Clinical presentation and biomechanics
Patients present with complaints of dull, aching, and diffuse pain, most commonly localized in the groin area and exacerbated by axial loading (walking, climbing stairs). A characteristic sign of limited mobility is the patient's inability to reach their shoes to tie their laces.
Examination reveals an antalgic gait. Due to pain, the patient subconsciously protects the joint: when bearing weight on the affected leg, they avoid using the hip abductors, as their contraction significantly increases joint compression. Instead, the patient sharply leans their torso toward the affected joint, visually resembling a Trendelenburg gait. In cases of severe joint collapse, limb shortening is observed.
Instrumental and laboratory diagnostics
The gold standard for diagnosis is radiography. It is mandatory to obtain an anteroposterior view of the pelvis in a standing position and a lateral view of the hip joint. The study is performed bilaterally for comparison.
The classic radiographic tetrad of osteoarthritis includes:
- Joint space narrowing.
- Subchondral sclerosis — thickening of the underlying bone in response to abnormal mechanical loading.
- Formation of osteophytes (bone spurs) at the periphery.
- Appearance of subchondral cysts.
In late stages, when the cartilage is completely lost, bone-on-bone friction leads to eburnation (eburnation) — hardening and "polishing" of the exposed bone tissue. MRI and CT are not used in routine practice and are only needed to rule out other pathologies or for surgical planning. There are no specific laboratory tests for osteoarthritis. Inflammatory markers (ESR, CRP) and antibodies (RF, anti-CCP) are tested exclusively to rule out autoimmune processes such as rheumatoid arthritis.
Differential diagnosis
The clinician's main task is to ensure that the radiographic changes are indeed the cause of the pain, as there is a clinicoradiological mismatch (severe pain with minimal changes and vice versa).
- Pain localization: pain along the lateral aspect of the thigh usually indicates greater trochanteric bursitis (trochanteric pain syndrome). Pain radiating to the buttocks is typical of spinal stenosis or lumbar disc pathology (rule: joint pathology rarely causes pain above the waistline).
- Mild radiographic changes: if the pain is severe but the joint is preserved, femoroacetabular impingement or a labral tear should be ruled out.
- Osteonecrosis: can occur without a history of trauma; in such cases, other joints must be examined.
To differentiate from sacroiliac joint (SIJ) pathology, the FABER test (Flexion, ABduction, External Rotation) is used. The hip is flexed, abducted, and externally rotated, placing the ankle on the healthy leg, after which the physician gently presses on the knee. If pain occurs anteriorly in the groin, it is a hip joint pathology. If it occurs posteriorly on the contralateral side, the problem is in the SIJ.
Briefly: answers to topical questions
What are the main manifestations of greater trochanteric bursitis (trochanteric pain syndrome) during differential diagnosis?
The main manifestation of greater trochanteric bursitis in differential diagnosis is pain along the lateral aspect of the thigh. This pain rarely originates from the hip joint itself, which helps distinguish it from osteoarthritis.
Clinical features:
- Greater trochanteric pain syndrome (greater trochanteric pain syndrome) is an umbrella term that includes gluteal tendinopathy and bursitis.
- Palpation tenderness is the most frequent symptom upon examination, localized in the region of the greater trochanter.
Objective instrumental or laboratory criteria are absent, so the diagnosis is made exclusively based on the clinical presentation.
What is femoroacetabular impingement and when is it ruled out?
Femoroacetabular impingement is a clinical syndrome associated with excessive bone overgrowth of the femur, pelvic bones, or both structures, causing abnormal contact between the proximal femur and the acetabulum during hip flexion and rotation.
There are two main types:
- Cam impingement (cam impingement) is an abnormal overgrowth on the femoral neck or head.
- Pincer impingement (pincer impingement) is an abnormal overgrowth of the acetabular rim.
In cases of hip pain with only minor radiographic changes, femoroacetabular impingement is considered a possible cause of symptoms, along with labral tears.
Radiological tetrad of osteoarthritis: Joint space narrowing, Sclerosis, Osteophytes, Cysts (mnemonic JSOC).
Class and exam questions
Does the intensity of pain always correspond to the degree of joint destruction on radiographs?
No, clinicoradiological mismatch is frequently observed. Pronounced changes on imaging may be accompanied by minimal discomfort, while severe pain is possible with an almost normal radiograph (in the latter case, other causes of pain should be sought).
Why are blood tests ordered when osteoarthritis is suspected?
To rule out systemic inflammatory diseases. Tests for rheumatoid factor (RF), anti-cyclic citrullinated peptide (anti-CCP) antibodies, C-reactive protein, and ESR help distinguish degenerative coxarthrosis from rheumatoid arthritis.
How to differentiate hip pain from spinal pathology?
Typically, pain from the hip joint is localized in the groin and does not rise above the waistline. Pain radiating to the buttocks or the posterior thigh more often indicates lumbar disc issues.
What else to study on this topic
- Pathogenesis: the role of inflammatory cytokines and proteolytic enzymes in OA.
- Biomechanics: how a cane in the contralateral hand reduces joint compression.
- Risk factors: the impact of developmental dysplasia and slipped capital femoral epiphysis on joint mechanics.
- Conservative management: NSAIDs, core muscle physical therapy, and intra-articular injections.
- Technique for intra-articular hip injections under ultrasound and fluoroscopic guidance.
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