Lower Limb

Hip Joint

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The hip joint is a weight bearing synovial ball and socket joint connecting the pelvis to the leg; the head of the femur is the ball and the acetabulum the socket. It is a multi-axial joint but comparatively to the gleno-humeral joint sacrifices mobility for stability. The principal blood supply to the head of the femur is distal to proximal which is of key significance in neck of femur fracture management. 

Gross Anatomy

Articular structure

The articulating surface is the head of the femur and the acetabulum. When considering the proximal femur the head, neck and two trochanters are of structural and clinical importance. The proximal femur is roughly L shaped with the neck projecting superiomedially, this angle of inclination becomes more acute with growth until the adult angle of 115-140° is reached. 

Females have a reduced angle due to a widening of their pelvis. The femoral head makes up two thirds of a sphere and articulates with the acetabulum. It is covered in articular cartilage apart from a medially placed depression (fovea capitus) where the ligamentum teres attaches. 

The acetabulum is a hemispherical concave surface located on the lateral pelvis which articulates with the head of the femur. The acetabulum is formed by contributions of the ilium, ischium and pubis. The prominent rim of the acetabulum is approximately three quarters of a circle and is covered in articular cartilage, this is known as the lunate surface and articulates with the femur. The quarter of the circle where there is no rim is called the acetabular notch, and is bridged by the transveres acetabular ligament (continuation of the acetabular labrum). 

Centrally at the base of the acetabulum is the acetabular fossa which does not articulate with the femoral head and when soft tissues are removed is continuous with the acetabular notch. The ligamentum teres originates from the acetabular notch. The acetabulum has a substantive fibrocartilagous labrum, the acetabular labrum. This increases the articular surface area by nearly 10%(3). The result of this is that over 50% of the head of the femur fits within the acetabulum.

Cartilage: The whole of the head of the femur apart from the fovea capitus is covered in articular cartilage. The articulate surface of the acetabulum is covered in articular cartilage known as the lunate surface. Capsule: The hip joint has a two-layered capsule, an internal synovial capsule and an external fibrous capsule. The fibrous capsules proximal attachement is just on the periphery of the labrum and to the transverse acetabular ligament, distally it attaches along the intertrochanteric line on the anterior surface of the femur and posteriorly attaches proximal to the intertrochanteric crest. The fibrous capsule increases stability of the joint especially on hip extension where the tightened capsule forces the femoral head tightly into the acetabulum(3). There are three intrinsic ligaments of the joint capsule: ·      Iliofemoral: This wide shaped ligament is the strongest of the three ligaments and prevents hyperextension of the hip joint by forcing the femoral head into the acetabulum(3, 4). It is located anteriorly and superiorly. It attaches to the anterior inferior iliac spine and acetabulum rim proximally, distally it attaches to the intertrochanteric line. ·      Pubofemoral: Attaches to the obturator crest of the pubic bone proximally. It then passes inferiorly and laterally where it merges with the fibrous capsule and the medial part of the iliofemoral ligament. This ligaments function is to prevent over-abduction and to a lesser extent over-extension. ·      Ischiofemoral: This is the thinnest and the weakest of the three ligaments(3, 4). Proximally it arises on the posterior aspect from the ischial part of the acetabular ring, it then passes superiolaterally to insert on the superior aspect of the neck of femur just medial to the greater trochanter. Helps limit extension and medial rotation. Bursa: An appreciation of the bursa around the hip join is clinically useful as it can be a presentation of ‘hip pain’. There are four bursa to be aware of: ·      Trochanteric bursa ·      Iliopsoas bursa ·      Gluteus medius bursa ·      Ischiogluteal bursa Ligaments: The ligaments of the hip joint contribute to the stability of the hip. Some we have already discussed. They are as follows(4): ·      Ileofemoral: Proximal attachment anterior inferior iliac spine and acetabulum rim. Distal attachment intertrochanteric line. ·      Pubofemoral: Proximal attachment obturator crest of the pubic bone. Distally merges with the fibrous capsule and the medial part of the iliofemoral ligament. ·      Ischiofemoral: Proximal attachment ischial part of the acetabular ring. Distal attachment on the superior aspect of the neck of femur just medial to the greater trochanter. ·      Ligamentum teres of the hip joint: Proximal attachment accetabular notch. Distal attachment fovea capitus. This is intracapsular but extrasynovial. The artery of ligamentum teres runs with the ligament. ·      Transverse acetabulum: Bridges the acetabular notch connecting the inferior ends of the acetabular labrum.


The hip joint supports the weight of the body in both static and dynamic multi-axial movement. Movements at the hip are flexion, extension, abduction, adduction, medial rotation, lateral rotation and circumduction.

Blood supply

The medial and lateral femoral circumflex arteries arise from the profundus femoris in the majority of cases, which in itself is a branch of the femoral artery(5). The circumflex vessels give rise to the retinacular vessels which run proximally up the neck of femur until they reach the cartilaginous border of the head to provide the blood supply to the head. It is this distal to proximal blood flow which is of clinical significance in neck of femur fractures. The obturator artery gives rise to the vessels in the ligamentum teres, however this is of little functional significance in adults. Acetabular blood supply arises from branches of the internal iliac artery to form a circumferential blood supply to the socket. The branches of the internal iliac that make up this supply are as follows; obturator artery, superior gluteal artery and inferior gluteal artery(1,6).

Nerve Supply

Hiltons law describes innervation of a joint:


“the nerve supplying a joint supplies also the muscles which move the joint and the skin covering the articular insertion of those muscles”(7).

Innervation of the hip joint is therefore derived from the femoral, obturator, sciatic nerve, superior gluteal and nerve to the quadratus femoris(8, 9)


Derived from the mesoderm. Lower limb buds appear at 28 days gestation(1). By 7 weeks an interzone or cleft forms which will form the femoral head and the acetabulum(1, 2). At 11 weeks the head is completely encircled by acetabular cartilage and by week 16 the capsule and musculature of the joint are formed(1, 2). Postnatal further development of both the acetabulum and proximal femur depends on functional use and correct location of the femoral head. In the proximal femur this notably affects the angle of the neck. At birth the acetabulum is immature and relies on the femoral head being correctly positioned and functional within the acetabulum to develop, for example in untreated development dysplasia of the hip the acetabulum is shallow and steep(1, 2). The first 8 years are of vital importance as at this age ossification centers form in the acetabulum and further remodeling is very limited; ossification centers of the acetabulum fuse between 17 and 18 years(1).

Clinical Anatomy

Femoral neck fractures

Hip fractures represent a significant public health burden with around 70,000-75,000 cases a year with an estimated cost of  £2 billion per a year, 10% of cases die within one month and a third die within 12 months(10). This is a marker of the complex co-morbidities of these patients, thus a thorough history into the cause of the fall needs to be undertaken and all patients should be managed within a multi-disciplinary environment with orthogeriatric input.

Management is nearly exclusively surgical with NICE recommending surgery on the day or day after admission with rapid correction or control of manageable co-morbidities to facility surgery(10).

Surgical options depend on the type of fracture. Firstly one must deduce if the fracture is intra or extra-capsular. In extra-capsular fractures blood supply to the femoral head is preserved and not threatened. If the fracture is above or including the lesser trochanter extramedullary fixation such as a sliding hip screw should be used, if subtrochanteric intramedullary fixation is advisable(10).

Intracapsular fractures are more complex. Due to the blood supply, as described above, the viability of the femoral head is threatened and avascular necrosis may occur. Fixation technique decision is dependent on the degree of displacement. Displacement is judged on plain film radiographs with both AP and lateral views assessed. Gardens classification is used to classify femoral neck fractures. Non displaced fractures (Gardners I and II) undergo fixation with cancellous scews or sliding hip screw. Displaced fractures (Gardners III and IV) require arthroplasty due to disruption of the blood and high risk of avascular necrosis , this can be total hip replacement or hemiarthroplasty(10). Indications for total hip replacement are defined by NICE as the following:

·      Were able to walk independently out of doors with no more than the use of a stick and

·      Are not cognitively impaired and

·      Are medically fit for anaesthesia and the procedure

Post operatively early mobilization is the aim with multi-disciplinary rehabilitation and future falls prevention.


Pain secondary to osteoarthritis of the hip joint is present in 12% of adults of 65 years and above(11). Osteoarthritis of the hip may be primary or secondary to previous infection, injury or disease. Osteoarthritis of the hip joint has a worse prognosis than that of the hand or knee with a significant proportion requiring operative management at five years(11).

Pain is often the primary complaint, this can be felt in the anterior groin or it can be more generalized over the buttock and down to the knee. Patients may well complain that they find it hard to put on their shoes or cut their toe nails. Key signs on examination are an antalgic gait, muscle wasting, painful/reduced range of motion (internal rotation is the first effected), in later stages a fixed flexion deformity can be found(11).

Diagnosis can be made clinically, however AP plain film radiographs of the pelvis may well be useful.

Treatment should be individualized to patient factors. Education, strengthening with physiotherapy input, weight loss (if required), activity modification and assistive devices should be provided. Alongside this appropriate analgesia is needed. This should initially be paracetamol +/- non-steroidal anti-inflammatory drugs (NSAIDs). If prescribing a NSAID a proton-pump inhibitor should be co-prescribed and NSAIDs are not suitable/appropriate for all patients. Some may add weak opioids such as codeine however the evidence for this is poor(11). Intra-articular injection can also be considered; this may also provide diagnostic information.

If a patient continues to suffer from significant symptoms and pain operative intervention may be considered. Surgical options consist of arthroscopy, osteotomy, hip resurfacing and replacement(12). Patients age and degree of arthritic changes are key factors in the decision making process.

Developmental dysplasia of the hip (DDH)

DDH is a spectrum of disease ranging from mild dysplasia of the acetabulum to irreducible dislocation. 1-1.5 in 1000 live births are affected and it is more common in female patients, breech presentation and intra-uterine overcrowding(13, 14). The left hip is more commonly affected(13, 14).

In the neonate DDH is asymptomatic and therefore is screened for with Barlow and Ortolani tests. After the age of around 3 months the tissues begin to tighten and the aforementioned tests become unreliable, signs at this stage will be loss of abduction, apparent shortening of the thigh (Galeazzi sign) and asymmetrical skinfolds (however may be present in normal individuals)(13). After the child begins to walk other signs such as a trandelenburg gait and leg-length discrepancy will become apparent.

Ultrasonography prior to femoral head ossification (4-6 months) and plain film radiographs after ossification are the mainstay of investigation(13, 14).

Treatment depends on the age of diagnosis. Ultimately the aim is to maintain a reduced hip joint providing the optimal environment for normal hip development. As age at diagnosis increases this is harder to achieve, potential for hip remodeling reduces and more complex treatments are required. The following gives an overview of treatment options available according to age(13-15):

Under 6 months

·      Splintage usually with a Pavlik harness

·      Monitor with USS

6 months to 18 months

·      Closed reduction (+/- adductor tenotomy)

o   If difficulty in reduction consider arthrogram to assess if soft tissue is blocking reduction

·      If closed reduction fails open reduction

·      Reduction (closed or open) is held with a hip spica cast

18 months to 3 years

·      Open reduction (+/- osteotomy)

3 to 8 years

·      Open reduction and osteotomy

Over 8 years

·      Can be treated non-surgically or with osteotomy

·      Irrespective of above management choice must plan for a total hip replacement in adult life

Quick Anatomy

Key Facts

Development:  Derived from the mesoderm.

Blood supply: Retinacular vessels (branches of the circumflex vessels) are the predominant blood supply for the femoral head. Branches of the internal iliac artery supply the acetabulum.

Nerve supply: Innervation of the hip joint is from the femoral, obturator, sciatic nerve, superior gluteal and nerve to the quadratus femoris.


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The hip joint is a major load bearing ball and socket joint connecting the pelvis to the lower limb. The joint is very stable but retains multi-axial movement. Pathological processes can occur in all stages of life and may well require surgical intervention.


1 Weber E, Ritting A. Normal Hip Embryology and Development. In: Berry D, Lieberman J, editors. Surgery of the Hip. 1 ed: Elsvier Health Sciences; 2012. p. 200-5.

2 Wheeless C. Embryology of the Hip. In: Wheeless C, editor. Wheeless' Textbook of Orthopaedics: Duke Orthopaedics; 2013.

3 Moore KL, Dalley AF, II, Agur AMR. Clinically oriented anatomy. 5th ed. ed. Philadelphia, Pa. ; London: Lippincott Williams & Wilkins; 2006.

4 Moses K, Banks J, Nava P, Petersen D. Hip Joint. In: Moses K, Banks J, Nava P, Petersen D, editors. Atlas of clinical gross anatomy. 2nd ed. Philadelphia, PA: Elsevier/Saunders; 2013. p. 512-25.

5 Hoffmann R, Haas N. Fractures of the femoral neck (31-B).   [cited 2016 10/3/16]; Available from: https://www2.aofoundation.org/wps/portal/!ut/p/a0/04_Sj9CPykssy0xPLMnMz0vMAfGjzOKN_A0M3D2DDbz9_UMMDRyDXQ3dw9wMDAx8jfULsh0VAdAsNSU!/?bone=Femur&segment=Proximal&soloState=lyteframe&contentUrl=srg/popup/further_reading/PFxM2/31/661_31_fem_neck_fxs_gen_consid.jsp

6 Itokazu M, Takahashi K, Matsunaga T, et al. A study of the arterial supply of the human acetabulum using a corrosion casting method. Clin Anat. 1997;10(2):77-81.

7 Hilton law.  Farlex Partner Medical Dictionary; 2012.

8 Birnbaum K, Prescher A, Hessler S, Heller KD. The sensory innervation of the hip joint--an anatomical study. Surg Radiol Anat. 1997;19(6):371-5.

9 Cheatham SW, Kolber MJ. Orthopedic management of the hip and pelvis. St. Louis, Missouri: Elsevier, Inc.; 2016.

10 NICE. Hip fracture: management. National Institute for Health and Excellence Guidance. 2011 22/06/11.

11 NICE. Osteoarthritis. Clinical Knowledge Summaries. 2015.

12 Gandhi R, Perruccio AV, Mahomed NN. Surgical management of hip osteoarthritis. CMAJ. 2014 Mar 18;186(5):347-55.

13 Sankar W, Horn D, Wells L, Dormans J. The Hip. In: Kliegman R, Behrman RE, Nelson WE, editors. Nelson textbook of pediatrics. Edition 20 ed. Phialdelphia, PA: Elsevier; 2016. p. 3274-83.

14 Schmitz M, Rush J, Milbrandt T. Pediatric Orthopaedics.  Miller's review of orthopaedics. Seventh edition. ed. Philadelphia, PA: Elsevier; 2016. p. 264-334.

15 Chalmers CR, Smith CP. MRCS A essential revision notes. Knutsford: PasTest; 2012.