Adductor Longus
| |
| Adductor Longus | |
|---|---|
| Muscle Type | |
| Origin | External surface of body of pubis (triangular depression inferior to pubic crest and lateral to pubic symphysis) |
| Insertion | Linea aspera on middle one-third of shaft of femur |
| Action | Adducts thigh; assists in hip flexion (especially from extended position) and medial rotation |
| Synergists | |
| Antagonists | |
| Spinal innervation | L2, L3, L4 |
| Peripheral Innervation | Obturator nerve (anterior division, L2–L4) |
| Vasculature | Obturator artery; deep femoral (profunda femoris) artery |
The adductor longus is a long, triangular muscle in the medial compartment of the thigh. It lies most anterior of the adductor group and forms the medial border of the femoral triangle. As its name suggests, it adducts the thigh, pulling the leg toward the midline. It also assists in hip flexion and medial rotation to a smaller degree. The adductor longus is often involved in "groin pulls" in athletes and is an important surface landmark for surgical approaches and catheterizations (because the femoral neurovascular bundle lies just lateral to it).
Structure
Adductor longus is a strap-like muscle with a broad origin and narrow insertion, classified in the medial (adductor) compartment of the thigh. It is superficially located, just below the pectineus and anterior to the adductor brevis and magnus. Its orientation is oblique, running inferolaterally from the pubis to the femur.
Origin
It arises from the body of the pubis, specifically the anterior aspect of the pubis below the pubic tubercle (inferior to the pubic crest). This origin is just lateral to the pubic symphysis. It's often described as arising by a strong tendon from the superior pubic ramus (front of pubic body).
Insertion
The adductor longus inserts on the middle third of the linea aspera of the femur, on its medial lip. In other words, it attaches to the rough ridge on the posterior femur, between the insertions of adductor brevis (above) and adductor magnus (below). This insertion spreads a bit vertically but is focused in that mid portion of the thigh. Because it doesn’t extend as far distally as magnus, it is shorter in functional length.
Action
Its primary action is adduction of the thigh at the hip – bringing the leg toward the midline. It also contributes to hip flexion, particularly from an extended hip position (e.g., initiating swing phase of gait or during kicking). Once the hip is flexed ~70 degrees, its line of pull shifts and it can actually assist extension (but that’s a minor role primarily for adductor magnus). Additionally, it can help medially rotate the thigh (especially when the hip is flexed – the adductors as a group have a secondary internal rotation component due to their attachment on the posterior femur). In summary: adducts strongly, assists in flexion and stabilizes the hip in gait by preventing excessive abduction.
Synergists
The other adductors (brevis, magnus, pectineus, gracilis) are the direct synergists for thigh adduction. Adductor longus and brevis work together for adduction and both are innervated by the anterior division of the obturator nerve. Pectineus (innervated by femoral nerve) also assists in adduction and flexion, often working with adductor longus in the early swing phase of gait to flex and adduct the thigh. During powerful adduction (e.g., riding a horse or squeezing thighs together), all adductors including longus contract in concert. For hip flexion, it synergizes with iliopsoas and rectus femoris (though those are primary hip flexors). For medial rotation, it works with the adductor magnus (anterior part) and gluteus medius/minimus (anterior fibers) when the hip is flexed.
Antagonists
The main antagonists are the hip abductors: gluteus medius and minimus, and tensor fasciae latae. These oppose the adduction that adductor longus produces. Additionally, for the flexion component, the antagonists would be the hip extensors (gluteus maximus and hamstrings). But gluteus maximus also can act as a lateral rotator and weak abductor (upper fibers), opposing the longus’s slight medial rotation and adduction. In functional terms, when standing on one leg, the abductors (medius/minimus) must counter the adduction torque of gravity – a weak adductor longus wouldn’t be noticed here because gravity does adduction; rather, a tight or overactive adductor longus can antagonize the abductors and cause a Trendelenburg-like drop of the opposite side (though true Trendelenburg is from weak abductors). Balanced force between adductors and abductors is needed for proper alignment.
Spinal Innervation
L2, L3, L4 via the obturator nerve.
Peripheral Innervation
Obturator Nerve (anterior division) innervates adductor longus. This nerve passes through the obturator canal, splits into anterior and posterior branches. The anterior branch runs between adductor longus and brevis, supplying both (and gracilis). Clinically, obturator nerve damage (as mentioned) affects adduction strength significantly, with adductor longus being one of the primary muscles lost.
Vasculature
Blood supply comes from the profunda femoris (deep femoral) artery, particularly its perforating branches, and from the obturator artery (branch of internal iliac) in the upper part. The femoral artery also gives off muscular branches to the adductors near their origin. Because the adductor longus is near the femoral triangle, it gets some supply from branches of the femoral artery (e.g., the medial circumflex femoral artery’s branch or artery of the adductors). Venous drainage goes into femoral vein via profunda femoris vein tributaries.
Clinical Relevance
Groin Strain (Adductor Strain): Adductor longus is the most commonly injured adductor in athletes (like soccer, hockey players) who do quick directional changes or kicking. A “pulled groin” often refers to a strain or partial tear of the adductor longus near its origin on the pubis. This causes pain in the groin, worse with adduction or against resistance. Severe cases can avulse a bit of bone from the pubis. Initial treatment: RICE (rest, ice, compression, elevation), followed by gentle stretching and strengthening. Chronic strains can lead to tendinopathy – “adductor tendinitis”. Physical therapy focusing on eccentric adductor strengthening and core stabilization is key for rehab.
Rider's Bones: Ossification or calcification within the adductor longus tendons can occur from chronic strain (seen historically in horse riders – from constant adductor engagement). It’s not common now, but the term “rider’s bone” refers to such calcification, usually asymptomatic, found on X-ray as a bony spur near the pubis.
Sports Hernia (Athletic Pubalgia): Adductor longus pathology often co-exists with lower abdominal wall injuries in athletic pubalgia. Because the adductor longus and the rectus abdominis insertions are close on the pubis (one on inferior pubis, one on superior), unbalanced tension (weak abdominal vs strong adductor or vice versa) can cause tears. Patients with chronic groin pain might have both an incipient hernia and adductor longus tendinopathy. Both must be addressed – sometimes surgical reinforcement of the abdominal wall and a partial adductor release are done together to relieve chronic groin pain in athletes.
Obturator Nerve Entrapment: The obturator nerve can be compressed in conditions like an obturator hernia or large pelvic masses, causing weakness of adductor longus (and other adductors) and numbness in the medial thigh. Patients might have difficulty bringing legs together and a gait that swings the leg outward (circumduction) to compensate for lack of adduction. If suspecting this, nerve conduction studies can test obturator nerve, and surgical release might be needed in case of a hernia.
Surface Anatomy: The tendon of adductor longus at the pubis can be palpated; it is prominent when the patient resists adduction with legs slightly apart. The medial border of the femoral triangle is formed by this muscle’s edge. Surgeons and clinicians use it as a guide: the femoral pulse is just lateral to it. When performing a cardiac catheterization via the femoral artery, one palpates just lateral to the adductor longus border. For femoral nerve blocks, one identifies the femoral crease and often uses the boundaries of the triangle (sartorius laterally, adductor longus medially) to locate the nerve slightly lateral to the artery.
Adductor Tenotomy: In some cases of cerebral palsy or spastic paraplegia, the adductors (especially longus) become so tight they cause “scissor gait”. An adductor longus tenotomy (surgical release of the tendon from the pubis) can improve range of motion and hygiene (ease of perineal care). The consequence is some loss of adduction power, but in non-ambulatory or minimally ambulatory patients, that is acceptable.
Bilateral Injuries: It’s worth noting adductor injuries can be bilateral, especially in sports with symmetric demands (e.g., skating). Rehabilitation must ensure balanced strength and flexibility on both sides to prevent pelvic tilt or asymmetry. Chronic unilateral adductor longus tightness can contribute to pelvic obliquity or pubic symphysis stress (leading to osteitis pubis).
Relation to Other Muscles: Adductor longus lies anterior to adductor brevis. In an obturator nerve block (for spasticity management or surgical analgesia for knee surgery), the needle is often guided between adductor longus and brevis (or brevis and magnus depending on approach) to reach the obturator nerve. Knowledge of these planes is important.
Adductor Canal: Adductor longus forms the roof of the middle part of the adductor (subsartorial) canal along with sartorius. The femoral vessels travel through this canal en route to become popliteal vessels. An adductor canal block (saphenous nerve block) is done in this region; understanding that adductor longus is more proximal and adductor magnus more distal (forming the hiatus) helps in placing the block appropriately.
