summary Hip Osteoarthritis is degenerative disease of the hip joint that causes progressive loss of articular cartilage of the femoral head and acetabulum. Diagnosis can be made with plain radiographs of the hip. Treatment is observation, NSAIDs, and corticosteroids for minimally symptomatic patients. Hip arthroplasty is indicated for progressive symptoms with severe degenerative disease. Epidemiology Incidence hip OA (symptomatic) 88 per 100,000 per year knee OA (symptomatic) 240 per 100,000 per year Risk factors modifiable articular trauma muscle weakness heavy physical stress at work high impact sporting activities non-modifiable gender females >males increased age genetics developmental or acquired deformities hip dysplasia slipped capital femoral epiphysis Legg-Calvé-Perthes disease Etiology Pathophysiology pathoanatomy articular cartilage increased water content alterations in proteoglycans eventual decrease in amount of proteoglycans collagen abnormalities organization and orientation are lost binding of proteoglycans to hyaluronic acid synovium and capsule early phase of OA mild inflammatory changes in synovium middle phase of OA moderate inflammatory changes of synovium synovium becomes hypervascular late phases of OA synovium becomes increasingly thick and vascular bone subchondral bone attempts to remodel forming lytic lesion with sclerotic edges (different than bone cysts in RA) bone cysts form in late stages Cell biology proteolytic enzymes matrix metalloproteases (MMPs) responsible for cartilage matrix digestion examples stromelysin plasmin aggrecanase-1 (ADAMTS-4) tissue inhibitors of MMPS (TIMPs) control MMP activity preventing excessive degradation imbalance between MMPs and TIMPs has been demonstrated in OA tissues inflammatory cytokines secreted by synoviocytes and increase MMP synthesis examples IL-1 IL-6 TNF-alpha Genetics inheritance non-mendilian genes potentially linked to OA vitamin D receptor estrogen receptor 1 inflammatory cytokines IL-1 leads to catabolic effect IL-4 matrilin-3 BMP-2, BMP-5 Other factors rapidly progressive osteoarthritis (RPOA) drug toxicity cortisone injections high doses (>80 mg) and multiple injections have been associated with RPOA cytokine-mediated immunological mechanisms autoimmune reactions inciting subchondral insufficiency fractures Classification Tonnis Classification Grade 0 Normal radiographs Grade 1 Sclerosis of femoral head and acetabulum Slight joint space narrowing Slight lipping at joint margins Grade 2 Small cysts in femoral head/acetabulum Moderate joint space narrowing Moderate loss of head sphericity Grade 3 Large cysts in femoral head/acetabulum Joint space obliteration/severe narrowing Severe femoral head deformity vs. AVN Presentation History identify age, functional activity, pattern of arthritic involvement, overall health and duration of symptoms Symptoms function-limiting hip pain effect on walking distances pain at night or rest hip stiffness mechanical instability, locking, catching sensation Physical exam inspection body habitus gait leg length discrepancy skin (e.g. scars) range of motion lack of full extension (>5 degrees flexion contracture) lack of full flexion (flexion < 90-100 degrees) limited internal rotation Neurovascular exam straight leg test negative Imaging Radiographs recommended views standing AP pelvis AP + lateral hip optional views false profile view (e.g. hip dysplasia) findings osteoarthritis joint space narrowing osteophytes subchondral sclerosis subchondral cysts pelvic obliquity may be secondary to spinal deformity may cause leg-length issues acetabular retroversion makes appropriate positioning of acetabular component more difficult intraoperatively Studies Histology loss of superficial chondrocytes replication and breakdown of the tidemark fissuring cartilage destruction with eburnation of subchondral bone Treatment Nonoperative NSAIDs and/or tramadol indications first line treatment for all patients with symptomatic arthritis technique NSAID selection should be based on physician preference, patient acceptability and cost walking stick decreases the joint reaction force on the affected hip when used in the contralateral upper extremity weight loss, activity modification and exercise program/physical therapy indications first line treatment for all patients with symptomatic arthritis BMI > 25 technique exercise aimed at increasing flexibility and aerobic capacity corticosteroid joint injections indications can be therapeutic and/or diagnostic of symptomatic hip osteoarthritis use for short-term pain relief strongly supported in 2013 AAOS CPG controversial treatments acupuncture viscoelastic joint injections glucosamine and chondroitin Operative arthroscopic debridement indications controversial degenerative labral tears not recommended for Tönnis grade 2 radiographic arthrosis high rate of conversion to arthroplasty periacetabular osteotomy +/- femoral osteotomy indications symptomatic dysplasia in an adolescent or young adult with concentrically reduced hip and mild-to-moderate arthritis outcomes mixed results literature suggest this can delay need for arthroplasty femoral head resection indications pathological hip lesions painful head subluxation hip resurfacing indications young active, male, patients with hip osteoarthritis increasing concern for metal-on-metal adverse events, procedure therefore decreasing in use total hip arthroplasty (THA) indications end-stage, symptomatic or severe osteoarthritis arthritis preferred treatment for older patients (>50) and those with advanced structural changes recommendation is to wait at least 3 months after ipsilateral intaarticular hip injection to decrease risk of prosthetic joint infection