ACL?
Yes. Female athletes get ACL injuries at rates 2 to 8 times higher than males. Differences in knee shape, movement, and hormones may play a role. Anyone who plays cutting or pivoting sports can tear an ACL.
Sources
- AAOS OrthoInfo - Anterior Cruciate Ligament (ACL) Injuries
- MedlinePlus - Anterior cruciate ligament (ACL) injury
- AAOS OrthoInfo - ACL Injury: Does It Require Surgery?
Medical Disclaimer
This content is for general educational and informational purposes only and is not medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment, and reading it does not create a doctor-patient relationship. Always seek the advice of your physician or another qualified health provider with any questions about a medical condition, and never disregard or delay seeking professional advice because of something you read here. If you think you may have a medical emergency, call 911 (or your local emergency number) immediately.
