MSK · EP 29 · GROIN
Before You Listen
Episode Setup
- Topic in one line: the groin pain differential and leg length discrepancy. The groin is a deceptively crowded anatomic neighborhood where adductor strain, athletic pubalgia (sports hernia), osteitis pubis, hip flexor strain, pediatric apophyseal avulsion fractures, true inguinal hernia, hip labral tear, and femoral neck stress fracture all overlap. Leg length discrepancy (LLD) is split into true (bony), apparent (pelvic obliquity), and functional (contracture/postural) categories with distinct measurement techniques and treatment thresholds.
- Prerequisites: hip and pelvic anatomy (anterior superior iliac spine [ASIS], anterior inferior iliac spine [AIIS], pubic tubercle, pubic symphysis, ischial tuberosity, lesser trochanter), the adductor compartment muscles, the iliopsoas, the conjoint tendon, the inguinal canal, gait phases, and the Salter-Harris growth plate framework from MSK-27.
- Runtime: 48 minutes 55 seconds.
Vignette. A 26-year-old professional hockey player presents with four months of progressive right lower abdominal and inguinal pain. The pain began insidiously, worsens with skating and shooting, and improves with rest. On examination, the inguinal canal is normal bilaterally with no palpable hernia and no cough impulse. There is tenderness on deep palpation through the right external ring. Pain is reproduced with resisted sit-ups and Valsalva maneuver. There is mild tenderness along the right adductor longus origin. MRI shows edema at the right pubic symphysis and enthesopathy at the rectus abdominis insertion.
What is the diagnosis, what is the proposed mechanism of injury, what is the most common misdiagnosis in this clinical picture, what is the expected response rate to a structured 6-8 week conservative rehabilitation program, and how does the location of tenderness distinguish this entity from osteitis pubis and from a pure adductor strain?
(Answer at the end of this chapter)
Section 1: Adductor Strain — The Most Common Groin Injury
Bottom line: adductor strains are the most common cause of athletic groin pain (~10% of all sports injuries); the adductor longus at its proximal pubic tubercle insertion is the most commonly torn structure; tenderness sits at the pubic tubercle or along the adductor muscle belly with pain on resisted adduction (the squeeze test); the Copenhagen adduction exercise has level 1 evidence for prevention; and the adductor-to-abductor strength ratio below 0.80 is a validated modifiable risk factor.
Adductor strains are the most common cause of groin pain in athletes, accounting for approximately 10% of all sports injuries. They are most prevalent in soccer, hockey, football, and equestrian sports, all of which demand rapid changes of direction, forceful kicking, and powerful adduction against resistance. The injury is partial or complete tearing of the adductor muscle-tendon unit, most commonly the adductor longus at its proximal attachment on the pubic tubercle and inferior pubic ramus. The mechanism is typically eccentric overload during forced abduction of a planted leg or rapid acceleration and deceleration with change of direction. The adductor longus is the most commonly injured because it has the smallest cross-sectional area relative to the force demands placed on it, and its proximal attachment concentrates stress at the bone-tendon junction.
Risk factors include previous adductor injury (the strongest predictor of recurrence), inadequate warm-up, weak adductors relative to abductors with an adductor-to-abductor strength ratio of less than 0.80 (a validated modifiable risk factor), and limited hip abduction range of motion. Clinical presentation includes acute or insidious groin pain that worsens with activity. On examination, there is tenderness at the pubic tubercle or along the adductor muscle belly, pain with resisted hip adduction (assessed using the squeeze test where the patient squeezes the examiner’s fist between their knees), and pain with passive hip abduction stretching. Grading follows the standard muscle strain classification: grade 1 (mild pain, no strength loss), grade 2 (moderate pain, partial tear, measurable strength loss), grade 3 (complete tear, palpable defect, significant weakness) (Figure 29.1).
Source: Alfred W. Hughes, A Manual of Practical Anatomy (1901), Wikimedia Commons, Public Domain
Imaging with MRI confirms the diagnosis and characterizes tear extent. Ultrasound can identify acute tears but is operator-dependent. Treatment is conservative: relative rest, ice, NSAIDs, and progressive rehabilitation emphasizing eccentric strengthening and neuromuscular control. The Copenhagen adduction exercise has level 1 evidence for prevention of adductor injuries in soccer players and is one of the most well-validated injury prevention exercises in sports medicine. The athlete lies on the side with the top leg supported on a bench or by a partner and the bottom leg adducts against gravity, lifting from the floor. Return to play is guided by pain-free resisted adduction at full strength and sport-specific functional testing. Surgical repair is reserved for complete proximal avulsions with significant retraction. The rehabilitation timeline follows the injury grade: grade 1 in 1-2 weeks, grade 2 in 3-6 weeks, grade 3 complete tears in 2-3 months, and surgical candidates with significant retraction in 4-6 months.
An anatomic point worth knowing: the adductor magnus has dual innervation. The adductor portion is innervated by the obturator nerve, while the hamstring portion (which arises from the ischial tuberosity and inserts on the adductor tubercle of the femur) is innervated by the tibial division of the sciatic nerve. The gracilis is the only adductor that crosses both the hip and knee joints and is one of the three tendons of the pes anserinus insertion on the proximal medial tibia (along with sartorius and semitendinosus).
High Yield — Adductor Strain
- Most common cause of athletic groin pain (~10% of sports injuries).
- Adductor longus at the pubic tubercle is the most commonly torn structure.
- Squeeze test + resisted adduction pain + pubic tubercle tenderness = positive triad.
- Copenhagen adduction exercise has level 1 evidence for prevention.
- Adductor-to-abductor strength ratio <0.80 is a validated modifiable risk factor.
- Adductor magnus dual innervation: obturator (adductor portion) + tibial division of sciatic (hamstring portion).
It has a relatively small cross-sectional muscle belly area compared to the massive explosive force demands placed on it when an athlete is sprinting or cutting laterally. You have all of this mechanical stress and kinetic energy funneling up from the leg, and it gets concentrated right at that tiny bone tendon junction.
— MSK-29 podcast, ~4:54