The basics - Hip pain

Recognising hip pain can be difficult, explains Dr Louise Warburton.

Hip pain can originate from the back, groin structures or the actual hip joint.

It can be difficult to differentiate between the possible origins of the pain, but taking a good history is the best start in unravelling the diagnosis.

Ask when the pain was first felt and if anything caused it. Does the pain radiate anywhere or is there any nocturnal pain and is the patient limping?

SPLX-ray of the hip joint confirming osteoarthritis: the joint space is narrowed causing painful movement

Pain felt behind the hip joint or radiating down the side of the leg is likely to be coming from the back.

The age of the patient will also influence the history taking and examination.

Children
In young children, the diagnosis could be Perthes' disease; this is a type of avascular necrosis (AVN) of the femoral head and causes a limp in children typically aged between four and eight years.

In older children, a slipped upper capital epiphysis could be the cause of the pain and is diagnosed on X-ray or MRI scan.

Always refer children with hip pain for an urgent paediatric or orthopaedic assessment.

Lumbar spine pain
Discogenic back pain can radiate down the leg and sometimes into the anterior thigh. Femoral nerve compression will cause referred pain around the hip joint and into the thigh.

It can be distinguished from hip joint pain by assessing the range of movement in the lumbar spine, which is likely to be reduced if there are disc problems.

Also, the femoral nerve stretch test may be positive; lie the patient on the opposite side to the pain and extend the hip joint as far as possible with a straight leg. Then bend the knee, which will stretch the femoral nerve and cause pain if the nerve is trapped or irritated anywhere.

A slump test will elicit pain if there is any sciatic nerve entrapment.

Dural irritation can cause referred pain into the buttock and upper leg and will do this without positive femoral nerve or sciatic stretch tests. Pain comes directly from the dura around the spinal cord. This is really a diagnosis of exclusion and can be managed with physiotherapy or epidural or nerve root blocks.

Learning points

  • Hip pain can originate in the back, groin or the actual hip joint.
  • Pain felt behind the hip joint is likely to be coming from the back.
  • Always refer children with hip pain for urgent assessment.
  • Sudden, severe unilateral hip pain is a red flag symptom.
  • Osteoarthritis is the most common presentation of true hip pain; the earliest clinical examination finding is loss of internal rotation.

The hip joint
Pain from the hip joint is usually felt in the crease of the groin and thigh. In primary care, osteoarthritis of the hip joint will probably be the most common presentation of true hip pain.

Examining the range of movement in the hip will classically reveal a reduction in internal rotation of the joint; external rotation is well preserved. Flexion and extension are slightly reduced and painful. Diagnosis is confirmed on X-ray.

Functional assessment of the arthritic hip is possible with the Oxford Hip Questionnaire (see http://phi.uhce.ox.ac.uk/ox_scores.php).

This allows a score of disability to be made and gives the referring doctor some idea of when to refer for hip replacement surgery.

Inflammatory arthritis can affect the hip joint, especially in the spondyloarthritides. Again the loss of movement in the joint will be in a capsular pattern as described for osteoarthritis of the hip and there will be pain and a limp.

Inflammatory markers may be raised and there will be other inflamed joints found on examination.

Red flags
Acute unilateral hip pain of sudden onset and severe enough to cause nocturnal wakening is a red flag scenario. Urgent X-ray should be arranged to exclude a fracture or AVN of the femoral head.

AVN is more common after high-dosage steroid treatment but can occur suddenly. Other risk factors are recent fracture of the femoral neck and after posterior dislocation of the hip.

AVN is treated with hip replacement surgery, if conservative management fails.

In pregnant women, a condition called idiopathic transient osteoporosis of the hip can cause severe pain in the hip.

Trochanteric bursitis
The trochanteric bursa lies over the greater trochanter of the femur and under the thick, fibroelastic iliotibial band (ITB).

During walking and running, the ITB moves over the greater trochanter and over the trochanteric bursa. The bursa may become inflamed if the ITB is too tight, or direct trauma to the bursa may cause inflammation.

Gluteal muscle weakness is common if there has been a disease process in the hip joint or in the back. It can be detected by asking the patient to stand on one leg and looking from behind for a drop in the iliac crest on the side unsupported (the Trendelenburg test). Normal strength gluteals hold the pelvis level and prevent a drop or sag.

Weakness in the gluteal muscles can also cause inflammation of these other bursae, usually because the greater trochanter will rotate internally, causing medial knee rotation and foot over-pronation. This stretches the bursae and can cause inflammation.

Patients complain of pain over the lateral side of the thigh and the bursa or bursae are tender. Again, patients will describe the pain as coming from the hip, when it is not really related to the hip joint.

Treatment is by injection and/or assessment of the ITB and gluteal muscles by a physiotherapist with exercises to improve strength and co-ordination.

Meralgia parasthetica
Meralgia parasthetica is entrapment of the lateral cutaneous nerve of the thigh as it emerges from the superficial fascia. Tight clothing can sometimes compress the nerve as well.

Patients complain of numbness and pain over the anterior skin of the thigh and sometimes an area of reduced sensation can be demonstrated. Occasionally surgery to the fascia is necessary to release the nerve.

Psoas muscle lesions
The psoas is a flexor and external rotator of the hip and can be injured in sprinting and kicking and in high knee lift exercises. Pain is felt anteriorly and just lateral to the femoral canal. If passive hip flexion is painful, then the psoas bursa is also inflamed.

A psoas abscess is a condition much described to medical students and was common when TB was much more prevalent. It causes pain and spasm of the psoas muscle and consequent flexion of the hip.

Pubic symphysis pain
Pubis dysfunction is common in pregnancy and is due to the normal stretching of pelvic ligaments as pregnancy progresses. The symphysis ligament stretches, allowing the symphysis to move and this causes pain.

Rest and a pelvic brace can help. Physiotherapists can offer treatment and advice.

Athletes can experience traumatic disruption of the pubic symphysis due to overzealous training programmes. Pain is experienced in the groin and the patient is tender over the symphysis pubis.

Conclusion
Hip joint pain can be tricky to assess. A thorough history and examination will usually elicit the cause, and physiotherapy colleagues will be very helpful in further assessment and treatment.

  • Dr Warburton is a GPSI in rheumatology in Ironbridge, Shropshire

Idiopathic transient osteoporosis
Clinical features

  • Uncommon disease which is a diagnosis of exclusion
  • Most often seen in women during the third trimester of pregnancy
  • Typically there is no antecendent trauma
  • Up to 40 per cent of patients may show involvement in other joints

Clinical findings

  • Groin pain, and mild limited range of motion of hip
  • Patients may be unable to bear weight even if hip pain is minimal
  • ESR may be elevated
CAUSES OF HIP PAIN
Cause
Age group Intra-articular Periarticular Referred
Childhood
(2-10 years)
Developmental dislocation of hip
Irritable hip
Rickets
Perthes' disease
Osteomyelitis Abdominal
Adolescence (10-18 years) Slipped upper femoral epiphysis
Torn labrum
Trochanteric bursitis
Snapping hip
Osteomyelitis
Tumours
Abdominal
Lumbar spine
Early adulthood (18-30) Inflammatory arthritis
Torn labrum
Bursitis Abdominal
Lumbar spine
Adulthood (30-50 years) Osteoarthritis
Inflammatory arthritis
Osteonecrosis
Transient osteoporosis
Bursitis Abdominal
Lumbar spine
Old age
(>50)
Osteoarthritis
Inflammatory arthritis
Abdominal
Lumbar spine
Source: Orthopaedics in Primary Care. Carr A, Hamilton W. London: Elsevier, 2005

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