What is adductor strain?

Adductor muscles are a group of five muscles located in the inner thigh. These muscles help to bring the legs close to each other and stabilise the pelvis during standing and walking.

Strain, injury or imbalance of the adductor muscles is a common cause of inner thigh and groin pain, especially amongst individuals who are physically active or in competitive sports. Soccer players are commonly affected and as per one study adductor strains account for 10% of all injuries in soccer players. Other sports where associated with adductor injuries include hockey, basketball, tennis, figure skating, baseball, horse riding and karate. Tight adductor muscles can lead to hip, knee and back pain and affect our gait. Of all the adductor muscles, one called adductor longus is the one most frequently injured.

What are the symptoms of adductor sprain?

Common presenting features include:

• Groin, inner thigh and lower abdominal pain. In some cases, the pain is intense at the beginning of athletic activity and is later replaced by a dull ache
• Pain on sitting cross legged or when with coughing/ sneezing
• Pain on activity such as

• Lifting one leg as while stepping down from height or getting out of car
• Turning or changing direction
• Walking. In mild cases pain may be provoked by more strenuous activities such as running, kicking or performing lunges 

• Bruising or swelling in the painful area in severe cases
• Localised tenderness in the upper inner thigh, close to where the adductor muscles attach to the pubic bone 

Adductor strains are classified as

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

What causes adductor strain?

Adductor strains form a significant proportion of groin injuries. In a study among European soccer players, adductor muscle injuries were the second most common (23%) after hamstrings (37%). Risk factors contribution to injury include

• Previous hip or groin injury
• Overuse, fatigue and muscle imbalances
• Weak adductors with poor flexibility
• Poor hip/pelvic stability and strength
• Running on hard surfaces, excessive running
• Footwear
• Training associated factors such as inadequate stretching, and lower levels of sport-specific training changes in training intensity, volume or type of training
• Age- tendons become less able to absorb force as they age
• Biomechanical abnormalities including excessive pronation or leg-length discrepancy
• Genetic factors such as poor collagen

Adductor sprain can be of sudden or gradual onset. Acute injury is associated with sporting actions such as suddenly changing direction at speed, sudden acceleration in sprinting, sliding sideways or kicking. One study analysed the videos of acute adductor injuries in professional male football players and found that majority of injuries occurred in non-contact situations (71%). Common injury actions included change of direction (35%), kicking (29%), reaching (24%) and jumping (12%).

How is this condition diagnosed?

Diagnosis can be usually made clinically. MRI is used for confirming the diagnosis and assessing severity especially in chronic injuries unresponsive to conservative treatment modalities. Ultrasound scan is the alternative imaging option.

MRI Scans can give prognostic information as tears involving >50% of the cross-sectional area, tissue fluid collection, or deep muscle tears indicate more severe injury with prolonged recovery. The location of the tear is important as tears at the junction of the muscle with tendon (musculotendinous junction) can be more aggressively rehabilitated compares to one close to the joining of the tendon with bone, due to differences in the blood supply of the two areas. Tendons can be viewed as ropes tying the muscles to the bones. The musculotendinous junction is the most common site of injury in a muscle strain.

What are the treatment options for adductor strain?

Once the diagnosis has been established, treatment and prognosis are influenced by factors such as

• Location of tear as those at the junction of the muscle with the bone can be dealt by aggressive rehabilitative treatment
• Degree of strain/ tear
• Duration of symptoms- acute or chronic
• Presence of any biomechanical abnormalities such as muscular imbalances, leg length discrepancy

Acute injuries are initially treated with rest, ice, compression anti-inflammatory drugs and physical therapy with further management dependant of factors discussed earlier. Early treatment is recommended, and injections are used as required.

Education about load management and avoiding provoking factors is important. Activities like running can be replaced with swimming, walking, cycling as having baseline activities is preferred to absolute rest. Specific and individualised exercise programs have a role. A slowly progressive loading program can be used to improve strength and control of adductors, pelvis and lower limbs. The aim of the treatment initially is preventing further injury and inflammation and proving an optimal environment for healing to take place. As recovery occurs, this changes to restoration of range of motion and prevention of atrophy and then subsequently to regaining strength and flexibility.

Injections

This option is considered for individuals’ not responding to conservative measures. Injections are used in combination with physical therapy can help in confirming the diagnosis, providing early, lasting relief and possibly facilitation early return to usual activities. The options include

• Steroid injections
• PRP with or without needle tenotomy
• Obturator Nerve block

Regardless of whichever option is used, ultrasound guidance is valuable in improving accuracy and reducing complications. Sometimes injections of the muscle in the lower abdomen (rectus abdominis muscle) are performed at the same time.

Steroid injections: There are quick to work, commonly performed injections. Steroids have anti-inflammatory effects and it may be all that is required to reduce the pain and help you actively engage with physical therapy. Some studies have shown better effects if the duration of symptoms is less that 6 weeks and hence the importance of early treatment.  Post injection graded increase in activities can be commenced once the pain remains controlled for two weeks.

Platelet Rich Plasma (PRP): PRP injections are commonly used for treatment of tendinopathy and the evidence supporting their use is slowly accumulating. The procedure involves spinning one’s blood in a special machine which separates the platelets (containing the growth factors) from the other blood components. This concentrated platelet layer is then injected into the problem area to induce tissue healing. These injections take time to work with benefits becoming apparent 6 to 12 weeks after treatment. PRP injections are frequently used in combination with needle tenotomy which essentially implies repeated puncturing of the tendon to promote blood flow to the area and induce long-term healing.

Obturator Nerve Block: This injection can have added effect on top of the injections discussed previously. Obturator nerve supplies most of the adductor muscles and hence blocking this nerve can help in reducing the pain signals being transmitted. Injury or compression of the nerve leads to symptoms similar to adductor sprain and is addressed as obturator neuralgia.  Obturator neuralgia can also be secondary to adductor strain and is a known cause of exercise induced groin, inner thigh pain. In this situation obturator nerve block can be especially useful.

Surgery: This option may be considered for acute complete tears with limb weakness or chronic tears with non-satisfactory response to other treatment modalities for a minimum of 6 -12 months. Surgery involves tendon release or dividing the tendon (tenotomy) and this may help to reduce the pain

Restarting activities: Return to play and activity is guided by symptom recovery as well as progress with treatment. Too soon a return is risk factor for repeat injury, which can cause chronic symptoms. Generally, after an acute strain return to sports is recommended on regaining 70% of strength and a painless range of motion. This can be usually achieved between 4 to 8 weeks, although can take up to 6 months chronic injuries. Maintaining adductor strength at a minimum of 80% of abductor strength has been shown to reduce adductor injuries.

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