Hip joint is a strong and stable multiaxial synovial joint of ball and socket type. femoral head is the ball and the acetabulum is the socket . Next to the shoulder joint , it is the most movable of all joints.

Articular surface of the hip joint
The round head of femur articulates with the cup like acetabulum of the hip joint.
Acetaabulum The acetabilar articlular surface is an incomplete ring ,the lunate surface . Acetabular depth is incersed by a fibrocartilaginous acetabular labrum , which bridges the acetabular notch via the tranverse acetabular ligment . Acetabular fossa contains fibroelastic fat coverd by Synovial membrane.

Articular capsule The strong , loose fibrous capsule permit the free movement of the hip joint
It attaches proximally to the acetabulum and transverse acetabular ligment . It surrounds the femoral neck and is attached in front toto the intertrochanteric line , behind about 1cm above the intertrochanteric crest. Most capsular fibres take a spiral course from the bone to the intertrochanteric line, but some deep fibers pass circularly around the neckn forming the orbicular Zone. These fibres from a collar around the neck that constrict the capsule and helps to hold the femoral head in the acetabulum. Some deep longitudinal fibres of the capsule from refinacula, Which reflect superiorly along the fermoral neck as longitudinal bands that blend with the periosteum. Retinacula contains retinacular blood vessels, branches of the medial and a few from lateral femoral circumflex that supply the head and neck of the femur. Thick parts of fibrous capsule from the ligament of the hip joints , which pass in a spiral fashion from the pelvis to the fenur . They allow considerable flexion of the hipjoint, but restrict extension of the joint to 10o to 20o beyond the vertical position .

Ligaments of hipjoint
1. Illiofemoral ligament 2. Ischiofemoral ligament
3. Pubofemoral ligament] 4. Ligament of the head of the femur

1. Illiofemoral
Fibrous capsule is reinforced anteriorly by the ‘Y’ shaped strong ligament the illiofemoral proximally it is attached to the anterior inferior illiac spine and acetabular rim and distally to the intertrochanteric line of the femur .
Function :- This will prevent the hyperextension of the hip joint during standing.
2) Pubofermoral
Fibrous capsule is reinforced inferiorly and anteriorly by this ligament. It is a weak ligament. It arises from the pubic part of the acetabular rim and the iliopubic eminence and blends with the medial part of the ilioemoral ligament .
Function:- This ligment tightens during extension and becomes lense during abduction. It tends to prevent overabduction of the thigh.
3) Ischiofermoral
This will reinforce the fibrous capsule posteriorly . It arises from the ishial portion of the actabular rim and spirals superolaterally to the neck of the femur medial to the base of the greater trochanter.
Fuction : This will screw the fermoral head medially into the actabulum during extension of the thing at the hipjoint, there by resisting hyperextension of it .
4) The ligament of the head of femur (Ligamnetum teres femoris )
It is a weak joint. It’s wide end is attached to the margins of the acetabular and to the traverse acetabular ligament and its narrow end is attached to the fovea of the femur . Usually it contains a small artery to the femur and which is abranch of the obturator artery.
Fuction : Ligament of head is stretched when the flexed thigh is addvacted or laterally rotated .
Clinical significance Fractures of the femoral neck close to the head often disrupt the blood supply to the head of the femur . In some cases the blood supplied via the artery inthe ligament of the head may be the only bloood recieved by the proximal fragment of the femoral head . If this ligment is ruptured, the fragment may undergo asceptic necrosis.

The synovial capsual of the hipjoint
It lines the internal surface of the fibrous capsule, the acetabular fossa and covers the fatty pad in tne acetabular noch. It is attched to the edges of the acetabular fossa and to the transverse acetabular ligament . The synovial capsule protrudes inferior to the fibrous capusle posteriorly , where it forms a bursa which protect the tendon of the obturator extenus muscle.

Movement of the hipjoint
1 Flexion
2 Extension
3 Abduction
Flexors Strongest flexors are iliopsoas muscle (illiacus and pesoas major )
Extensors Chif extensors are gluteus maximus and hamstring muscle (Gluteus maximus is relatively inactive unless forceful extension is requried)
Abductors Gluteus Medius and Gluteus Minimus
Adductors Adductor muscles -Adductor Longus
-Adductor brevis
-Adductor Magnus
Medical rotators Tensor fascia latae, Gluteus Medius, Gluteus Minimus
Lateral rotators Obuturator muscvles, gemelli and Quadratus femoris Lateral rotation is usdally limited by the tension of medial rotators and iliofemoral ligament .
Stablity Hip joint is very strong and stable joint surrounded by powerful muscles and dense fibrous capsule, strengthened by strong intrinsic ligments particularly iliogemoral ligament.

BLOOD SUPPLY
Mainly by -Medial and lateral cicumflex femoral arteries
-Deep division of the superior gluteal artery
-Inferior gluteal artery
Head of the femur is supply by - Posterior division of the obturator artery
Nerve Supply Femoral nerve - Via nerve to the rectus femoris muscle
Obturator nerve - Via it’s anterior division.
Sciatic nerve:- - Via the nerve to the quadratus femoris muscle
Superior gluteal nerve - Here the femoral, sciatic and oburator nerves also supply the knee joint, so hip disease may cause a refered pain to the hipjoint.

Dislocation of hip joint
It can be of two types
1 Congenital dislocation
2 Aquaired dislocation

According to the direction of dislocation
1 Posterior dislocation - Commonest
2 Anterior dislocation
3 Central dislocation

Congenital dislocation : This Condition is more Common in girls , than boys (Ration is 7:1 . This is more Commonly Seen in European countries and in Japan. It is bilateral in about half the cases. Left hip is more commonly affected than the right hip
Aetiology and pathogenesis
1) Genetic - It tends to run in familes There are two heritable fectures which could predispose to hip instability are Generalised joint laxity :- Which is a dominant trait
Acetabular displasia.
2) Hormonal factors - High levels of maternal oestrogen, progesterone and relaxin in the last
months of pregnancy-may aggravate the ligamentous laxity in the infant
3) Intrauterine malpostion - Breech presentation with extended legs may be the cause
Clinical features -
Congenital dislocation is not obvious at birth . The characteristic clinical sign is the inability to abduct the thigh. In addition the affected limb seems to the shorter in unilateral dislocation , because the dislocated femoral head is more superior than on the normal side In bilateral dislocation there is an abnormally wide perineal gap Abduction is decreased.
Diagnosis
Can be confirmed by ultrasonography . At birth the acetabulum and femoral head are eatilagenous and therefore it is invisible on plane x-rays. They are helpful after 6 months. 80-90 or of unstable hips at birth will stabilize spontaneously in 2-3 weeks.

AQUIRED DISLOCATION
Dislocation occuring after the 1st year of life is usally due to one of the 3 cause -
-Pyogenic arthritis.
-Muscle imbalance
-Trauma
Rare causes are
-Tuberculesis
-Charcot’s disease.

Dislocation following sepsis
In infants - the femour may be infected via the umnilicus or via the femoral vein puncture. Infection readly affected the femoral head and the joint .
In Older children Acute osteomyelitis the metaphysis may be the cause . Here the head of the femur may be destroyed and pathological dislocation result. On X-ray femoral head appears to be completely absent.

Dislocation due to muscle imbalance
Here the hip adductors become weaker than adductors due to unbalanced parplysis in childhood . This is seen in - Cerebral
- Myelomeningocele
- After poliomylitis etc.
The greater trochanter fails to fails to develop properly, the femoral neck become valgus and hip may subluxate or dislocate.

Traumatic dislocation
This is very uncomon because this articulation is very strong and state.
-Posterior - Anterior - Central
Posterior dislocation:- Most common varity. usually occurs in a road accident, when someone is seated in a trunk or car is thrown forward & striking against the dashboard. Here the femur is thrust upwards and femoral head is forced out of it’s socket.
Here the leg is short and lies adducted, internally rorated and slightly flexed. In this postion the femoral head is covered posteriorly by capsule rather than bone . As a result the capsule ruptures inferiorly and posteriorly allowing the fermoral head to pass through the tear in the capsule and over the posterior margin of the acetabulum. Often the acetabular margin fractures,producing a fracture-dislocation of the hipjoint when the femoral head dislocates it usually carries the acetabular bone fragment and tne acetabular labrum with it .

Diagnosis Is by x-ray AP view . femoral head is seen out of it’s socket and above the acetabulum.
Complication
Early.
Sciatic nerve injury
Since sciatic nerve is lying close to the hipjoint , it may be injured during posterior dislocations. this result in paralysis of the hamstring muscles and of the muscles distal to the knee suppied by the sciatic nerve . There will be sensory changes in the skin over the posterior and lateral aspects of the leg and over much of the foot.
Vascular injury- Occasionally the superior gluteal artery is torn and there will be profuse bleeding The torn vessel need to be ligated.
Late
Avascular necrosis- The blood supply of the femoral head is seriously impaired in at least 10% of traumatic hip dislocations. On X-ray it can be seen as increased density of the femoral head ,but this is not least for six week and sometimes very much longer.
Myositiis ossificans Uncommon complication . It is related to the severity of the injury . In such conditions period of best should be prolonged.
Osteoarthitis
due to  1. Cartilage damage of the time of dislocation
           2 .the presence of retained fragment in the joint
or 3) Ischaemic necrosis of the femoral head .

ANTERIOR DISLOCATION
Rare Usual cause is a road accident or air crash .Dislocation of one or even both hips may occur when a weight falls on to the back of a person , with his legs wide apart , knees straight and back bent forwards. Here the leg lies externally rotated , abducted and slightly flexed. It is not short because the attachment of rectus femoris prevent the head from dislocation upwards. The prominent head is easy to feel.
X-ray In AP view the dislocation is usally obivious, and lateral view confirm the diagnosis.
Complication Avascular necrosis is the only complication.

CENTRAL DISLOCATION
A fall on the side or a blow over the greater trochanter may thrust the femoral head into the floor of the acetabulum and fracture of the plevis. In this case trochanter and hip region are tender. Little movements are possible. Patient should be carefully examined for pelvic and abdominal injuries.
On X-ray The femoral head is displaced medically and the acetabular floor is fractured.
Complication
Early
Visceral injury.
Shock will be severe in such cases.
Late
Joint stiffness with or without osteoarthritis.
Other conditions affecting hip joint

Femoral neck fracture
Usually seen in elderly woman. Main reason is the osteoporosis of bone. A common injury is a fall on the greater trachanter. The lateral rotation and Shortening of limb are characteristic clinical features. The rotation results from the change in the axis of the limb owing to the separation of the body and head of the femur. A variable amount of blood may reach the femoral head through a branch of the obturator artery that runs in a ligament of the head of the head. During this fracture, the ligament of the head of the femur may be ruptured sometimes other blood vessels supplying the femoral head are torn when the femoral neck fractures. Generally the more proximal the fracture, the greater are the chances of interrupling the vascular supply. A poor blood supply may results in non-union and avascular necrosis of the femoral head. Intracapsular fractures almost always present healing problems because they usually interfere with the blood supply to the proximal bone fragment
2. Perthes disease
The boys between the age 5-10 years are commonly affected. It is due to the deficient blood supply to the head of the femur, which undergoes aseptic necrasis resulting in collapse.
3. Slipped epiphysis (adolescent coxa vara)
This is an affection of late childhood in which the upper femoral epiphysis is displaced from its normal position upon the femoral neck. The condition is often associated with over weight from endocrine dysfunction, but in other cases the patient is of normal child.
4. Tuberculosis of hip
The hip is one of the joints most frequently affected by tuberculosis. The patient may have a history of active pulmonary tuberculosis.
5. Acute Suppurative arthritis
This condition is more common in children. It is often secondary to osteomyelitis of the upper end of femor.
6. Rheumatoid arthritis
Hip joint is not affected usually in case of RA. But when they are affected the consquent disability is serious.
7. Osteoarthritis
It is a common cause of severe disablement especially in elderly. It also affect young persons, when there has been previous damage from injury or disease.
8. The irrilable hip
Transient hip pain and restriction of movement in an otherwise healthy child. It is the commonest cause of hip pain in childern. Boys are commonly affected. (age group -6-12 yrs of age) Presents with pain and a limp often intermittant & following activity and extermes of all movements are limited

MEDICINES FOR HIPJOINT - DISLOCATION
Synthesis Reportory
Ext. Dislocation-Hip, spontaneous dislocation of :-
CALC, CAUST (3+)
Calc flor, colo, Rhus tox, Thuja (2+)
-pain from :- carb.ani, dros, kali io, Nit, acid
-Sitting down - Ipecac,