1. The most important part of the consultation is the history
Never assume that pain described as coming from the hip will actually be originating in the hip joint. What patients mean by ‘hip pain' is often not what you might consider hip pain.
Ask where the pain is felt, asking the patient to point to the site of pain. Hip-joint pain is felt anteriorly in the groin crease. Pain round the back or side of the hip is unlikely to originate in the joint space. Ask what makes the pain worse and if there is any nocturnal pain. The age of the patient will influence history taking and examination.
2. In young children, think of Perthes' disease, particularly in boys
This is a type of avascular necrosis of the femoral head, causing hip pain and a limp in children aged four to eight years old, and is more common in boys than girls.
3. In older children, a slipped upper femoral epiphysis is a more likely cause of hip pain than Perthes' disease
Both conditions can be diagnosed on X-ray or MRI. Any hip pain in a child or adolescent should be treated as a red flag and urgent referral arranged to exclude the above conditions.
4. Pain coming from the lumbar spine is the condition most likely to be misdiagnosed as hip-related pain
Pain from the third and fourth lumbar segments, involving the femoral nerve, will result in pain felt over the anterior part of the thigh and around the groin. Pain from further up in the lumbar spine will cause pain radiating around the side of the abdomen and into the groin area.
The only way to tell for sure where the pain originates is to examine the patient. Examination of the spine as well as the hip joint is necessary. Check for reduced mobility in the lumbar spine and signs of radiculopathy by testing the straight leg raise – this will diagnose problems with the sciatic nerve – and the femoral nerve stretch test. Lie the patient prone, and extend the hip and bend the knee simultaneously, which stretches the femoral nerve.
5. Inflammatory arthritis of the hip joint will cause pain in the hip
Examination of the hip joint will reveal painful flexion and extension of the joint and a reduced range of movement. Internal and external rotation will also be reduced. It is worth testing inflammatory markers and rheumatoid factor if inflammatory arthritis is suspected.
Also, look out for signs of psoriasis as psoriatic arthropathy commonly affects the hip.
6. Be aware of trochanteric bursitis – sometimes referred to as lateral hip pain complex – as a cause of hip pain
Trochanteric bursitis is a term that can cover many problems around the insertion of the gluteal muscles onto the greater trochanter.
Originally, it was thought to be simply an inflammation of the bursa, but we now know that many conditions can cause pain in this area. Most commonly, there will be tendonopathy of the gluteal muscles' tendons. Sometimes it is better to use the term lateral hip pain complex, rather than trochanteric bursitis.
There may still be bursitis, but injecting the area is a quick fix, and it is better to enlist the help of a physiotherapist to assess gluteal muscle strength and treat the tendonopathy. Patients complain of pain over the lateral side of the thigh and the area is tender. Again, patients will describe the pain as coming from the hip, when it is not really related to the hip joint.
7. If patients complain of numbness over the anterior skin of the thigh, consider meralgia paraesthetica
This 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.
Sometimes an area of reduced sensation can be demonstrated. Occasionally, surgery to the fascia is necessary to release the nerve.
8. Get to know the psoas muscle
The psoas is a flexor and external rotator of the hip and can be injured in sprinting, kicking and 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. Medical students are often taught about a psoas abscess, a condition that used to be common when TB was much more prevalent. It causes pain and spasm of the psoas muscle and consequent flexion of the hip.
9. Be aware of the red flags for hip pain
The pelvic girdle is a common site for bony metastases and stress fractures may occur. Fractures also occur in the elderly with osteoporosis and in athletes.
Any unremitting hip pain should be investigated by X-ray and blood tests, checking ESR, CRP and protein electrophoresis, as well as Bence Jones proteins in the urine.
10. Pubic symphysis pain is another possible cause
Symphysis pubis dysfunction is common in pregnancy and is due to the normal stretching of pelvic ligaments as pregnancy progresses.
The syphysis ligament stretches, allowing the symphysis to move, and this causes pain. Rest and a pelvic brace can help. Physiotherapists offer treatment and advice. Athletes can experience traumatic disruption of the pubic symphysis caused by overzealous training programmes. Pain is experienced in the groin and the patient is tender over the symphysis pubis.
Dr Louise Warburton is a GPSI in rheumatology and musculoskeletal medicine in Shropshire, clinical teacher at Keele University and president of the Primary Care Rheumatology Society
The society's 25th annual conference runs from 17-19 November 2011 in York. Further details are available at www.pcrsociety.org
