Kansas City Chiefs quarterback Patrick Mahomes has placed renewed attention on one of the most serious injuries in sports medicine: a torn anterior cruciate ligament (ACL). According to People, Mahomes returned to throwing drills while wearing a heavy-duty knee brace during rehabilitation in late May, marking an important milestone in his recovery process. Because the ACL is so vital for stability and explosive movement, his rehabilitation journey has naturally captured the attention of sports fans everywhere.
While modern surgical techniques have significantly improved outcomes, recovery remains lengthy and demanding. For elite athletes like Mahomes, rehabilitation involves carefully restoring strength, balance, flexibility and confidence in the injured knee before returning to competition. Understanding what an ACL tear is, how it occurs and how it is treated can help athletes and non-athletes alike recognize the seriousness of the injury and the importance of proper medical care.
What’s happening in your body
The anterior cruciate ligament is one of the four major ligaments that stabilize the knee joint. It connects the femur (thigh bone) to the tibia (shin bone) and helps prevent excessive forward movement and rotational instability of the knee.
When the ACL tears, the ligament fibers partially or completely rupture. As a result, the knee loses an important source of stability. Many people report hearing or feeling a distinct “pop” at the moment of injury, followed by immediate pain, swelling and difficulty bearing weight. Orthopedic specialists note that swelling often develops quickly because blood vessels within the ligament are damaged during the tear.
Common causes
ACL tears frequently occur during sports that require rapid acceleration, deceleration, pivoting and jumping. Football, basketball, soccer, skiing and tennis are among the activities most commonly associated with these injuries.
Common causes include:
- Sudden changes in direction
- Awkward landings after jumping
- Rapid deceleration while running
- Direct contact to the knee
- Hyperextension injuries
- Pivoting on a planted foot
The National Library of Medicine suggests that approximately 70% of ACL tears occur without direct contact from another player. Instead, the injury often happens when an athlete plants a foot and attempts to change direction too quickly.
Although ACL tears can happen to anyone, certain biomechanical and environmental factors significantly increase risk. Athletes who repeatedly perform cutting maneuvers place enormous rotational stress on the knee joint. When the force exceeds the ligament’s strength, the ACL can rupture.
Muscle imbalances also play a role. Weak hamstrings, underdeveloped gluteal muscles and poor neuromuscular control can increase strain on the ligament. Fatigue may further impair coordination, increasing the likelihood of awkward movements.
Playing surfaces, footwear and year-round sports participation have also received attention from sports medicine experts. According to orthopedic specialists at Loma Linda University Health, increasing sports specialization and greater athletic participation may be contributing to the rise in ACL injuries. In football specifically, quarterbacks may sustain ACL tears while scrambling, planting to throw or absorbing awkward contact from defenders.
Diagnosis
Diagnosing an ACL tear begins with a detailed medical history and physical examination. Physicians evaluate knee stability using specialized tests such as the Lachman test, anterior drawer test and pivot-shift test.
Magnetic resonance imaging (MRI) is considered the gold standard because it allows physicians to visualize ligament damage and identify associated injuries involving cartilage, bone or the meniscus. Orthopedic experts emphasize that MRI findings must be interpreted alongside the patient’s symptoms and physical examination.
“Imaging studies play a critical role,” Dr. Diana Rangaves, PharmD, tells Blavity Health. “MRI uses a very strong magnetic field and radio waves to make the water molecules in your body give off signals. The computer reads these signals and turns them into a black-and-white picture of your inside tissues. Healthy tissues give off a predictable, uniform signal. A signal alteration means that a specific spot in your body is sending a signal that differs from the healthy tissue surrounding it.”
ACL tear treatment
Treatment depends on several factors:
- Age
- Activity level
- Degree of instability
- Presence of associated injuries
- Athletic goals
Some individuals can manage with physical therapy alone, particularly if they do not participate in high-demand sports. However, younger, highly active patients often undergo ACL reconstruction to restore knee stability and reduce the risk of long-term joint damage.
For professional athletes such as Mahomes, diagnosis and treatment involve an extensive multidisciplinary approach. “Patrick Mahomes successfully underwent surgery in Dallas this evening with Dr. Dan Cooper to repair the tear in his left ACL,” the Chiefs announced in a December 2025 statement, per the NFL. “Mahomes will begin his rehab process immediately.”
Following injury, physicians typically perform immediate imaging to confirm the diagnosis and determine whether additional structures have been damaged. Once swelling is controlled, athletes often begin “prehabilitation” before surgery. This phase focuses on restoring range of motion, reducing inflammation and strengthening surrounding muscles. Research shows that entering surgery with better knee function can improve postoperative outcomes.
ACL reconstruction surgery usually involves replacing the torn ligament with a graft. Surgeons may use tissue harvested from the patient’s own body – commonly the patellar tendon, hamstring tendon or quadriceps tendon – or donor tissue.
How long will it take Mahomes to recover from his torn ACL?
While medical experts generally estimate a nine-to-twelve-month timeline for athletes to safely return to full competition after ACL reconstruction, Patrick Mahomes is already making impressive strides. He is currently following a highly structured rehabilitation process and has recently advanced to throwing drills while wearing a protective brace.
ESPN reports that Mahomes shared his excitement directly with fans, documenting his progress on social media with an enthusiastic, “Day by day! Great being able to throw the ball around today!”
Chiefs head coach Andy Reid is emphasizing a patient approach rather than rushing his star quarterback back onto the field, noting that the organization plans to evaluate his recovery on a strictly day-by-day basis. Reid has praised Mahomes’ dedication to his extensive rehabilitation, expressing absolute confidence in his mindset. Grounding the team’s outlook in optimism in an interview, Reid shared, “He’ll attack it, just like he does everything else,” adding, “He’ll get after it, and he’s got good people here to rehab him. He’ll be right on top of all of that.”
Why are ACL tears so common now?
Sports medicine specialists at the Shelbourne Knee Center believe multiple factors are contributing to the growing number of ACL injuries. Orthopedic experts say increased participation in organized athletics and a stronger emphasis on year-round competition have contributed to rising injury rates. Young athletes often specialize in a single sport at younger ages, leading to repetitive stress on the same joints and movement patterns.
Modern athletes are also bigger, stronger and faster than previous generations. While muscles continue to develop through advanced training methods, ligaments do not necessarily strengthen at the same rate. This can create situations where tremendous forces are transmitted through relatively unchanged connective tissues.
When to see a doctor
Anyone who experiences a popping sensation in the knee followed by swelling, pain, instability or difficulty walking should seek medical evaluation promptly. Immediate assessment is especially important if the knee gives way during activity or becomes significantly swollen within a few hours. Early diagnosis can help prevent further damage to the meniscus, cartilage and surrounding structures.
Bottom line
Patrick Mahomes’ ACL tear highlights both the seriousness of ACL injuries and the advances that have transformed recovery prospects for athletes. While ACL tears often require surgery and months of rehabilitation, many patients successfully return to their previous levels of activity. Mahomes’ progress in returning to practice activities represents an encouraging sign, but a full return to elite competition depends on completing every stage of recovery safely.
Frequently Asked Questions
What sport has the highest ACL tear rate?
According to the Shelbourne Knee Center, soccer players are most likely to suffer ACL injuries due to the unpredictable foot planting and rotational movements involved in the sport.
How painful is ACL surgery?
ACL surgery is performed under anesthesia, so patients do not feel pain during the procedure itself.
Citations
People. Patrick Mahomes Seen Practicing in a Leg Brace for the First Time Since His Season-Ending Injury. People. https://people.com/patrick-mahomes-seen-practicing-leg-brace-first-time-since-season-ending-injury-11934480
Brophy RH, Wojtys EM, Mack CD, Hawaldar K, Herzog MM, Owens BD. Factors Associated With the Mechanism of ACL Tears in the National Football League: A Video-Based Analysis. Orthopaedic Journal of Sports Medicine. 2021;9(11). doi:https://doi.org/10.1177/23259671211053301.
Loma Linda University Health. ACL Injuries Are on the Rise, but Can They Be Prevented?. Loma Linda University Health. https://news.llu.edu/health-wellness/acl-injuries-are-rise-can-they-be-prevented
Gordon G. Chiefs QB Patrick Mahomes undergoes successful surgery to repair ACL, LCL. NFL.com. Published December 15, 2025. https://www.nfl.com/news/chiefs-qb-patrick-mahomes-undergoes-successful-surgery-to-repair-acl-lcl
Jahic, D., Omerovic, D., Tanovic, A., Dzankovic, F., & Campara, M. (2018). The Effect of Prehabilitation on Postoperative Outcome in Patients Following Primary Total Knee Arthroplasty. Medical Archives, 72, 439. https://doi.org/10.5455/medarh.2018.72.439-443
ESPN. Andy Reid on Patrick Mahomes’ Week 1 Return: “Never Bet Against Him”. ESPN. Published March 31, 2026. Accessed June 5, 2026. https://www.espn.com/nfl/story/_/id/48358973/andy-reid-patrick-mahomes-week-1-return-never-bet-him
Shelbourne Knee Center. Which Athletes Have the Highest Risk of ACL Tears?. Shelbourne Knee Center. https://chnwebapp-auc-prod01.azurewebsites.net/athletes-risk-acl-tears