Adductor Strain 

An adductor (groin) strain is a common problem among many individuals who are physically active, especially in competitive sports. The most common sports that put athletes at risk for adductor strains are football, soccer, hockey, basketball, tennis, figure skating, baseball, horseback riding, karate, and softball.^[1]

Hip adductor injuries occur most commonly when there is a forced push-off (side-to-side motion). High forces occur in the adductor tendons when the athlete must shift direction suddenly in the opposite direction. As a result, the adductor muscles contract to generate opposing forces.

One common cause of adductor strain in soccer players has been attributed to forceful abduction of the thigh during an intentional adduction. This type of motion occurs when the athlete attempts to kick the ball and meets resistance from the opposing player who is trying to kick the ball in the opposite direction. To a lesser extent, jumping also can cause injury to the adductor muscles, but more commonly, it involves the hip flexors. Overstretching of the adductor muscles is a less common etiology.

The hip adductors are a powerful muscle group. They consist of the adductor magnus, minimus, brevis, and longus. The gracilis and pectineus muscles also are included. All of the adductor muscles are innervated by the obturator nerve (L2-L4) except the pectineus, which is innervated by the femoral nerve (L2-L4). The adductor magnus also is innervated by the tibial nerve (L4-S3).^{[2, 28, 30]}

The origins and insertions of each of the hip adductors are noted below:

• Adductor magnus/minimus: origin is the inferior pubic ramus/ischial tuberosity; insertion, linea aspera/adductor tubercle
• Adductor brevis: origin is the inferior pubic ramus; insertion, linea aspera/pectineal line
• Adductor longus: origin is the anterior pubic ramus; insertion, linea aspera
• Gracilis: origin is the inferior symphysis/pubic arch; insertion, proximal medial tibia
• Pectineus: origin is the pectineal line of pubis; insertion, pectineal line of femur

The musculotendinous junction is thought to be the most common site of injury in a muscle strain. Studies in muscle physiology demonstrate that the sarcomeres near the junction are less elastic than those found at the central portion of the muscle.^[3]

The adductor tendons have a small insertion area that attaches to the periosteum-free bone. This transitional zone is characterized by a poor blood supply and rich nerve supply, explaining the high level of perceived pain and poor healing characteristics of adductor strains.

The musculotendinous junction is likely to be vulnerable to indirect muscle injury that results from excessive force. Muscle strain injury has been characterized as occurring in response to forcible stretching of a muscle, most commonly while the muscle is activated. When the muscle is activated, muscle strain injury occurs, most often during eccentric (lengthening) contraction.

Injury to the hip adductors most commonly occurs following forced push-off (side-to-side motion). An extreme amount of stress is placed on the adductor tendons when, because of the athlete's momentum, a large amount of force is applied to one side in the sagittal plane and the adductor muscles must contract rapidly to shift the force to the opposite direction.

Rapid adduction of the hip against an abduction force (eg, changing direction suddenly in tennis), acute forced abduction that puts an unusual stretch on the tendon (eg, a rugby tackle), and a sudden acceleration in sprinting are the most common mechanisms of injury. Jumping is involved to a lesser extent than abduction and is associated more commonly with hip flexor strains. Overstretching of the adductor tendons is a much less common cause.^{[4, 5, 6]}

Failure to stretch the adductor muscles properly puts them at increased risk for injury. Weakness of the adductor muscles is a common problem that puts these muscles at increased risk for injury, as the load to failure is much less in weaker muscles.

Muscle strain is the most frequent injury observed in sports. Up to 30% of office visits in a primary care sports medicine practice are attributed to muscle strain. As with other musculotendinous injuries, increased age is related to elevated risk for strains due to reduced elasticity of connective tissue.

Scandinavian soccer studies have reported groin injury rates of 10-18 injuries per 100 soccer players each year. Lovell studied 189 cases of chronic groin pain in which he attributed 30% to adductor injuries.^[7] The Renstrom and Peterson study found the adductor longus was responsible for 62% of groin injuries.^[8] Injuries to the groin account for 5% of all soccer injuries and 2.5% of karate injuries.

Improper management of acute adductor strains or returning to play before pain-free sport-specific activities can be performed may lead to chronic injury. According Renstrom and Peterson, 42% of athletes with groin muscle-tendon injuries could not return to physical activity after more than 20 weeks following the initial injury.^[8] This prolonged length of time seems to indicate the importance of proper management of these injuries in the acute stage.

The patient needs to be educated on proper treatment following an acute groin injury. PRICE (protection, rest, ice, compression, and elevation) needs to be emphasized to ensure that swelling is reduced. In the acute stage, inform patients to avoid activities that may be harmful and to promote increased blood flow to the adductor muscles by use of hot packs, hot showers, or massage. The athletic trainer and/or physical therapist should instruct the patient in proper exercises to rehabilitate the adductor muscles and enable the patient to return safely to participation in a sport or activity.

As is the case in many injuries involving athletes, outside influence on the physician to return the athlete to play before being medically ready can be a problem. The best interest of the player must take precedence in this situation. Returning players with an adductor injury to their sport too quickly can have a detrimental effect on a future career. Adductor injuries have a tendency to become chronic when not properly treated.

For excellent patient education resources, visit the Sports Injury Center, as well as Muscle Strain.