Adductor Magnus Anatomy

The adductor magnus is the largest muscle of the adductor compartment and one of the largest muscles in the body. It is a triangular fan whose apex is at the pubis and ischium and whose base sweeps almost the entire length of the medial femur, from the gluteal tuberosity proximally to the adductor tubercle distally.

Two muscles in one. It is best understood not as one muscle but as two, and this is the point examiners return to. The anterior, more horizontally orientated adductor (pubofemoral) part arises from the pubic and ischial rami and inserts into the linea aspera; the posterior, vertically orientated hamstring (ischiocondylar) part arises from the ischial tuberosity and inserts by a rounded tendon on the adductor tubercle. The two differ in origin, orientation, action, innervation and embryological derivation, so the muscle is a hybrid of the adductor and hamstring groups, and the adductor hiatus sits in the aponeurosis where the two parts meet.

Why there are two. The ischiocondylar part shares its ischial tuberosity origin and its innervation with the hamstrings and derives from the same flexor (posterior) muscle mass; the adductor part derives from the adductor (medial) mass. The muscle is a fusion of two developmental units, which is why one half of it is supplied exactly like the true hamstrings.

Origin. The adductor part arises from a small area on the inferior (ischiopubic) ramus of the pubis and the ramus of the ischium, deep to the origins of adductor brevis and gracilis. The hamstring part arises from the inferolateral aspect of the ischial tuberosity, immediately adjacent to and partly blended with the origins of the semimembranosus and the conjoint tendon of biceps femoris and semitendinosus.

Why the ischial origin matters. Because the ischiocondylar origin blends with the hamstring origins, the adductor magnus is involved in proximal hamstring pathology: an ischial tuberosity avulsion or apophyseal injury frequently involves it, and in any posterior approach to the ischium its origin is encountered alongside the hamstring origins and must be recognised.

Insertion. A continuous sweep down the medial femur:

• Gluteal tuberosity, the rough area on the posterior proximal femur medial to the vastus lateralis origin, and a landmark in posterior proximal femoral exposure
• The entire length of the medial lip of the linea aspera
• Medial supracondylar line
• A rounded tendon onto the adductor tubercle, the distal ischiocondylar portion

This is the longest femoral insertion of any muscle, spanning almost the whole shaft.

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Two nerves, two parts. The adductor part is supplied by the posterior division of the obturator nerve, root values L2, L3, L4. The hamstring part is supplied by the tibial division of the sciatic nerve, root values commonly given as L4, L5, S1, the same territory that supplies the true hamstrings. Adductor magnus is, with the pectineus, one of the two dually innervated muscles of the adductor group, and its dual supply comes from two different nerves entirely.

The obturator nerve. It arises from the anterior divisions of the ventral rami of L2-L4, descends on the medial border of the psoas, crosses the pelvic brim behind the common iliac vessels, runs along the lateral pelvic wall above the obturator vessels, and exits through the obturator canal approximately 2-3 cm inferolateral to the pubic tubercle. Its divisions are separated by the obturator externus in the pelvis and canal, and by the adductor brevis in the thigh, so the posterior division lies posterior to the adductor brevis on the anterior surface of the adductor magnus.

What the posterior division supplies. The adductor part of adductor magnus, the obturator externus and variably the adductor brevis, and an articular branch to the knee that descends through the adductor hiatus with the popliteal artery to the posterior capsule. That knee branch is the anatomical basis of referred medial knee pain in hip pathology, and the reason a child with a slipped upper femoral epiphysis, Perthes disease or a septic hip presents complaining of the knee. Never accept medial knee pain at face value in a child.

The sciatic branch. The branch to the ischiocondylar part arises from the tibial division of the sciatic nerve in the posterior thigh, alongside the branches to semimembranosus, semitendinosus and the long head of biceps femoris, and enters the posterior surface of the ischiocondylar portion.

Why adduction survives an obturator lesion. A complete obturator nerve lesion denervates adductor longus, brevis, gracilis and the adductor part of magnus, but the ischiocondylar part retains its sciatic supply and the pectineus retains its femoral branch. Adduction is therefore weakened, not abolished, which is the answer examiners want. An obturator nerve block or neurectomy cannot abolish adduction for the same reason: state this explicitly when consenting for neurectomy, and to the urologist or anaesthetist relying on a block to abolish the adductor jerk during transurethral bladder resection, where a residual adductor twitch may persist despite an apparently successful block.

The MRI denervation pattern. In an obturator lesion, oedema and later fatty atrophy affect adductor longus, brevis, gracilis and the adductor part of magnus, with relative sparing of the ischiocondylar part and of the pectineus. In a tibial division sciatic lesion the pattern for adductor magnus is the reverse, alongside the true hamstrings. The selective pattern is a reliable localiser of an obturator lesion and should prompt a search for a pelvic cause.

Localising a lesion by root value. Hip adduction is L2/L3/L4 (obturator) with an L4/L5/S1 (sciatic) contribution through the ischiocondylar part; hip extension is L5/S1 predominantly (gluteus maximus, hamstrings, ischiocondylar adductor magnus); distal medial thigh sensation is the obturator cutaneous branch, from the anterior division. Weak adduction with a medial thigh sensory patch localises to the obturator nerve; add quadriceps weakness and the lesion is proximal, in the lumbar plexus, the L2-L4 roots, or a retroperitoneal haematoma, abscess or tumour.

The other dually innervated muscles. Pair adductor magnus with the pectineus (obturator anterior division plus femoral), the biceps femoris (long head tibial division, short head common peroneal division) and, in the upper limb, flexor digitorum profundus (median and ulnar).

Sources. The profunda femoris dominates; the others contribute near the origin, the ischial tuberosity and the hiatus.

• Profunda femoris artery: muscular branches, the dominant supply
• Perforating branches of the profunda femoris: typically three to four, which pierce the adductor magnus on their way from the anterior to the posterior compartment, supply the muscle and give nutrient branches to the femur
• Obturator artery, posterior branch: the proximal muscle near its pubic and ischial origin
• Medial circumflex femoral artery: proximal supply, and the vessel of concern in the medial approach to the hip
• Inferior gluteal artery: the ischiocondylar part near the ischial tuberosity, alongside the hamstring origins
• Femoral artery and, distally, the descending genicular artery: near the hiatus and the adductor tubercle

The perforators. Because they pass through the muscle to reach the posterior compartment, dividing the adductor magnus blindly bleeds from a vessel that then retracts into muscle, or into the posterior compartment where the sciatic nerve lies.

The descending genicular artery. It arises from the femoral artery within the adductor canal, just proximal to the adductor hiatus, and gives muscular, saphenous and articular branches. It is the pedicle of the medial femoral condyle vascularised corticoperiosteal flap, so in a subvastus exposure it is identified and ligated deliberately, and preserved if such a flap may be needed.

Anterior. Adductor brevis proximally and adductor longus distally; the posterior division of the obturator nerve on its anterior surface; the profunda femoris artery and vein with their perforating branches, which pierce the muscle; and distally the adductor canal contents against its posteromedial surface, where the muscle forms the distal posteromedial wall of the canal.

Posterior. The true hamstrings, semimembranosus, semitendinosus and biceps femoris, and the sciatic nerve in the posterior compartment. The muscle forms the anterior wall of the posterior compartment and the floor on which the hamstrings and the sciatic nerve lie.

Medial and distal. Medially the gracilis, the most medial strap and the only biarticular adductor, and the great saphenous vein in the subcutaneous plane. Distally the adductor tubercle, with the MPFL femoral origin between it and the medial epicondyle; the medial epicondyle and superficial MCL origin distal and anterior; the medial head of gastrocnemius arising just posterior to the adductor tubercle region; and the popliteal fossa contents beyond the hiatus.

The adductor canal. It runs from the apex of the femoral triangle, where the medial border of sartorius crosses the medial border of adductor longus, to the adductor hiatus, which is its distal boundary.

• Anterolateral wall: vastus medialis
• Posteromedial wall: adductor longus proximally, adductor magnus distally
• Roof: the vastoadductor membrane, deep to the sartorius
• Contents: femoral artery, femoral vein, saphenous nerve, nerve to vastus medialis, and the descending genicular artery arising within it

The hamstring that does not cross the knee. The ischiocondylar part has a vertical line of pull from the ischial tuberosity to the adductor tubercle, which is a hip extension vector, and it shares its origin, its innervation and its embryological derivation with the true hamstrings. It extends the hip but has no attachment below the knee, and so has no knee flexion action.

Be precise about magnitude. In vivo measurement of hip extensor moment arms found that in the anatomical position the adductor magnus moment arm averaged about 15 mm, against roughly 61 mm for the hamstrings and 79 mm for the gluteus maximus. Its moment arm then increased with hip flexion up to about 75 degrees before declining, whereas the gluteus maximus moment arm decreased as the hip flexed and the hamstrings peaked at around 35 degrees.

The clinical corollary. The adductor magnus contributes relatively more to hip extension out of a flexed hip, in the drive phase of a deep squat, rising from a low seat or accelerating from a crouched start, precisely where the gluteus maximus is at its mechanical worst. Combined with its large cross-sectional area, that makes it functionally relevant in exactly those tasks. Do not overstate it as the second or third strongest hip extensor in the anatomical position; its advantage is positional.

Architecture and moment arms. The muscle is fan-shaped and multipennate, and its portions have different moment arms: the more horizontal proximal fibres favour adduction, the vertical distal fibres favour extension. The adduction moment arm increases with hip abduction, which is why the muscle is loaded eccentrically at the extremes of abduction in change-of-direction sport.

Gait. The adductor group is active in loading response and pre-swing, contributing to pelvic stabilisation and to the stance-to-swing transition. The ischiocondylar part is additionally active in terminal swing and early stance, working with the hamstrings to decelerate the limb and extend the hip.

Synergists and antagonists.

• Adduction synergists: adductor longus and brevis, pectineus, gracilis, inferior gluteus maximus fibres, quadratus femoris
• Hip extension synergists: gluteus maximus, semimembranosus, semitendinosus, long head of biceps femoris
• Antagonists: gluteus medius and minimus and tensor fascia lata (abduction); iliopsoas, rectus femoris and sartorius (flexion)

Finding the adductor tubercle. Palpate the medial epicondyle, then move proximally and slightly posteriorly to the small prominence at the distal end of the medial supracondylar line, where the rounded adductor magnus tendon inserts. It is best appreciated with the knee slightly flexed and the muscle relaxed. The tendon itself is palpable as a firm cord running to the tubercle in the distal medial thigh, particularly with resisted hip extension in slight abduction.

The rest of the muscle. The bulk is the deep posteromedial mass of the thigh, palpable between the hamstrings posteriorly and the adductor longus and gracilis anteriorly and medially. The ischial tuberosity is palpable with the hip flexed, and the ischiocondylar origin blends with the hamstring origins there. The adductor hiatus is not directly palpable, but its level should be known.

Measuring abduction. Always square the pelvis before measuring abduction, and test with the knee both flexed and extended.

Imaging. MRI distinguishes an adductor magnus strain from a hamstring or adductor longus injury, and the selective denervation pattern, adductor part against ischiocondylar part, localises an obturator versus a tibial division sciatic lesion. CT angiography is the investigation of choice for suspected arterial injury at the hiatus. Radiographs of the pelvis in an adolescent with posterior thigh pain exclude an ischial tuberosity apophyseal avulsion, which involves the blended hamstring and adductor magnus origin.

The anatomy. The adductor hiatus is an opening (an osseoaponeurotic hiatus) in the aponeurotic distal insertion of the adductor magnus, between the insertion into the medial supracondylar line and the rounded tendon to the adductor tubercle, at roughly the junction of the middle and distal thirds of the thigh on the posteromedial aspect. The femoral artery and vein pass through it from the anterior compartment to the popliteal fossa and become, by definition, the popliteal artery and vein; the articular branch of the posterior division of the obturator nerve passes through with the artery to the knee. The descending genicular artery arises just proximal to it.

Why the artery is vulnerable. The vessel is relatively tethered at the hiatus by its aponeurotic margins, and tethered again distally by the fibrous arch of the soleus. Between these two fixed points the popliteal artery has limited capacity to accommodate displacement, so in knee dislocation and in displaced distal femoral and proximal tibial fractures it is stretched or torn between two tethered points. Injury ranges from an intimal tear with delayed thrombosis to complete disruption, and a palpable pulse does not exclude an intimal injury: that is the clinical trap.

The protocol for a knee dislocation. Any knee dislocation or grossly displaced distal femoral fracture mandates a documented vascular assessment, and delay to diagnosis and revascularisation markedly increases the amputation rate, which is what makes the assessment time-critical.

1. Reduce urgently and immobilise in about 20-30 degrees of flexion
2. Document a full vascular examination before and after reduction: pulses, capillary refill, colour, temperature, and a Doppler ankle-brachial pressure index (ABPI)
3. ABPI of 0.9 or greater with a normal examination: serial documented examinations for at least 24-48 hours, because thrombosis can be delayed. Prospective data support a selective rather than a routine arteriography policy on this basis
4. ABPI less than 0.9, an abnormal examination, or an expanding haematoma or bruit: urgent CT angiography or on-table angiography and vascular surgical involvement. Hard signs of ischaemia mandate immediate exploration without waiting for imaging
5. Examine the common peroneal nerve, injured in a substantial proportion of knee dislocations, and anticipate compartment syndrome after revascularisation

Three landmarks a few millimetres apart. The medial distal femur has three closely spaced landmarks that are routinely confused, and getting them right is what separates an accurate MPFL reconstruction from a stiff or unstable knee.

1. Adductor tubercle: the rounded tendinous insertion of the adductor magnus at the distal end of the medial supracondylar line, proximal and slightly posterior to the medial epicondyle
2. Medial epicondyle: distal and anterior to the tubercle; the origin of the superficial medial collateral ligament
3. MPFL femoral origin: between the adductor tubercle and the medial epicondyle, slightly distal and anterior to the tubercle (the quantitative cadaveric mapping places it 1.9 mm anterior and 3.8 mm distal)

Why the tendon is the practical landmark. The tubercle can be difficult to identify by palpation alone in a thick knee, but the adductor magnus tendon is a firm, easily traced cord leading directly to it. Following the tendon distally reliably finds the tubercle, and from there the MPFL origin. Quantitative cadaveric mapping of the medial knee has described the MPFL femoral attachment in relation to the adductor tubercle and the medial epicondyle, and has defined the superficial MCL femoral attachment as a distinct site lying distal and anterior to the adductor tubercle.

Then confirm it on the screen. Fluoroscopic confirmation on a true lateral, using a radiographic point localised in relation to the posterior cortical extension line and the level of the posterior origin of the medial femoral condyle, has been proposed as more reliable than palpation of the bony landmarks alone. Femoral tunnel malposition is a well-recognised technical error in MPFL reconstruction, and the table gives what each error costs.

The tendon as a construct. Adductor magnus tendon sling techniques leave the distal tendon attached to the adductor tubercle and use it as a pulley or fixation point for a gracilis or semitendinosus graft, or as the graft itself, which avoids drilling a femoral tunnel altogether. That is particularly attractive in children, where a femoral tunnel adjacent to the distal femoral physis risks growth disturbance; physeal-sparing techniques built around the adductor magnus tendon are a recognised option for paediatric patellar instability. In posterior cruciate and multiligament surgery the tendon and the tubercle also serve as reference points for medial-side reconstruction tunnels.

Adductor magnus strain. The mechanism is high-velocity eccentric loading during sprint acceleration, hurdling or a change of direction, with the hip abducted and extending. It presents as deep posteromedial thigh pain, often described by the athlete as neither a hamstring nor a groin injury, with impaired acceleration as the functional hallmark, because the ischiocondylar part is a hip extensor whose moment arm is greatest with the hip flexed. It is frequently mislabelled as a hamstring strain, because of the posterior location and the ischial origin, or as an adductor strain, because of the medial location; MRI localises it precisely.

Rehabilitation. Criteria-based, as for other muscle injuries, with a deliberate emphasis on hip extension and eccentric adduction loading rather than knee flexion work, because the muscle does not cross the knee. Return to play requires:

• Pain-free full range and no tenderness
• Pain-free maximal resisted adduction and resisted hip extension
• Restored strength on dynamometry
• A completed sport-specific progression through acceleration and change of direction before match play

Ischial tuberosity avulsion. In the adolescent athlete an ischial apophyseal avulsion is managed almost always non-operatively, with radiographs mandatory to make the diagnosis. In the adult a proximal hamstring avulsion involves the same blended origin, and the extent of tendon involvement determines whether surgical repair is offered.

Obturator neuropathy. The causes are pelvic and acetabular surgery, pelvic fracture, obstetric compression, gynaecological and urological surgery, tumour or lymphadenopathy, pelvic haematoma, obturator hernia, and in athletes fascial entrapment at the exit from the obturator canal over the short adductor. Investigate with MRI of the pelvis to exclude a mass or hernia, electromyography of the adductors, ideally after exercise provocation, and a diagnostic obturator nerve block.

Adductor compartment syndrome. Rare but recognised, most often after crush injury, a large adductor haematoma (particularly with anticoagulation), reperfusion, or prolonged compression. It presents with a tense tender medial thigh, pain out of proportion, and pain on passive hip abduction, which stretches the adductors. Treatment is a medial thigh fasciotomy through a longitudinal medial incision, combined with a lateral incision when the anterior compartment also requires decompression.

Contracture. Adductor contracture gives fixed adduction with reduced abduction, apparent limb shortening, and difficulty with hygiene and positioning. In spastic hip disease the magnus is a deep contributor but is rarely released.

The release sequence. In an adductor release for spastic hip displacement the sequence is adductor longus, then gracilis, then adductor brevis (partial), then pectineus if abduction remains restricted, to a target of approximately 40-45 degrees of abduction per side. The adductor magnus is rarely released, for three anatomical reasons:

1. The perforating branches of the profunda femoris pass through it, so blind division bleeds
2. The sciatic nerve and the true hamstrings lie immediately behind it in the posterior compartment
3. Its ischiocondylar part is a hip extensor whose loss would compromise standing and transfers in a child whose extension power is already limited

Where a deeper release is genuinely required it is performed under direct vision with deliberate control of perforators, addressing only the anterior adductor portion. Avoid a complete anterior branch obturator neurectomy: it risks an abduction contracture, and adduction cannot be abolished anyway.

Selection matters more than technique. Age at surgery and the preoperative migration percentage are the variables most often quoted as selection criteria, alongside the degree of acetabular deficiency, but in the long-term series cited in the evidence base neither age at surgery nor preoperative migration percentage significantly affected outcome; the ability to walk preoperatively and a spastic diplegic pattern predicted success, and the migration percentage at one year after surgery was the strongest predictor of the final result. A proportion of hips displace further despite release and require later reconstruction.

The medial (Ludloff) approach. The original Ludloff interval passed between adductor brevis and adductor magnus, behind the brevis and in front of the magnus, which is where the posterior division of the obturator nerve lies and which brings the surgeon closer to the medial circumflex femoral artery, lying proximally deep to pectineus and adductor brevis. The Ferguson modification works anterior to the adductor brevis, avoiding both, and is the safer plane; limit posterior dissection.

What is released and what follows. The blocks to reduction are the iliopsoas tendon at the lesser trochanter, the ligamentum teres, the pulvinar and the transverse acetabular ligament. Capsulorrhaphy is not possible, residual dysplasia is common, and avascular necrosis is the feared complication; immobilise in the human position, roughly 100 degrees of flexion and 45-55 degrees of abduction.

At every level. Because the insertion runs the whole length of the medial lip of the linea aspera, the muscle is encountered at every level of a medial or posteromedial femoral exposure. The rule is the same at each: the perforating branches of the profunda femoris pass through the muscle and the sciatic nerve lies immediately behind it, so divide it only under direct vision, control perforators deliberately, never chase a retracted vessel posteriorly, and never dissect blindly behind it; pack and gain vision instead.

Distally. At and beyond the adductor hiatus the popliteal vessels lie immediately deep to the muscle, which is why retractors here must be seated on bone and placed under vision, and why flexing the knee relaxes the vessels. The medial approach to the distal femur uses the interval between the vastus medialis anteriorly and the adductor magnus posteriorly, with the adductor magnus tendon as the posterior landmark and the vessels at the hiatus as the posterior danger.

Two operations in that field. For a medial closing-wedge or opening-wedge distal femoral osteotomy the adductor tubercle and the adductor magnus insertion mark the proximal extent, and the muscle must be elevated to expose the medial cortex. The medial femoral condyle vascularised corticoperiosteal flap is raised on the descending genicular artery in the field that the adductor magnus and its tendon define.

Variation and prevalence

• The degree of separation between the adductor and ischiocondylar parts varies: in some individuals the two are clearly distinct with a definable fascial plane, in others they merge gradually. The innervation split is consistent, which is why it is a more reliable teaching point than the morphology.
• The size and shape of the adductor hiatus vary, as does the exact level at which it lies. The clinical point — that the vessel is tethered there — is invariant.
• The reported prevalence of popliteal artery injury in knee dislocation varies widely between series depending on case mix, energy of injury and whether low-energy dislocations are included. The consistent finding across series is that delay to revascularisation, not the reported incidence, determines the amputation rate.

Differences in described technique and guidance

Registry and outcome signals

• National trauma registries and audit programmes capture amputation and revascularisation after knee dislocation and displaced periarticular fracture; the consistent signal is that time to revascularisation is the dominant modifiable determinant of limb salvage, which is the basis for a mandatory documented vascular assessment.
• Patellofemoral instability cohorts consistently show lower recurrence after MPFL reconstruction than after isolated soft-tissue medial reefing, and identify femoral tunnel malposition as a leading cause of failure — reinforcing the importance of the adductor tubercle landmark and of radiographic confirmation.
• Hip surveillance programmes for cerebral palsy have reduced dislocation rates where implemented systematically, and the standard release sequence deliberately spares the adductor magnus.

High- versus limited-resource practice

• Well-resourced settings: bedside Doppler ABPI, immediate CT angiography, on-table angiography, vascular surgical cover, intraoperative fluoroscopy for the MPFL femoral point, MRI for muscle injury localisation and denervation pattern, and physeal-sparing MPFL techniques with modern fixation.
• Limited-resource settings: the assessment that matters most is nearly free — repeated documented clinical examination of the reduced knee, and a handheld Doppler for an ABPI, which is inexpensive and decisive. Where angiography is unavailable, hard signs of ischaemia mandate exploration, and the surgeon should be prepared to expose the popliteal artery through a posteromedial approach with the adductor magnus and the hiatus as the proximal landmark. MPFL reconstruction using the adductor magnus tendon as a pulley or anchor is attractive where implants are scarce and in children, because it needs no femoral tunnel and no interference fixation.
• Universal principles: state the dual innervation and what it explains; measure and document an ABPI in every knee dislocation, because an intimal flap can preserve a palpable pulse and declare itself later; trace the adductor magnus tendon to the adductor tubercle and confirm the MPFL origin radiographically; divide the adductor magnus only under direct vision because the perforators pass through it and the sciatic nerve lies behind it; and spare the muscle in adductor release because it is a hip extensor.

Related pages: Knee Dislocation Management is where the adductor hiatus stops being anatomy and becomes an emergency, and Vascular Injury in Fracture-Dislocation covers the assessment pathway in full. MPFL Injury and Patellofemoral Instability are where the adductor tubercle earns its keep as the landmark for the femoral origin, and where the adductor magnus tendon is itself used as a pulley or anchor. Adductor Longus, Adductor Brevis, Gracilis and Pectineus complete the medial compartment, with adductor magnus the deepest and the only one to cross into the hamstring group. Obturator Nerve Anatomy supplies the adductor part while the tibial division of the sciatic supplies the ischiocondylar part - the dual innervation this page turns on. Hamstring Injuries and Proximal Hamstring Avulsion share the ischial tuberosity origin and the sprint-acceleration mechanism. Popliteal Artery Entrapment Syndrome is the chronic counterpart of the same tethering problem at the other end of the vessel's course.