Groin Injury

Anatomy of groin injury

Groin injuries (adductor injuries) are prevalent in football, accounting for 39% of hip injuries.1 Five main muscles make up the groin: the adductor longus, adductor brevis, adductor Magnus, pectineus, and gracilis. Each of these muscles attaches from the pelvis to the femur (thigh bone), and collectively they are referred to as the “adductors” as, mechanically, they all adduct the hip (move the thigh bone towards the midline). This action of adduction is involved with running, cutting, jumping, and stabilizing on one le,g making the health of these muscles impactful for performance. 

An injury to a muscle or tendon is called a strain, whereas an injury to a ligament is referred to as a sprain. A strain is when a portion of the muscle fiber or tendon fibers becomes torn, causing swelling, pain, and, depending on severity, possible loss of strength and range of motion.2 Adductor strains occur most frequently in the adductor longus and gracilis muscles, and most commonly occur where the muscle blends into the tendon at the attachment towards the pelvis 2,3. Newer MRI studies have shown that over 60% of adductor-related groin pain in athletes involves the proximal adductor longus–enthesis complex, which is particularly vulnerable due to its long tendon and high eccentric demands in cutting and sprinting.⁷ Like all other soft tissue injuries, there is a grading system to classify severity.² With adductor strains, complete avulsions (tendon pops off the bone) are rare but can occasionally occur.³

• Grade I: Pain, minimal to no tissue injury,y minimal or no strength and range of motion loss.
• Grade II: More pain, tissue damage resulting in loss of muscle strength and range of motion, and function.
• Grade III: Complete tear of muscle or tendon resulting in complete loss of strength and function.

Cause of a groin Injury

A strain occurs when one or more of the muscles is stressed by force beyond what it is capable of controlling, causing it to either overstretch or over contract, leading to a strain of either the muscle fibers or tendon.³ Adductor strains most frequently occur via non-contact when sprinting or cutting and commonly occur when a player tries to plant his foot to cut, but his foot slides, causing a significant stretch of the groin muscle.^2,3 An example of this was David Montgomery’s injury in the 2020 preseason.

Studies in elite athletes show that adductor injuries are predominantly non-contact, with percentages ranging from 67.5%-82.5% non-contact and roughly 14% occurring due to contact.¹,⁴

There is some data on collegiate football players in positions that sustain hip injuries most frequently (not specific to adductor strains). One study shows that of all hip injuries:

• 5.8% occur in quarterbacks
• 10.3% in running backs
• 15.9% in wide receivers
  The remaining occur in other non-fantasy-relevant positions (tight end was not listed).¹

Unfortunately, data across several studies suggest a high recurrence rate for adductor strains in football and other sports.^1,4,5 Recurrence can be as high as 18%, most of which occur in the first two months back on the field.^1,4,5

There are identified risk factors that may predispose an athlete to an adductor strain:

• Previous history of an adductor strain
• Decreased hip range of motion
• Strength imbalance between hip adductors and abductors³,⁶

More recent research also highlights that reduced eccentric hip adduction strength (particularly during preseason testing) is a strong predictor of future groin injuries in football athletes.⁸ Additionally, poor lumbopelvic control during dynamic movement has been associated with increased injury risk.⁹. Furthermore, video motion analysis in elite soccer and Australian Rules football suggests that excessive internal rotation during cutting and deceleration moments increases groin strain risk, potentially due to increased mechanical demand on the adductor tendon.¹⁰

Groin injury return-to-sport outlook

The return-to-play outlook following a groin injury is typically not prolonged, as data on college football players shows that 62%-84% of players return to play within one week or less.^1,4 On the surface, it would be plausible that the grade of strain would influence the return to sport time. This may be the case to some degree; however, studies looking at elite soccer players show very little difference in return to sport time between grades I-II strains, with both averaging returning to playing in 2-4 weeks (Obviously, we are talking football here, but studies on NFL players are limited).⁵ However, in this same study, grade III injuries took 2-3 months to return to play. Therefore, functionally grade I-II injuries can be looked at similarly for a return to playing timeline; however, grade III injuries will likely take longer to get back on the field.  

Recent rehabilitation-focused studies emphasize that time-based clearance alone is outdated. Instead, return to sport should be based on meeting strength and movement benchmarks, particularly achieving ≥90% limb symmetry in isometric adduction force and full pain-free range of motion.¹¹. In professional soccer, where data is more robust, reinjury risk increases substantially if athletes return before reaching those benchmarks, even if they feel ready. It’s reasonable to infer similar patterns for NFL players given the comparable physical demands.

Groin injury rehab process

The initial portion of rehab will be focused on reducing pain and swelling, which is done through rest, ice, compression, elevation, and, depending on severity, possibly offloading via crutches.² During this phase, rehab will also focus on soft tissue treatments such as massage techniques, dry needling, and gentle stretching.² During this phase, it is important to identify factors that may have contributed to the onset of injury, such as stiffness in the ankles or hips and weakness in the hip or core muscles.^1,2,6

As pain begins to subside, the athlete can progress to stretching the adductor muscles and start strengthening them. Strengthening begins with isometrics, where the muscle engages but does not move the leg, and as tolerable progresses to concentric strengthening (muscle contracts and joint moves) and eccentrics (muscle contracts forcefully as it is stretching). During this phase, rehab will continue to focus on ankle mobility, hip mobility, glute, and core strength. It will also begin to incorporate balance exercises on unstable surfaces and/or on one leg. If the athlete has no pain with walking and a normal gait pattern, they may attempt gentle jogging, ideally on an anti-gravity treadmill. When all of these are tolerable and performed well, the athlete can progress to more sport-specific rehab.

When preparing to return to sport, a critical component is to ensure that the factors contributing to adductor strains are addressed. As mentioned above, these include a lack of range of motion at the hip and an imbalance of the hip adductors and abductor muscle strength.^3,6 Correcting these via stretching and strengthening exercises is a critical part of rehab. Additionally, stability on one leg should be close to equal to the uninjured leg. During sports, athletes are constantly on one leg when running, cutting, or jumping, and the ability to be stable on one leg will reduce the likelihood of re-injury. When these factors are addressed, it is generally safe to begin running, agility, and plyometrics, eventually progressing to sprinting and football-specific moves. 

Rehab Phases	Treatments	Criteria to Enter Phase
Early Phase	Rest, ice, compression, elevation, NSAIDs. Crutches if needed. Soft tissue work, dry needling, electrical stimulation (pain control). Ankle and hip mobility. Glute and core strength. Adductor isometrics if tolerable.	N/A first phase
Intermediate Phase	Soft tissue work, dry needling. Ankle and hip mobility. Glute and core strength. Adductor concentric and eccentric strength. Balance exercises. Gentle jogging (anti-gravity treadmill) if tolerable.	Little to no pain with adductor isometrics. Little to no pain with walking (for initiating running program).
Sports Specific	Full weight lifting. Progress to 100% speed running. Agility, plyometrics. Position specific drills.	No pain with adductor eccentrics. Adequate hip range of motion. Adequate adductor/abductor strength balance. Adequate single leg balance. No pain with jogging.

Generally speaking, adductor strains almost always respond well to conservative care, and surgery is very rare. In some instances, surgery may be impacted if a strain is severe and not healing well or if an avulsion fracture occurs where the tendon comes off of the bone and takes some of the bone with it.

References

1. Makovicka J, Chiabra A, Patel K, Tummala S, Hartigan D. A decade of Hip Injuries in National Collegiate Athletic Association Football Players: An Epidemiologic Study Using National Collegiate Athletic Association Surveillance Data. J. Athl. Train. 2019;54(5):483-488.
2. Sueki D, Brechter J. Orthopedic Rehabilitation Clinical Advisor. 1st ed. Maryland Heights, MO. Elsevier Inc.; 2010.
3. Candela V, Carli A, Longu U, et al. Hip and Groin Pain in Soccer Players. Joints. 2021;7(4):182-187.
4. Eckard T, Pauda D, Dompier T, Dalton S, Thorborg K, Kerr Z. Epidemiology of Hip Flexor and Hip Adductor Strains in National Collegiate Athletic Association Athletes, 2009/2010-2014/2015. Am J Sports Med. 2017;45(12):2713-2723.
5. Serner A, Weir A, Tol J er al. Return to Sport After Criteria-Based Rehabilitation of Acute Adductor Injuries in Male Athletes. Orthop J Sports Med. 2020;8(1).
6. Núnez J, Fernandez I, Torres A, et al. Strength Conditioning Program to Prevent Adductor Muscle Strains in Football: Does it Really Help Professional Football Players? Int J Environ Res Public Health. 2020;17(17):6408.
7. Branci S, Thorborg K, Nielsen M, et al. Radiological Evaluation of Groin Pain in Athletes. Br J Sports Med. 2020;54(10):602–608.
8. Ryan A, O’Donnell G, Delahunt E. The Association Between Preseason Hip Adduction Strength and Incidence of Groin Injuries in Elite Male Athletes. J Sci Med Sport. 2022;25(3):223–228.
9. Lee MJ, Callaghan MJ, McGregor AH. Core Stability and Athletic Performance: A Critical Review. J Sports Sci. 2020;38(17):1935–1944.
10. Duhig SJ, Shield AJ, Opar DA, et al. Mechanisms of Groin Injury in Sports: A Systematic Video Analysis. Sports Med. 2021;51(6):1243–1253.
11. Thorborg K, Serner A, Weir A, et al. Rehabilitation of Adductor-Related Groin Pain: Applying Current Clinical Evidence. Int J Sports Phys Ther. 2021;16(4):1100–1111.
12. Worner T, Thorborg K, Eek F. Movement Performance Tests in Return to Sport Decision-Making After Groin Injury. Int J Sports Phys Ther. 2023;18(1):68–76.