What Is an Adductor Strain?
Adductor strain — also referred to as muscular groin pain — is a partial or complete injury to the musculotendinous fibers of the hip adductor muscles, most commonly the adductor longus. It is the most frequent cause of groin pain in athletes, accounting for approximately 62% of all groin strains in sports populations.
The injury occurs predominantly in sports involving rapid changes of direction, acceleration, deceleration, and kicking — such as soccer, ice hockey, tennis, and combat sports. The typical mechanism is forced eccentric contraction of the adductors during sudden hip abduction or lateral change of direction, generating stress on the proximal myotendinous junction of the adductor longus.
The differential diagnosis of groin pain in athletes is broad and frequently challenging, as several structures converge in the inguinal region. Adductor strain may coexist with other causes of groin pain — such as hip pathology or sports hernia — making systematic evaluation essential.
Adductor Longus
The adductor longus muscle is the most frequently injured (62% of groin strains), with the proximal myotendinous junction as the predominant site.
Eccentric Mechanism
The injury typically occurs during forced eccentric contraction in abduction — change of direction, kick, lateral slide.
Copenhagen Protocol
The Copenhagen adductor exercise is the gold standard for prevention, with up to 41% reduction in adductor injury incidence in regular programs (Thorborg et al.).
Pathophysiology
The hip adductor muscles — adductor longus, adductor brevis, adductor magnus, gracilis, and pectineus — originate at the inferior pubic ramus and pubic symphysis, inserting along the linea aspera of the femur. The adductor longus is the most vulnerable due to its anatomic and biomechanical position: it has the largest mechanical lever during adduction, a relatively short proximal tendon, and a narrow myotendinous junction.
The main biomechanical risk factor is the adductor/abductor strength ratio. Prospective studies show that athletes with an adductor/abductor strength ratio below 80% have a significantly increased risk of strain (Thorborg et al., 2011). This imbalance is particularly common in soccer players, in whom the abductors are frequently stronger because of the repetitive kicking motion.
The injury typically occurs at the proximal myotendinous junction of the adductor longus — the transition zone between tendon and muscle belly, where force distribution is most heterogeneous. Strains are classified by grade: Grade I (rupture of a few fibers, without significant functional loss), Grade II (partial rupture with strength loss and functional limitation), and Grade III (complete rupture or avulsion, with functional disability).
Symptoms
The clinical presentation varies according to injury grade. In acute strain, the athlete frequently identifies the exact moment of injury — sudden groin pain during acceleration, change of direction, or kicking. In chronic or insidious forms, pain develops progressively and may be difficult to localize initially.
Symptoms of Adductor Strain
- 01
Groin pain (medial inguinal region)
Pain localized in the medial region of the groin, over the origin of the adductor longus at the pubic ramus or at the proximal myotendinous junction.
- 02
Pain on resisted hip adduction
Resisted contraction of the adductors (squeezing a ball between the knees) reproduces pain with high specificity.
- 03
Pain on passive hip abduction (stretching)
Passive stretching of the adductors strains the injured region, reproducing pain — especially in acute strains.
- 04
Pain when kicking, accelerating, or changing direction
Sports activities that actively recruit the adductors reproduce pain consistently.
- 05
Bruising on the medial thigh (grade II-III injuries)
Visible hematoma on the inner thigh, indicating significant fiber rupture with bleeding.
- 06
Weakness when squeezing the legs (positive squeeze test)
Loss of adductor strength, assessed by the squeeze test with a dynamometer at 45° hip flexion.
Diagnosis
The diagnosis of adductor strain combines clinical history (mechanism of injury, groin pain exacerbated by resisted adduction) with provocative physical examination. MRI is the gold standard to confirm the extent of injury and guide return-to-sport prognosis.
🏥Diagnosis of Adductor Strain
Fonte: Doha Consensus on Groin Pain (Weir et al., 2015)
Physical Examination
- 1.Squeeze test: pain on resisted adduction with hip at 45° flexion — most sensitive test for adductor pathology
- 2.Resisted adduction in supine: pain reproduced when adducting the lower limb against the examiner hand
- 3.Insertion palpation: pain on direct palpation of the adductor longus origin at the inferior pubic ramus
- 4.Passive stretching: pain on passive hip abduction with the knee extended (adductor stretching)
Imaging Studies
- 1.MRI: gold standard for grading (grade I-III), assessment of injury extent, and prognosis; muscle edema on T2/STIR
- 2.Ultrasound: dynamic assessment of the myotendinous junction, identification of intramuscular hematoma; good sensitivity for grade II-III injuries
- 3.Radiograph: assessment of heterotopic calcification, bone avulsion (rare), and exclusion of pubic osteitis (symphyseal irregularity)
DIAGNÓSTICO DIFERENCIAL
Diagnóstico Diferencial
Inguinal Hernia (Sports Hernia)
- Groin pain that worsens with abdominal effort
- Palpable bulge in the inguinal region may be present
- Pain on coughing or Valsalva maneuver
Testes Diagnósticos
- Palpation of the inguinal canal with Valsalva maneuver
- Resisted adduction typically painless (or less painful)
Pubic Osteitis
- Bilateral pain at the pubic symphysis
- Bone pain on symphysis palpation
- Frequently coexists with adductor pathology
Testes Diagnósticos
- Pain on direct palpation of the symphysis (not the muscle insertion)
- Radiograph with sclerosis and symphyseal irregularity
Pubic Ramus Stress Fracture
- Insidious groin pain in long-distance female runners
- Progressive pain with impact loading
- May radiate to groin and medial thigh
Testes Diagnósticos
- Localized bone pain at the pubic ramus
- MRI with bone marrow edema in the pubic ramus
Hip Labral Tear
- Deep anterior groin pain
- Hip clicking or locking
- Pain on internal rotation and hip flexion
Testes Diagnósticos
- Positive FADIR (flexion-adduction-internal rotation)
- MR arthrography with identifiable labral lesion
Piriformis Syndrome
Leia mais →- Deep gluteal pain with posterior radiation
- Worsens with prolonged sitting
- May radiate to the posterior thigh
Testes Diagnósticos
- Pain on piriformis palpation and resisted internal rotation
- Positive FAIR test (flexion-adduction-internal rotation in prone)
L2-L3 Radiculopathy
- Pain radiating from low back to groin and anterior thigh
- Possible sensory changes
- Associated low back pain
Testes Diagnósticos
- Neurologic examination with L2-L3 sensory changes
- Lumbar MRI with herniation or foraminal stenosis
Treatments
Treatment of adductor strain is predominantly conservative, with excellent results in most grade I and II cases. The therapeutic pillar is rehabilitation with progressive loading — progressing from isometrics to eccentric exercises and, finally, to sport-specific load. The Copenhagen adductor protocol, with strong evidence in the literature (Thorborg et al.), is integrated into both rehabilitation and prevention of recurrences.
Initial management involves pain control and relative protection of the injured region, but prolonged absolute rest is avoided — as with other musculotendinous injuries, early controlled loading accelerates recovery and improves the quality of tissue healing.
EXERCISES IN THE ADDUCTOR STRAIN REHABILITATION PROTOCOL
| EXERCISE | TARGET | PROTOCOL | NOTE |
|---|---|---|---|
| Adduction isometrics (squeeze) | Adductors — analgesic isometric loading | 5×45s at 60-70% of maximal load, 2×/day | Ball between the knees at 45° hip flexion; no pain during contraction |
| Copenhagen adductor (modified) | Adductors — submaximal eccentric loading | 3×6-8 each side, weekly progression | Modified version (knee support) initially; progression to the full version |
| Eccentric adduction with cable/elastic | Adductor longus — targeted eccentric loading | 3×10, 3s eccentric phase | Controlled abduction against resistance; focus on the lengthening phase under load |
| Side lunge | Adductors — functional loading with stretching | 3×8-10 each side, load progression | Progressive range; eccentric control on the lateral descent |
| Progressive change of direction | Neuromuscular integration — sport-specific | Sets of 6-10 repetitions, speed progression | Cutting drills at progressive speed; final stage before return to sport |
Rehabilitation Schedule
Phase 1
0-1 week (Grade I) / 0-2 weeks (Grade II)Protection and Isometrics
Pain control (cryotherapy, anti-inflammatories if indicated by the physician), adduction isometrics in a painless angle (squeeze with ball at 45°), painless gait as criterion for progression.
Phase 2
1-3 weeks (Grade I) / 2-6 weeks (Grade II)Eccentric Loading and Modified Copenhagen
Modified Copenhagen adductor (with knee support), eccentric adduction with cable, hip mobility. Acupuncture as an adjunct for pain control.
Phase 3
3-6 weeks (Grade I) / 6-10 weeks (Grade II)Functional Strengthening
Full Copenhagen, side lunge with progressive load, closed kinetic chain exercises. Criterion: painless squeeze test at 80% of contralateral strength.
Phase 4
4-8 weeks (Grade I) / 8-16 weeks (Grade II)Return to Sport
Changes of direction at progressive speed, running with acceleration/deceleration, sport-specific training. Copenhagen adductor maintained as ongoing prevention.
Acupuncture
Acupuncture can contribute as a complementary therapy to progressive loading rehabilitation in adductor strain, acting on modulation of groin pain and potentially favoring the muscle healing process. The approach combines local points in the inguinal region and medial thigh with regional and distal points for neuromodulation.
The point SP-10 (Xuehai), on the medial thigh above the patella, and LR-8 (Ququan), on the medial knee, are located along the meridians that course down the medial aspect of the lower limb and are relevant references for pain in this region. Ashi points over the injured myotendinous junction, identified by careful palpation, allow perilesional needling with potential local modulatory effect.
Electroacupuncture at a frequency of 2-4 Hz applied between points flanking the injury region can stimulate the release of endogenous opioids and inflammation modulators. Experimental evidence suggests that electroacupuncture may promote the expression of growth factors involved in muscle regeneration and reduce excessive scar fibrosis formation — although translation of these findings to clinical practice still requires more studies in humans.
ACUPUNCTURE POINTS IN ADDUCTOR STRAIN
| POINT | LOCATION | THERAPEUTIC FUNCTION |
|---|---|---|
| SP-10 (Xuehai) | Medial thigh, 2 cun above the patella | Modulation of the medial thigh; proximal point for adductor pain |
| LR-8 (Ququan) | Medial knee, at the end of the popliteal crease | Modulation of the liver meridian; regional point for groin pain |
| Ashi inguinal points | Over the injured myotendinous junction, palpation-guided | Direct perilesional needling; local analgesia and modulation |
| SP-6 (Sanyinjiao) | Medial leg, 3 cun above the medial malleolus | Confluence of the yin meridians; modulation of the medial lower limb |
| LR-3 (Taichong) | Dorsum of the foot, between 1st and 2nd metatarsals | Distal point of the liver meridian; modulation of pain along the inguinal pathway |
When to Seek Medical Help
Frequently Asked Questions about Adductor Strain
Adductor strain is an injury to the musculotendinous fibers of the hip adductor muscles — most commonly the adductor longus, which originates at the pubic ramus and is responsible for bringing the thigh toward the midline. Groin pain occurs because the proximal myotendinous junction (near the origin at the pubic bone) is the most vulnerable region, where eccentric traction forces during changes of direction and kicking generate concentrated stress.
Pubalgia is a broad term that encompasses several causes of pain in the pubic and inguinal region. Adductor strain (muscular pubalgia) is one of the most common causes, involving injury to the adductor fibers. Other causes include pubic osteitis (inflammation of the pubic symphysis), sports hernia, and hip pathology. The Doha Consensus (2015) recommends using specific terms instead of "pubalgia" to improve diagnostic and therapeutic precision.
The Copenhagen adductor is an eccentric strengthening exercise for the adductors performed in a side plank position, with the upper limb supported on a bench and the body sustained by adduction of the lower limb. It is considered the gold standard for prevention of adductor strains, with a meta-analysis demonstrating up to 41% reduction in groin injuries in teams that incorporate it into the regular warm-up. The modified version (knee support) allows safe progression in rehabilitation.
The time depends on the grade of injury: Grade I (microtears without significant functional loss) typically requires 1-3 weeks; Grade II (partial rupture with hematoma) requires 4-8 weeks; Grade III (complete rupture) may require 3-4 months or surgical intervention. Adherence to the progressive loading protocol and inclusion of prevention exercises (Copenhagen) directly influence return time and risk of recurrence.
Prevention is based on three pillars: (1) regular adductor strengthening with the Copenhagen adductor exercise in the warm-up (2-3x/week); (2) maintenance of the adductor/abductor strength ratio above 80%, periodically assessed with the squeeze test; and (3) management of training load, avoiding abrupt increases in volume and intensity. Preseason screening with the squeeze test identifies at-risk athletes who benefit from intensified preventive programs.
Acupuncture can contribute as a complementary therapy to rehabilitation, acting on modulation of groin pain and potentially facilitating adherence to the progressive exercise program. Electroacupuncture in the perilesional region may promote endogenous analgesia and modulate the inflammatory process. The greatest benefit is to facilitate the performance of the Copenhagen adductor and eccentrics at the appropriate therapeutic dose, especially in the early phases of rehabilitation. A medical acupuncturist can integrate this approach into the treatment plan.
Surgery is rarely necessary and reserved for: complete ruptures (Grade III) with significant tendon retraction, bone avulsions of the pubic ramus, and cases of failure of conservative treatment for 3-6 months. The most common procedure is reinsertion (repair) of the adductor tendon to the pubic ramus. Most athletes return to competition within 3-4 months after surgical repair, with rates of return to pre-injury level varying between 75-90% in the available literature.
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