Adductor Strain

Etiology

Adductor strain is a common injury among soccer and hockey players. Other common sports related to adductor strain include football, basketball, tennis, figure skating, baseball, horseback riding, karate, and softball. Risk factors include previous hip or groin injury, which is likely the greatest risk, as well as age, weak adductors, muscle fatigue, decreased range of motion, and inadequate stretching of the adductor muscle complex. Biomechanical abnormalities including excessive pronation or leg-length discrepancy can also contribute.[3][4]

Suddenly changing direction causes rapid adduction of the hip against an abduction force, putting exaggerated stress on the tendon. Sudden acceleration in sprinting is the most common mechanism of injury. Jumping and overstretching the adductor tendon are less common causes.

Epidemiology

Muscle strain is the primary injury among athletes, accounting for up to 31% of visits. Among European soccer players, adductor muscle injuries were the second most commonly injured muscle group (23%) behind hamstrings (37%).

In another study of soccer players, adductor pain/strain represents anywhere from 9% to 18% of all injuries. In sub-elite, male soccer players, adductor strain accounted for 51% of all groin pain.

Pathophysiology

Most muscle tendon strains occur while the muscle is being forcibly stretched while being concentrically contracted. The greatest eccentric tension is placed on the adductor complex when the leg is in external rotation and abduction. Adductor injuries typically occur when the athlete pushes off in the opposite direction. As a result, the adductor muscles contract to generate both eccentric and concentric opposing forces. The dominant leg is more commonly injured and more likely to sustain significant injury.

For example, a soccer player trying to kick a ball with an externally rotated leg using the inside of their foot. If their leg swinging in adduction meets a significant resistive abductive force such as another player, this can place a significant load on the adductor complex leading to injury.

The musculotendinous junction is the most common site of injury in a muscle strain. The adductor tendons have a small insertion zone which is characterized by an area of poor blood supply and rich nerve supply which helps explain the increased degree of perceived pain.

The adductor longus is the most commonly injured muscle and accounts for 62% to 90% of cases. It is hypothesized that this occurs due to its low tendon to muscle ratio at the origin. Rugby players with an adductor-abductor strength ratio of less than 80% are 17 times more likely to sustain an adductor injury.[5]

History and Physical

Patients will often describe a sudden onset of pain during a specific activity as opposed to a more insidious onset. They will describe the pain as severe and in the groin region or medial thigh that is worse with activity.

Individuals can sustain injury anywhere along the medial compartment of the thigh along the adductor complex. The clinician may observe bruising or swelling in moderate to severe injuries. Typically, there is an area of point tenderness or localized tenderness. They may be tender along the proximal attachment of the pubic ramus. The patient will have pain with resisted adduction of the hip or with passive stretching. They may have decreased strength secondary to pain or depending on the degree of injury, this strength deficit may be due to muscle or tendon rupture or avulsion injury.

Evaluation

Radiographic evaluation is the initial modality of choice for suspected adductor strain. Anteroposterior views of the pelvis and frog-leg view of the affected hip are recommended as initial imaging studies. In most patients, these images will be normal in appearance; however, occasionally one may observe an avulsion injury. These images can also help evaluate for other causes of groin pain such as osteitis pubis, apophyseal avulsion fractures, and pelvic or hip stress fractures.

If further imaging is needed, magnetic resonance imaging (MRI) is recommended. This is likely to show muscle edema and hemorrhage at the site of injury. If there is a bony injury, this will be better elucidated on the MRI.

Musculoskeletal ultrasound can further visualize the tendon and bony attachment sites, muscles, ligaments, and nerves. Ultrasound can be used to identify the area and extent of the injury and used to evaluate periodically during the recovery phase.

Treatment / Management

Most adductor strains are managed conservatively. Initial management will include relative rest from sports, ice, compression, analgesia, and physical therapy. Analgesia typically includes acetaminophen and non-steroidal anti-inflammatory medications. The rehabilitation program should include stretching the range of motion and strengthening of the affected leg and core accompanied by a gradual return to sport. Acute injuries may return as quickly as 4 to 8 weeks while chronic strains may take many months to achieve desired results.[6][7][8](B3)

In addition, other treatment modalities may be available for refractory cases. This includes corticosteroid injection into the adductor complex and needle tenotomy, both of which are at the discretion of the consulting clinician and typically performed under ultrasound guidance.

Occasionally, surgical management is indicated. There are no clear guidelines on which injuries require surgical management. Potential indications include poor recovery with conservative management with full-thickness tears or avulsion injuries with the persistent weakness of the affected limb.

Differential Diagnosis

The musculoskeletal differential diagnosis of groin pain is broad and includes tendonitis (iliopsoas, rectus femoris), bursitis (iliopsoas), athletic pubalgia (sports hernia, sportsman’s hernia, pre-hernia complex, Gilmore groin), hip joint pathology (osteoarthritis, femora-acetabular impingement, slipped capital femoral epiphysis, avascular necrosis), osteitis pubis, sacroiliac dysfunction, neuropathic pain (radiculopathy, sciatica), and mechanical low back pain.

Nonmusculoskeletal causes of groin pain include urologic disorders, malignancy, gastrointestinal disorders, sexually transmitted infections, and, in women, gynecologic disorders.

Staging

 Adductor strain has a 3-tier classification system.

• First degree: Pain without significant loss of strength or range of motion
• Second degree: Pain with loss of strength
• Third degree: Complete disruption of muscle or tendon fibers with loss of strength

Prognosis

The prognosis for adductor strains is generally favorable. Most athletes will return to play with minimal pain and normal function if provided appropriate relative rest and rehabilitation. If they return to play too soon or are inadequately rehabilitated, their pain may lead to chronic injury.

Renstrom et al. found that 42% of athletes with muscle-tendon groin injuries were not able to return to physical activity more than 20 weeks after the initial injury. However, an active training program directed at strengthening and conditioning of muscles of the pelvis and especially the adductor muscles is very effective at treating patients with long-standing, adductor-related groin pain.[9][10]

Complications

Complications of adductor strains primarily include acute pain and missed playing time. In some cases, the pain may be more chronic with associated weakness and inability to return to sport.

Because sport-related groin injuries are a significant contributor to missed playing time, prevention is essential in maintaining a healthy athlete. Prevention programs are directed at adductor strengthening. Maintaining adductor strength at a minimum of 80% of abductor strength has been shown to reduce adductor injuries. One program among NHL players identified as having weak abductors participated in a 6-week preseason strengthening program which reduced adductor strains from 3.2 injuries per 1000 player-game exposures to 0.71.