The Painful Hip - by drdoc on-line
  Differential Diagnosis of the Painful Hip
 

The symptoms of hip pain presents frequently to the practitioner, and a systematic approach is necessary to diagnose the exact cause. In order to do this, a basic knowledge of the regional anatomy is required. In general, pain may arise from either an articular origin, an extra articular or soft tissue source, or from a distant referred site. Once an anatomical diagnosis of the origin of the pain has been made, appropriate investigations, can be done and a specific disease entity can be ascribed to the symptoms and signs, and appropriate therapy initiated, Therefore a basic understanding of the regional anatomy is useful, to understand the pathology better.


THE HIP JOINT : ANATOMY

The hip joint is a ball and socket joint between the head of femur and the acetabulum of os coxae. The articular capsule encloses the head and the greater part of the neck of femur. It is attached to the circumference of the acetabulum close to the edge. Below, it attaches anteriorly to the anterior trochanteric line and posteriorly to the neck of the femur. Anteriorly the capsule is thickened as the iliofemoral ligament. This prevents over-extension. Medially the capsule is thickened to form the pubofemoral ligament. The acetabular margin is ringed by the labrum acetabulare which deepens the socket. The head of femur is connected with the hip bone by the ligament of head of femur which connects the pit on the head and the margins of the acetabular notch.


MUSCLES OF THE HIP JOINT

1. Hip flexors Iliopsoas sartorious Rectus femoris
2. Abductors Gluteus medius (inserts into greater trochanter)
3. Adductors Adductor brevis/longus/magnus Gracilis Pectineus
4. Extensors Hamstrings Gluteus maximus (Inserts into the gluteal tuberosity and joins tensor fascia lata distally to form the iliotibial tract.)


BURSAE OF THE HIP REGION

1. Iliopsoas bursa anterior to psoas
2. Trochanteric bursa between gluteus maximus and the postero-lateral greater trochanter
3. Ischiogluteal bursa overlying ischial tuberosity


HIP JOINT SYNDROMES

Problems that present with pain in the hip region must be differentiated between problems located in the hip joint and capsule itself, and extraarticular syndromes (Table 1). In general, passive movement is not painful in extraarticular disorders, whereas resisted or active movement will be painful, especially in the direction of action of the affected muscle or tendon. In an articular problem, active and passive movement will both be painful. In particular, the movements of abduction and internal rotation of the hip joint are most sensitive to pain and limitation in articular disease. This pattern constitutes the "capsular pattern" of the hip joint.


1.: ARTICULAR DISEASE

It is important to observe the gait of the patient and the posture. A pelvic tilt may be due to a structural scoliosis, a leg length discrepancy, or hip disease itself. Observation may reveal contractures or gait disturbance. With an antalgic gait, the patient leans over the diseased hip during the period of weight bearing, placing the body weight directly over the joint to avoid contraction of the hip abductors.
A Trendelenburg gait is noted if there is a weakness of the hip abductors, or in the presence of a painful hip. In the assessment of the hip joint, the hip is passively taken through it's range of movement.

Normal ranges of movement are:

flexion 120 degrees
abduction 45 degrees
adduction 20-30 degrees
ext rotation 45 degrees
int rotation 40 degrees

Pain and/or limitation of movement on passive motion may be noted, especially on abduction and internal rotation - the capsular pattern. Flexion contracture of the hip, is assessed by flexing the opposite hip, to remove any lordosis and then extending the ipsilateral hip as much as possible. The fabere test may be done. This consists of flexion, abduction, external rotation and then extension of the hip, which produces pain. The Trendelenburg test of abductor function, in which the patient, whilst standing, is asked to lift the leg of the affected side off the floor. In abductor mechanism weakness, or if inhibited by pain, the pelvis will tilt downward on the affected side, instead of lifting, as in normal people. Leg length discrepancy, is measured by measuring the distances between medial malleolus and the anterior superior iliac spines. A difference of more than 1cm is significant.

Once the anatomical diagnosis is made, specific investigations can then be done to establish the specific pathological diagnosis. In general, different disorders are seen at different age of onset of disease (table 2).

Congenital dislocation of the hip, is caused by ligamentous/joint laxity, or acetabular dysplasia, and is characterised by limited abduction of the hip. Asymmetry may be noticed by the mother, as well as difficulty applying napkins. If bilateral, asymmetry may not be noted. A limp becomes apparent once walking commences. Abduction of the flexed hip is limited, on examination. Diagnosis is confirmed on X-Ray.

Perthes disease occurs because of partial or complete avascularity of the femoral head. Initially, the bony femoral head is normal on X-Ray, but then stops enlarging. The cartilaginous sheath continues to grow, receiving nourishment from the synovial fluid, and the joint space increases in size. Subchondral fractures then occur and new bone is laid down, as new blood vessels enter the head. This ossification appears denser, whilst the metaphysis appears rarified due to hyperaemia. The dead bone reabsorbs but bony flattening of the head and epiphyseal displacement may remain, and predispose to secondary degeneration in the future. Clinically, the child presents with pain and an irritable hip. In the early phase, the X-Ray may be normal, and bone scan may demonstrate the abnormality. Later, as the irritability subsides, pain may subside and the X-Ray changes are more pronounced.

Slipped epiphysis occurs in adolescents, with displacement of the upper femoral epiphysis at the growth plate. The majority are gradual onset, frequently with a history of trauma. The leg is externally rotated, and shortened. The hip is limited in abduction and internal rotation. Diagnosis is made on X-Ray with the line of the superior margin of the neck of femur, remaining superior to the head, rather than passing through it. (Trethowan's sign). Hip involvement in Juvenile chronic arthritis depends on the specific subtype of disease involvement.

Inflammatory arthropathy, as seen in Juvenile rheumatoid, or juvenile ankylosing spondylitis is characterised by pain, stiffness, joint limitation, in the capsular pattern, and concentric joint space narrowing on X-Ray. The head of femur migrates axially, and osseous erosions may be identified. Bony ankylosis may be seen in juvenile onset ankylosing spondylitis.

Transient idiopathic synovitis of the hip is a condition of unknown cause, which causes an irritable hip syndrome. The diagnosis is one of exclusion, as all tests and the X-Rays are normal. Osteoarthritis, is characterised by pain and joint limitation. Stiffness is usually of short duration and the discomfort is worse with weight bearing, activity and through the day, rather than on waking in the morning. X-Ray changes are usually on the upper aspect of the articulation, with superior migration of the femoral head. Osteophytes, sclerosis and cyst formation, of the femoral and acetabular surfaces are common.

Rheumatoid arthritis results in a bilateral and symmetrical involvement of the femoral head and acetabulum. Disease of the hip is usually seen in long-standing and more severe disease. There is loss of joint space as a result of destruction of the cartilage. Osteophytes are not seen as prominently as in osteoarthritis. There are frequently erosions, cysts and areas of local sclerosis.

Seronegative spondyloarthropathies also are characterised by diffuse inflammatory disease with axial migration of the head into the acetabulum. The changes differ from Rheumatoid arthritis, by the presence of osteophytosis, and ankylosis can also occur.

Infections may be bacterial ; acute or chronic, or fungal. Pyogenic infections have loss of joint space, generally diffuse, and are associated with porosis and osseous erosions. Tuberculous arthritis produces regional osteoporosis. Bony erosion occurs before cartilage loss, but this follows later in the disease. Complete destruction of the femoral head may be seen.

Osteonecrosis is caused by a number of conditions, producing avascular necrosis of the femoral head (Table 3). Diagnosis at an early stage is usually confirmed by either Bone Scan or Magnetic resonance imaging, as the early X-Ray shows no changes. Later there is flattening of the superior aspect of the femoral head, and loss of superior joint space. Ultimately, secondary degenerative changes of osteoarthritis supervene.

Gout rarely affects the hip joint, but pseudogout, with deposition of calcium pyrophosphate dihydrate crystal may involve one or both hips, with chondrocalcinosis, symmetrical joint space narrowing, and osteophytosis.

Chondrocalcinosis may be identified at other sites, especially, the knees and symphysis pubis. Paget's disease affects bone turnover, and can be identified on X-Ray, affecting adjacent bone. Idiopathic Chondrolysis is rare, and causes femoral head rarefaction and diffuse loss of joint space, with axial migration of the femoral head.

Regional Osteoporosis of the Hip, affects one or both hips, and is a transient syndrome of hip pain, improving spontaneously over weeks to months. There is regional osteopenia, with no reduction in joint space. The problem has a characteristic appearance on Magnetic resonance imaging, A radionuclide scan can also assist in diagnosis.

Idiopathic Synovial Osteochondromatosis is due to the formation of multiple foci of metaplastic hyaline cartilage within the synovium. Calcification of these may occur. It produces monoarticular disease with intra-articular masses, (which may be calcified), seen on X-Ray, or identified on arthrography. Soft tissue swelling and osseous erosions may be seen, with relative maintenance of the joint space. Secondary mechanical damage can occur to produce osteoarthritic changes within the joint.

Pigmented Villonodular synovitis, is seen in young adults, producing a chronic monoarticular arthropathy, with no other signs of generalised disease. The knee is most commonly affected, but hip disease can occur. X-Ray shows only soft tissue thickening. Diagnosis is confirmed by arthroscopic biopsy, revealing proliferative brown stained synovium.

Familial Acetabular protrusion is seen particularly in females and results in bilateral abnormality, with progressive acetabular protrusio, identified on X Ray. Ultimately there is also loss of the joint space.


2. EXTRA-ARTICULAR SYNDROMES

Myofascial Pain Syndromes Of The Hip Region.

These syndromes, are frequently seen, and should be differentiated from articular disease, as therapy can often be given locally, with most gratifying results. (Table 4).

a) Snapping hip syndrome : This is a painless condition, where a snapping sound is heard by the patient on hip flexion and extension. It is due to a slipping over the greater trochanter, of the iliotibial band (an extension of the fascia lata between the iliac crest, sacrum and ischium, stretching over the greater trochanter, to the lateral femoral condyle, tibial condyle and fibular head.

b) Fascia lata syndrome : This is associated with pain and trigger points over the lateral thigh region.

c) Trochanteric bursitis : This is a commonly seen problem, presenting with pain over the lateral hip area and buttock. The patient may note difficulty lying on the affected side. Examination reveals local tenderness over the greater trochanter area, and resisted abduction may be tender. Passive abduction is painless.

d) Iliopectineal Bursitis : The bursa lies between the iliopsoas muscle and the iliopectineal eminence. Clinically, there is pain on resisted flexion, and tenderness overlying the capsule of the hip. Pain is felt over the anterior pelvis and groin area.

e) Iliopsoas Bursitis : Pain is felt over the anterior pelvis region and is accentuated on resisted flexion.

f) Ischial Bursitis : This produces pain over the ischial prominence and hence is painful on sitting. The sciatic nerve lies closely related to the bursa anatomically, and may be subjected to local irritation.


3. REGIONAL NERVE ENTRAPMENT SYNDROMES

a) Abdominal Cutaneous nerve : Entrapment occurs as the nerve emerges through a fibrous ring in the abdominal wall. Focal tenderness is felt at this site, and pain may be felt over the low abdominal wall.

b) Obturator Nerve : Usually this follows trauma with pelvic fracture or osteitis. Pain is felt in the groin and down the inner thigh. The pain is aggravated by hip movement.

c) Lateral Femoral Cutaneous Nerve: (Meralgia Paraesthetica). This is a common entrapment syndrome, occurring at the anterior superior iliac spine, as the nerve passes through the inguinal ligament. Pain is felt over the upper anterolateral thigh region. It is caused by trauma, prolonged sitting with crossed legs, bulging abdominal girth, corsets and occasionally from car seat belts.


4. REFERRED PAIN

The examiner should always remember the problem of referred pain, especially from the lumbosacral spine, and from the knee. The clinical examination will usually identify this and differentiate the origin of the pain from hip-pain itself.


TABLE 1.
CAUSE OF HIP REGION DISCOMFORT

1) Articular source.
2) Extra-articular.: Soft tissue Rheumatism.including muscle / tendon / ligaments / bursa.
3).Nerve entrapment syndromes.
4) Referral from distant site.


TABLE 2
AGE AND PROBABLE DIAGNOSIS

BIRTH
CONGENITAL DISLOCATION OF THE HIP.

0-5 YEARS
INFECTIONS.

5-10 YEARS
PERTHES DISEASE.

10-15 YEARS
SLIPPED EPIPHYSIS.
INFECTIONS.
JUVENILE RHEUMATOID ARTHRITIS.
JUVENILE ANKYLOSING SPONDYLITIS
TRANSIENT IDIOPATHIC SYNOVITIS.

ADULTHOOD
OSTEOARTHRITIS.
RHEUMATOID ARTHRITIS.
REACTIVE / SERONEGATIVE SPONDYLOARTHROPATHIES.
INFECTIONS (ACUTE/CHRONIC).
OSTEONECROSIS.
TRAUMA.
GOUT / PSEUDOGOUT
PAGETS
IDIOPATHIC CHONDROLYSIS
TRANSIENT OSTEOPOROSIS OF THE HIP
SYNOVIAL OSTEOCHONDROMATOSIS
PIGMENTED VILLONODULAR SYNOVITIS
FAMILIAL ACETABULAR PROTRUSION


TABLE 3
CAUSES OF AVASCULAR NECROSIS OF THE FEMORAL HEAD

Alcohol
Trauma
Systemic Lupus Erythematosus
Rheumatoid arthritis
Steroid therapy / Cushing's syndrome
Air / fat embolism
Caissons disease
Haemoglobinopathy,
Sickle cell syndrome
Tumour / Haematological malignancy
Gaucher's Disease.


TABLE 4.
EXTRA ARTICULAR SYNDROMES

a) Snapping hip syndrome
b) Fascia lata syndrome
c) Trochanteric bursitis
d) Iliopectineal Bursitis
e) Iliopsoas Bursitis
f) Ischial Bursitis

 

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Dr D Gotlieb. -drdoc on-line
MBChB FCP(SA)
Constantiaberg Mediclinic Cape Town
Original Article -copyright

Published in Rheumatology News (South Africa)