ACL Injury Diagnosis and Treatment
The anterior cruciate ligament is one of the four major stabilizing ligaments in the knee, connecting the femur to the tibia and providing the rotational stability that allows the knee to handle pivoting, cutting, and sudden changes of direction. An ACL tear is one of the most common and consequential injuries in sports medicine — and it can also occur during everyday activities like a misstep on stairs, an awkward landing from a jump, or a sudden twist of the knee. Most patients hear or feel a pop at the moment of injury, followed by rapid swelling, significant pain, and a sensation that the knee is giving way or cannot be trusted to bear weight. Because the ACL does not heal reliably on its own, an accurate diagnosis and a clear understanding of the available treatment options are essential for making the best long-term decision about your knee.
Dr. Jonathan Glashow is a board-certified orthopedic surgeon and Clinical Associate Professor of Orthopedic Surgery at NYU Grossman School of Medicine — widely recognized as one of the nation’s leading ACL specialists. His published research in the Journal of Bone and Joint Surgery includes one of the earliest double-blind studies evaluating MRI accuracy for anterior cruciate and meniscal lesions, helping establish the diagnostic standards still used in clinical practice today. With over 30 years of experience, more than 15,000 procedures performed, and roles as Chief Medical Officer for the New Jersey Devils and Philadelphia 76ers, Dr. Glashow has diagnosed and treated ACL injuries at every level — from professional athletes returning to competition to weekend warriors and teenagers sustaining their first knee injury. Named a Castle Connolly Top Doctor every year since 2000, he provides comprehensive ACL evaluation and treatment at his Upper East Side practice in New York City.
“Every ACL injury is different — the tear pattern, the patient’s anatomy, their activity level, and their goals all factor into the treatment decision,” says Dr. Glashow. “My job is to give each patient a clear, honest assessment of their options so they can make the most informed choice about their knee.”
Signs and Symptoms of an ACL Tear
An ACL tear typically produces a recognizable set of symptoms that develop immediately or within the first few hours after injury. Common signs include:
- An audible pop or snapping sensation at the time of injury
- Rapid onset of swelling — usually within the first several hours — caused by bleeding from the torn ligament
- Significant pain, particularly when attempting to bear weight
- A feeling of instability or the knee buckling or giving way
- Loss of range of motion, especially difficulty fully straightening the knee
Not every ACL injury presents with all of these symptoms, and in some cases the initial pain subsides enough that patients attempt to return to activity — only to experience repeated episodes of the knee giving way. Dr. Glashow recommends evaluation for any knee injury involving a pop, rapid swelling, or a sensation of instability, even if the pain seems manageable.
How ACL Injuries Are Diagnosed
Dr. Glashow begins with a detailed history of the injury mechanism followed by a comprehensive physical examination. Manual stability tests — including the Lachman test, anterior drawer test, and pivot shift test — assess how much the tibia moves in relation to the femur and help determine the degree of ligament damage. In the acute phase, pain and swelling can make these tests difficult to perform, and an arthrometer may be used to measure joint laxity more precisely.
X-rays are taken to rule out fractures, bone chips, or signs of associated injury. An MRI is often ordered to confirm the ACL tear, evaluate the condition of the menisci and other ligaments, and assess the overall health of the knee joint — information that is critical for surgical planning. In most cases, a definitive diagnosis can be made through examination and imaging without the need for diagnostic arthroscopy. Same-day X-rays and MRI are available at Dr. Glashow’s Upper East Side practice.
Treatment Options for ACL Injuries
The right treatment for an ACL tear depends on several factors, including the severity and location of the tear, the patient’s age and activity level, whether other structures in the knee are also damaged, and the patient’s goals for returning to sport or physical activity. Dr. Glashow discusses all available options with every patient and takes a personalized approach to treatment planning.
Immediate care for any ACL injury follows the standard RICE protocol — rest, ice, compression, and elevation — to control swelling and pain in the days following the injury. The knee may be drained of excess fluid to reduce pressure and improve comfort. From there, the treatment path diverges based on the individual case.
Non-Surgical ACL Treatment
The ACL does not heal reliably on its own, but not every ACL tear requires surgery. Patients who may do well without reconstruction include older or less active individuals, those willing to modify their activity level to avoid pivoting and cutting sports, and patients with partial tears where the knee remains functionally stable. A structured rehabilitation program focusing on strengthening the muscles around the knee — particularly the hamstrings and quadriceps — can restore enough functional stability for daily activities and low-impact exercise. Dr. Glashow monitors non-surgical patients closely, because those who continue to experience instability or re-injury are at increased risk for meniscal tears and accelerated cartilage damage that can lead to early arthritis.
Surgical Treatment for ACL Tears
Surgery is generally recommended for active individuals who want to return to sports involving pivoting, cutting, or sudden direction changes, for patients who continue to experience instability despite rehabilitation, and for those with multi-ligament injuries. The two primary surgical approaches Dr. Glashow offers are ACL reconstruction — in which the torn ligament is replaced with a tendon graft — and, for select patients with acute tears, ACL repair with BEAR implant or internal brace augmentation. Each approach has specific advantages depending on the tear pattern and the patient’s goals, and Dr. Glashow determines the best option after a thorough evaluation. For detailed information on the reconstruction procedure, visit the ACL Reconstruction page.
Recovery After ACL Surgery
Recovery from ACL surgery follows a structured, phased rehabilitation protocol that Dr. Glashow coordinates closely with physical therapists, athletic trainers, and coaches. The general timeline includes:
Phase one focuses on reducing swelling and restoring range of motion. Crutches are typically used for the first seven to ten days. Stationary bike riding without resistance and pool exercises usually begin about seven to ten days after surgery. Driving is often possible within two weeks.
Phase two introduces progressive strengthening, beginning around six weeks after surgery. Resistance tools, treadmill walking, and the elliptical trainer are added gradually, with weight-based strengthening typically starting around two to three weeks.
Phase three adds sport-specific exercises. Running is usually permitted between four and eight weeks, with pivoting and cutting drills beginning at four to five months. This phase is customized to the patient’s sport and competitive level.
The final phase involves a supervised return to sport, which typically occurs approximately six to nine months after reconstructive surgery. Dr. Glashow evaluates each patient’s knee stability, strength, range of motion, and sport-specific readiness before clearing them for full competition.
Lamarr Houston (Chicago Bears), a patient of Dr. Glashow, 4 months post ACL surgery:
Schedule an ACL Evaluation in New York City
If you have sustained a knee injury involving a pop, rapid swelling, or a sensation of instability — or if you have been diagnosed with an ACL tear and want a second opinion before deciding on treatment — Dr. Glashow provides same-day evaluation with on-site MRI and X-ray at his Upper East Side practice. With over three decades of experience treating ACL injuries at every level of sport and the full range of treatment options available — from conservative rehabilitation to advanced reconstruction and repair techniques — his practice offers the kind of expert, individualized care that gives patients the best chance at a full, lasting recovery. Contact our office to schedule your consultation — we accept out-of-network insurance benefits and offer same-day, after-hours, weekend, and emergency appointments.
Frequently Asked Questions About ACL Injuries
Can the ACL heal by itself?
Some partially torn ACLs — particularly in children and adolescents — may heal without surgery if the knee remains stable. However, a complete ACL tear rarely heals on its own because the ligament sits within the joint, has a limited blood supply, and the torn ends retract and cannot reconnect. Even when the torn ends scar to adjacent structures, this rarely restores meaningful stability. For complete tears, ACL reconstruction — replacing the ligament with a graft — remains the standard of care for patients who want to return to full activity.
Is surgery always necessary for an ACL tear?
No. Partial tears with a stable knee can often be managed with bracing and a structured rehabilitation program. Some patients with complete tears — typically older, less active individuals who are willing to avoid pivoting sports — can function well without reconstruction. However, patients who continue to experience knee instability after rehabilitation are at significantly higher risk for meniscal tears and cartilage damage that can lead to early-onset arthritis. Dr. Glashow evaluates each patient individually and recommends surgery only when the clinical picture supports it.
How is an ACL tear diagnosed?
Dr. Glashow uses a combination of clinical examination — including the Lachman test, anterior drawer test, and pivot shift test — along with X-rays and MRI. The physical exam assesses the degree of knee instability, while the MRI confirms the tear, reveals associated injuries to the menisci and other ligaments, and provides the detailed information needed for surgical planning. Same-day imaging is available at his Upper East Side practice.
Which graft is best for ACL reconstruction?
There is no single graft that is universally best — the choice depends on the patient’s age, activity level, anatomy, and the surgeon’s experience with the technique. Common options include hamstring tendon autograft, patellar tendon autograft, and quadriceps tendon autograft. Each has specific advantages and trade-offs related to graft strength, donor site discomfort, and rehabilitation. Dr. Glashow discusses the pros and cons of each option during the consultation and recommends the graft that best matches the individual patient’s needs.
When can I return to sports after ACL surgery?
Most patients begin a return-to-sport progression approximately six months after reconstruction, with full clearance for unrestricted competition typically occurring between nine and twelve months — depending on the sport, the graft type, and the patient’s individual healing and rehabilitation progress. Dr. Glashow uses objective criteria including strength testing, stability assessment, and sport-specific functional testing to determine readiness rather than relying on a calendar timeline alone.
Are knee braces used after ACL reconstruction?
A post-operative brace is typically used immediately after surgery to limit motion and protect the graft during the early healing phase. As rehabilitation progresses, a lighter functional brace may be used during activity to provide additional support while the graft matures. Dr. Glashow makes bracing recommendations based on the specific graft type, the surgical technique, and the patient’s activity demands.
