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Conor McGregor’s UFC 329 comeback ended in 69 seconds when his right knee buckled after a jumping switch kick. MMA knee injuries like his have become one of the most common reasons fighters land in an orthopaedic clinic. After more than twenty years treating knees at the Bone and Joint Institute of Tennessee, I can tell you these injuries follow patterns that are actually predictable once you understand the joint under pressure.
Here is what patients (and any concerned MMA fan) should know about the four most common MMA knee injuries, why they keep happening at the elite level, and what real recovery looks like.
What are the most common MMA knee injuries?
The four most common MMA knee injuries are ACL tears, MCL sprains, meniscus tears, and patella dislocations. These four account for the majority of knee complaints in fighters, and each has a different mechanism, a different recovery timeline, and a different long-term outlook.
ACL tears
An anterior cruciate ligament (ACL) tear is the injury McGregor’s team suspects he suffered at UFC 329. The ACL is a rope-like ligament deep inside the knee that stops the shin bone from sliding forward on the thigh bone.
In fighters, the classic ACL tear happens on a planted foot: the athlete lands from a jumping kick, changes direction, or gets caught in a scramble while the foot stays fixed and the knee rotates. Patients often describe a loud pop, immediate swelling, and a knee that feels unstable when they try to stand.
In my practice, I see the same knee mechanics show up in weekend warriors: a pivot on a fixed foot, a sudden shift, and the ligament simply cannot hold.
MCL sprains
The medial collateral ligament (MCL) runs along the inner side of the knee. It is the most commonly sprained ligament in combat sports because grappling, takedowns, and guard passing all push the knee inward while the foot is planted. A Brazilian jiu-jitsu study cited in Sports Health found that joint injuries made up 64.5 percent of competition injuries, with the knee and elbow leading the list.
The good news: the MCL has a rich blood supply. Most Grade 1 and Grade 2 MCL sprains heal without surgery, with bracing, physiotherapy, and a gradual return to sport.
Meniscus tears
The meniscus is a crescent-shaped shock absorber between the thigh bone and the shin bone. There are two in each knee. A meniscus tear happens when the joint twists under load, which is exactly what a fighter’s knee does during a scramble, a takedown, or an awkward landing.
Small tears in the outer edge of the meniscus can sometimes heal on their own, because that zone has blood supply. Tears in the inner two-thirds often need an arthroscopic procedure, either a small trim (meniscectomy) or a repair with sutures.
Patella dislocations
The patella (kneecap) rides in a groove on the front of the thigh bone. A direct blow to the side of the knee, or a sudden inward pivot on a planted foot, can pop the kneecap out of that groove. Kickboxing, taekwondo, and judo see this injury regularly.
A first-time dislocation often responds to reduction, bracing, and physiotherapy. Recurrent dislocations, or ones with cartilage damage, may need surgery to reconstruct the medial patellofemoral ligament.
What happened to Conor McGregor’s knee at UFC 329?
Conor McGregor injured his right knee 69 seconds into his UFC 329 return against Max Holloway on 11 July 2026 in Las Vegas. He threw a jumping switch kick to open the fight, landed awkwardly on the right leg, and the knee buckled inward. He tried to continue with two more kicks and could not put weight on the leg. The referee stopped the bout.
UFC CEO Dana White told reporters after the fight that his team was assuming a blown ACL, adding that the ringside doctors agreed. A UFC reporter said McGregor was diagnosed with a right internal knee injury at the arena. A confirmed diagnosis waits on MRI.
McGregor has denied any pre-existing injury and said the damage came out of nowhere. His head coach John Kavanagh backed him up, calling the opening switch kick a move drilled daily in camp.
McGregor is 37 and was fighting for the first time in five years. His only prior ACL tear, in 2013, was in the left knee and healed in about 11 months after surgery.
Why do MMA knee injuries happen so often?
MMA loads the knee in almost every position the joint is designed to fail in. Striking-predominant styles like Muay Thai and karate produce high rates of foot, ankle, and knee injuries because the athlete’s planted leg absorbs both the rotational torque of the kick and the impact of the landing.
Submission-predominant styles like Brazilian jiu-jitsu, judo, and wrestling put the knee in twisted, pinned positions during guard passing, takedowns, and heel-hook defence.
Three biomechanical patterns show up over and over in the fighters and weekend athletes I see:
- A planted foot with a rotating body. This is McGregor’s UFC 329 mechanism, and it is the classic ACL setup.
- An inward force on a fixed foot. This is the MCL setup, common in takedown defence.
- A twisting motion under compression. This is the meniscus setup, common in scrambles and awkward landings.
Elite fighters train these movements thousands of times. Even great technique cannot always protect a ligament from a bad angle at bad speed.
How are MMA knee injuries treated?
Treatment depends on which structure is torn, how bad the tear is, and whether the patient wants to return to a high-impact sport. Most treatment plans fall into three tiers.
Conservative care handles most Grade 1 and Grade 2 MCL sprains and many small meniscus tears. Rest, ice, compression, elevation, and structured physiotherapy carry the athlete back to activity in weeks to a few months.
Arthroscopic surgery is a minimally invasive keyhole procedure used for many meniscus tears and for some patella and cartilage injuries. Recovery is measured in weeks, not months, and most patients walk out the same day.
ACL reconstruction is the big one. When a competitive athlete tears the ACL, the ligament cannot heal on its own, and surgical reconstruction is usually needed to restore stability. Surgeons rebuild the ligament using a graft from the patient’s hamstring, patellar tendon, or a donor.
At the Bone and Joint Institute of Tennessee, our sports medicine colleagues handle ACL reconstructions and complex sports knee cases. My own practice focuses on adult hip and knee replacement for patients whose joint arthritis has progressed beyond conservative care.
What does recovery from a torn ACL look like?
Recovery from a full ACL reconstruction typically takes 9 to 12 months before a competitive athlete returns to full sport. The first six weeks focus on protecting the graft, regaining range of motion, and reducing swelling. Months three to six build quadriceps and hamstring strength. Months six to twelve rebuild sport-specific movement, agility, and confidence.
McGregor’s 2013 ACL surgery returned him to the octagon in about 11 months, which is on the fast end of that range. He was 25 then. He is 37 now, in the opposite knee, and repeat surgeries always add complexity.
Here is what I tell my patients: an ACL reconstruction is a serious operation, but it is one of the most refined procedures in orthopaedic surgery. Modern grafts, arthroscopic technique, and evidence-based rehab give most active adults an excellent shot at returning to the activities they love.
When should Franklin and Nashville patients see a specialist?
Any knee injury with a loud pop, immediate swelling, or a sense that the joint is unstable deserves an evaluation. A knee that gives way when you plant and turn, or that will not straighten or bend fully, is telling you something is wrong.
For patients across Franklin, Nashville, Brentwood, Columbia, and the wider Middle Tennessee area, the Bone and Joint Institute of Tennessee at 3000 Edward Curd Lane offers same-week evaluation for acute knee injuries. Our sports medicine team handles ligament and cartilage injuries in athletes. My practice handles the hip and knee arthritis cases that often show up years later, sometimes as a downstream consequence of a knee injury from a fighter’s twenties or thirties.
You do not need to be a UFC fighter for a knee injury to change your life. The sooner a torn ACL, MCL, or meniscus is properly evaluated, the better the long-term outlook for the joint.
If knee pain, instability, or arthritis is limiting your activity, our team is ready to help. Request a consultation with Dr. Calendine or call (615) 791-2630.
Medical disclaimer: This article is for general educational purposes and is not a substitute for personalised medical advice from a licensed orthopaedic physician. Individual outcomes vary based on the specific injury, imaging findings, age, prior surgeries, and overall health. Always consult a qualified orthopaedic surgeon or sports medicine specialist for diagnosis and treatment of any knee injury.
References
- Jensen AR, Maciel RC, Petrigliano FA, Rodriguez JP, Brooks AG. Injuries Sustained by the Mixed Martial Arts Athlete. Sports Health. 2017;9(1):64-69. doi:10.1177/1941738116664860
- Kreiswirth EM, Myer GD, Rauh MJ. Incidence of injury among male Brazilian jiu-jitsu fighters at the World Jiu-Jitsu No-Gi Championship 2009. Journal of Athletic Training. 2014;49(1):89-94.
- Scoggin JF, Brusovanik G, Izuka BH, Zandee van Rilland E, Geling O, Tokumura S. Assessment of injuries during Brazilian jiu-jitsu competition. Orthopaedic Journal of Sports Medicine. 2014;2(2):2325967114522184.
- Lystad RP, Gregory K, Wilson J. The epidemiology of injuries in mixed martial arts: a systematic review and meta-analysis. Orthopaedic Journal of Sports Medicine. 2014;2(1):2325967113518492.
- Pocecco E, Ruedl G, Stankovic N, et al. Injuries in judo: a systematic literature review including suggestions for prevention. British Journal of Sports Medicine. 2013;47(18):1139-1143.
- American Academy of Orthopaedic Surgeons (AAOS). Anterior Cruciate Ligament (ACL) Injuries. OrthoInfo. Reviewed 2024. Available at: https://orthoinfo.aaos.org/en/diseases–conditions/acl-injuries/
News sources: Conor McGregor UFC 329 injury
- The Guardian. “Conor McGregor’s UFC return ends after 69 seconds with knee injury: ‘I am beyond dark here’.” 12 July 2026. Available at: theguardian.com
- MMA Fighting. Martin D. “Conor McGregor breaks silence after devastating UFC 329 injury derails comeback: ‘I can only describe it as hell’.” 12 July 2026. Available at: mmafighting.com
- ESPN. Okamoto B. “McGregor’s coach says knee ‘never an issue’ ahead of UFC 329.” 12 July 2026. Available at: espn.com
- USA Today. Peter J. “What happened to Conor McGregor? Injury updates after UFC 329 loss to Max Holloway.” 12 July 2026. Available at: usatoday.com
