Clinically, it is important to differentiate painful OA from three other causes of regional or generalised joint pain. The European League Against Rheumatism EULAR (2010) made key recommendations for the diagnosis of OA. These were produced based both on expert opinion and a systematic literature review. The main clinical features of OA make it, in general, an easily recognisable condition. These are as follows:
- Increased age: it is unusual to develop the disease before the age of 40 years.
- Pain: use related joint pain, relieved by rest. In more advanced cases, rest pain and night pain may also develop.
- Stiffness: most people with symptomatic OA of large joints experience short-lasting inactivity stiffness of joints, which wears off after a few minutes with use.
- Reduced movement: the range of movement of the joint is often restricted, and there is generally pain with movement, particularly at the end of the range.
- Swelling: many OA joints develop palpable firm swellings at the joint margin due to the formation of osteophytes. Some have minor tissue swelling due to secondary synovitis.
- Crepitus: OA joints often make a grinding noise or crack on movement.
A confident diagnosis of OA can be made without a radiographic examination.
Laboratory tests on blood, urine or synovial fluid are not required for the diagnosis of OA but may be used to confirm or exclude the co-existence of an inflammatory disease.
If palpable effusion is present, synovial fluid should be aspirated and analysed to exclude inflammatory disease and to identify urate and calcium pyrophosphate crystals. Red flags (e.g. severe local inflammation, erythema, progressive pain unrelated to usage) suggest sepsis, crystals or serious bone pathology. Involvement of other joints may suggest a wide variety of alternative diagnoses. Other possible considerations are referred pain, ligamentous and meniscal lesions and localised bursitis.
For hip OA the American College of Rheumatology (ACR) uses the following criteria for the diagnosis of hip OA (Table 1). There is little research available regarding the sensitivity and specificity of the history taking and examination process relying much on level 5 evidence i.e. expert opinion. The following history taking and examination process is not meant to cover all conditions encountered by a primary care practitioner but offers a reasonable approach in assessing most commonly encountered conditions experienced by a patient presenting with hip pain.
First assess function; the assessment of gait should be undertaken as the patient enters the examination room or asked to walk up and down the room. Second with the patient standing assess whether or not the anterior superior iliac spines are level. If they are not there may be some leg length discrepancy accountable for this.
Table 1: ACR criteria for the diagnosis of hip OA
|Combined clinical and radiographic criteria (traditional format)||Clinical Criteria (tree format)||Combined clinical and radiographic criteria (tree format)|
|Hip Pain plus at least 2 of the following: ESR<20mm/h Radiographic or acetabular osteophytes Radiographic joint space narrowing (superior, axial or medial)||Hip pain AND internal rotation< 15° and ESR<45mm/hr (if ESR not available use hip flexion≤115°) OR hip internal rotation< 15° and pain on hip internal rotation AND morning stiffness<50 mins. AND age >50 years||Hip pain AND femoral and/or acetabular osteophytes on radiograph OR ESR≤20mm/h AND axial joint-space narrowing on radiographs.|
|Sensitivity89%||Sensitivity 86%||Sensitivity 91%|
|Specificity 91%||Specificity 75%||Specificity 89%|
|Adapted from Altman R et al. Arthritis Rheum 1991|
As the site of the hip pain varies, so does the aetiology, so when assessing whether the hip pain is anterior, lateral or posterior, the patient should be asked about the onset of the pain i.e. sudden or insidious, the kind of movements or positions that reproduce the pain and the effect of movement and weight bearing activity has on the pain. Third the joint above and below the affected one should be examined as sometimes pain can be referred to a more distal joint, for example hip pathology causing knee pain. The assessment should ascertain whether just the one joint is involved or whether there is evidence of a widespread disorder.
In general, osteoarthritis and trochanteric bursitis are more common in older, less active patients, whereas stress fractures, iliopsoas strain or bursitis, and iliotibial band syndrome are more common in athletes. Complaints of a ‘snapping sensation’ may indicate iliopsoas bursitis if the snapping is anterior, or iliotibial band syndrome if the snapping is lateral.
Further exploration of the site of hip pain follows below. It offers a reasonable way to diagnose hip pathology of commonly encountered conditions treated in primary care.
While the main component of pain in OA is nociceptive, there is recent evidence suggesting that patients may have a neuropathic component to their pain (a quarter of the cohort examined had neuropathic OA pain in one study – Hochman et al 2007). If this is the case, traditional pharmacotherapy will not be effective. If patients describe strange symptoms and/or pain is resistant to the more traditional drug therapies, it may be worth considering a neuropathic pain (NP) questionnaire which may facilitate the identification of a neuropathic component to osteoarthritis (OA) pain. An existing questionnaire, the painDETECT, has been modified for use in knee OA and administered to measure the prevalence and correlates of NP symptoms among adults with this condition.