What is an Adductor Muscle (Groin) Strain?
An adductor muscle strain is an acute injury to the groin muscles on the medial aspect (inside) of the thigh. Although several different muscles can be injured, the most common are the Adductor Longus, Medius, and Magnus, and the Gracilis.
Strains reflect tears of the muscle-tendon unit, due to forceful contraction of the muscles against resistance, often during an eccentric load. Eccentric refers to a muscle contraction while the muscle is lengthening, versus concentric, in which the muscle shortens during the contraction. Most weight-lifting involves concentric contraction; “Negatives” during bench press is an example of an eccentric contraction.
Tears can occur at muscle origin or insertion, at the muscle-tendon junction, or within the belly of the muscle(s). Most commonly, tears occur at the muscle-tendon junction. Uncommonly, the tendon injury occurs at the site of its’ bony attachment.
Strains can be graded I-III based upon their severity. Grade I involves a mild strain with some injury, bleeding, tenderness, but no significant fiber disruption. A Grade II injury involves injury to the muscle-tendon fibers but the overall integrity of the muscle-tendon unit is preserved. A Grade III injury involves disruption leading to a loss of overall tendon integrity. Most adductor muscle strains are Grades I or II.
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How does it occur?
Most commonly, strains occur during acute muscle contraction, such as when kicking, pivoting or skating. Factors that can predispose a patient to injury include failure to warm up, properly stretch, or fatigue from overuse.
Risk increases with:
- Sports involving acceleration such as sprinting, soccer, football, hockey.
- Sports with repeated movements such as soccer, martial arts, and gymnastics.
- Failure to warm up, stretch or be properly conditioned.
What are the symptoms?
- Sudden onset of pain, sometimes accompanied by the sensation of a pop in the inner thigh.
- Inability to continue activity after initial onset of pain
How is it diagnosed?
- History and physical exam are usually sufficient to establish the diagnosis
- Physical findings include tenderness to palpation (touch), bruising over the inner thigh and sometimes, swelling and warmth over the site of injury. With severe tears there may be a palpable defect over the site of the injury, though this is uncommon.
- Range of motion testing of the hip is usually normal, but pain is usually reproduced when the patient is asked to contract the muscles. In this case, asking the patient to bring their leg towards midline (adducting their leg) reproduces pain and is usually accompanied by weakness.
Are any special tests used to diagnose an adductor muscle strain?
Special tests are typically unnecessary.
X-rays are almost always negative, but are appropriate in cases in which there is tenderness at the site of bony insertion, or in skeletally immature athletes/patients. In children, attachment sites of muscle/tendon units are vulnerable to fracture and are weaker than the muscle/tendons.
MRI is indicated in elite professional athletes, in which precise knowledge of injury location and extent may help in estimating return to activity, or in rare cases, help identify any cases which may require operative treatment.
How is it treated?
Most adductor muscle strains respond to conservative treatment. Initial treatment includes activity modification, which may temporarily include crutches. Ice and anti-inflammatory medication are appropriate for acute muscle strains. As symptoms improve, gentle stretching and strengthening exercises are appropriate. Your physician may recommend a physical therapy program to aid with these exercises.
Surgery for these injuries is rarely necessary. Avulsion injuries, in which the tendon is pulled away with its bony attachment, may require operative reattachment. Some cases of complete muscle tendon tears may require surgery. Repair involves an open incision over the site of injury and reattachment of the tendon origin, or suture repair of torn soft tissue. Surgery is also necessary in patients with chronic pain whose symptoms do not respond to conservative treatment.
When can you return to your sport/activity?
- Time out of activity varies greatly with the extent of the injury. Most strains start to improve within 10-14 days, and continue to improve over many months.
- A severe strain may require crutches for several weeks and take a longer recovery period.
- Some patients will continue to struggle with mild chronic symptoms of pain for more than 6 months.
How can an Adductor Muscle Strain be prevented?
- Most (but not all) strains can be avoided through proper warm up and stretching before activity.
- Stretching should include the hip, thigh and knee
- If injury does occur, avoid premature return to activities.