A Core Muscle Injury (CMI) is a soft tissue injury affecting the lower abdominal wall and groin, commonly seen in athletes participating in high-intensity sports. Unlike a sudden muscle strain, a CMI typically develops over time due to repetitive stress placed on the muscles and tendons connecting to the pelvis. Diagnosis can be difficult because the pain is often vague and may mimic other conditions in the region.
Anatomy and Terminology
A Core Muscle Injury is a musculotendinous strain or tear occurring in the peripubic region, the area surrounding the pubic bone. The injury involves structures that insert directly onto the pubic bone, creating tension between opposing muscle groups. The most frequently involved structures are the lower abdominal muscles (specifically the rectus abdominis and the conjoint tendon) and the adductor muscles of the inner thigh (particularly the adductor longus).
The condition is also widely known as “athletic pubalgia” or a “sports hernia,” though Core Muscle Injury (CMI) is the preferred term. The name “sports hernia” is misleading because a true hernia involves the protrusion of an organ through a weakness in the abdominal wall, often presenting as a visible bulge. A CMI, by contrast, is solely a soft tissue injury—a tear or micro-tear of the muscle or tendon—and lacks the characteristic bulge of a true hernia.
The injury is fundamentally a disruption of the shared attachment point on the pubic bone. The abdominal muscles pull upward while the adductor muscles pull downward, and injury occurs when this delicate balance is overwhelmed by force. The resulting damage can include tendinopathy of the abdominal or adductor tendons, or a defect in the posterior wall of the inguinal canal.
How Core Muscle Injuries Occur
Core Muscle Injuries result from repetitive, high-velocity movements requiring explosive twisting and turning of the torso and legs. Sports such as ice hockey, soccer, football, and rugby involve frequent cutting maneuvers and powerful kicking or sprinting, placing extreme forces on the lower abdominal and adductor muscles. The injury is the cumulative result of continuous microtrauma near the pubic symphysis, rather than a single, acute event.
The mechanism involves a rapid, forceful contraction of the abdominal muscles occurring simultaneously with an opposing contraction of the adductor muscles. This uncoordinated pull generates significant shearing stress at the shared attachment point on the pubic bone, causing tissues to weaken, strain, or tear over time.
The primary symptom is a deep, persistent pain in the groin or lower abdomen that is difficult to localize. This pain increases dramatically during athletic activities, such as sprinting, kicking, or sudden changes in direction, but subsides when the athlete rests. Exertions that increase intra-abdominal pressure, like coughing, sneezing, or sitting up, can also aggravate the discomfort.
Recognizing and Addressing the Injury
Diagnosis begins with a detailed patient history and a physical examination focused on the groin and hip area. A physician looks for tenderness over the pubic bone and adductor tendons, often performing specific tests like a resisted sit-up or an adductor squeeze test to provoke pain. Since symptoms overlap with many other conditions, the diagnostic process involves ruling out sources of pain such as hip joint issues, nerve entrapment, or a true inguinal hernia.
Imaging studies are used to confirm the diagnosis and assess soft tissue damage. Magnetic Resonance Imaging (MRI) is preferred because it provides detailed images of muscles, tendons, and ligaments, though it may not always show the full extent of the injury. Ultrasound can also be used as a dynamic tool to visualize tissues under stress.
Initial treatment involves conservative management, including rest, activity modification, and anti-inflammatory medications. Physical therapy is a component of this approach, focusing on strengthening the core and hip muscles to restore stability and balance. This non-operative regimen is typically attempted for six to twelve weeks.
If symptoms persist despite conservative care, surgical intervention may be considered to repair the torn or weakened tissues. Surgery typically involves reattaching the damaged abdominal muscles to the pubic bone and sometimes addressing the adductor muscles through a release procedure. Following surgery, a structured rehabilitation program is essential, with a return to full athletic activity typically occurring around three months post-operation.