Non-traumatic cases will typically present with mechanical pain of variable onset and severity and often difficult to localize. In early disease, the physical examination is usually normal and inevitably causes a delay in diagnosis.[4] A focused history should include recent trauma, steroid use, autoimmune disease, sickle cell, alcoholism, tobacco use, manual labor, change in gait, connective tissue disorders, insidious onset pain, and decreased range of motion.[8] 

Osteonecrosis of the Hip. Early stages are often asymptomatic. Hip pain and groin pain are the most common presenting symptoms and usually indicate late-stage progression. Associated symptoms can include referred pain to buttock and thigh. The majority of patients have pain at rest. Others include stiffness and changes in gait.[1]

Osteonecrosis of the Knee most commonly presents as acute onset knee pain that occurs while weight-bearing and at night. History of osteoporosis or osteopenia and no recent trauma are typical responses. On physical exam, pain with palpation over the medial femoral condyle and decreased range of motion are observed.[14]

Osteonecrosis of the Shoulder. This condition involving the proximal humerus is often associated with trauma and osteonecrosis elsewhere in the body. Pain is characterized as pulsating with radiation to the elbow and a decreased active range of motion.[15]

Osteonecrosis of the Talus is associated with polyarticular disease and trauma. Patients will often complain of pain and difficulty ambulating well beyond the expected recovery time following a traumatic event.[16][10]

Osteonecrosis of the Lunate and Scaphoid most often present without a history of trauma. Patients are usually skilled laborers and complain of unilateral pain on the wrist's dorsal and radial aspects. Decreased range of motion, wrist swelling, and weakened grip strength are other common findings.[13][17] 

Initial evaluation with plain radiographic films demonstrating two orthogonal views is the initial diagnostic standard, although in the early course of the disease they often appear normal. Magnetic resonance imaging is the recommendation for the detection of earlier stages of the disease due to its high sensitivity in detecting bone edema.[5]

Classification

Osteonecrosis of the Hip

Femoral head osteonecrosis falls into two classes: traumatic or atraumatic. Of the atraumatic cases, up to 70% may be bilateral.[18] Common classifications that map the phases of osteonecrosis of the hip include the Ficat and Arlet classification and the Steinberg classification.[19][20] Ficat and Arlet describe the four stages of disease progression based on clinical and radiographic findings. Stage 1 is the initiation of the disease without radiological findings. Stage IV is the end-stage with femoral head collapse, flattening, and narrowing of the joint space. The Steinberg classification incorporates the use of MRI to detect a pre-clinical lesion and also to assess the size of the lesion.

Osteonecrosis of the Knee

Spontaneous osteonecrosis of the knee (SONK) is the most common type.[21] Secondary osteonecrosis is commoner in a younger population and often associated with a number of risk factors common to all kinds of osteonecrosis as previously discussed. The third and rarest type is called post arthroscopic osteonecrosis and has been seen in 4% of patients having undergone an arthroscopic meniscectomy. SONK typically presents in the sixth decade of life and is more common in the female population. Classically it affects the medial femoral condyle (up to 94% of cases), and subsequent cadaveric studies have demonstrated a watershed area of the medial femoral condyle.[22][14] The overriding symptom is that of medial knee pain often mimicking a torn meniscus. The Koshino classification describes the four stages of disease progression.[22] Stage 1 describes clinical disease without a radiologically apparent disease. Stage 4 is the degenerative phase with osteosclerosis and osteophyte formation around the condyles.

Osteonecrosis of the Shoulder

Osteonecrosis of the shoulder most frequently results from trauma however it can arise from the causes outlined above, for instance, prolonged high-dose corticosteroid usage. Hertel et al.[23] showed that specific fracture plane combinations had associations with impaired head perfusion and that additional elements such as length of the posteromedial metaphyseal head extension and the integrity of the medial hinge were the key elements for the occurrence of osteonecrosis. Most of those fracture patterns with an increased risk of avascular necrosis had an anatomic neck component. Interestingly fracture-dislocations, and degree of displacement of the fragments do not predict an increased incidence of avascular necrosis of the humeral head although contradictory evidence does exist. Classification is the Cruess classification and uses five categories.[24] Stage 1 describes normal x-ray findings with pathology only recognized on MRI scans. Stage four demonstrates flattening of the humeral head with collapse. Stage five is the end-stage with degenerative changes that extend to the glenoid.

Osteonecrosis of the Talus

Most commonly caused by trauma resulting in displaced fractures to the neck of the talus. The incidence of avascular necrosis increases with co-existing dislocation at the ankle joint or subtalar joint. The talus body is often affected because of a predominate cartilaginous surface limiting its vascular supply.[25] The Hawkins classification best describes the disease progression. If osteonecrosis is to occur the pathognomonic subchondral lucency known as Hawkins sign will be absent on plain radiographs at 6-8 weeks.

Osteonecrosis of the Lunate

More commonly known as Keinbock’s disease involves a collapse of the lunate due to vascular insufficiency and osteonecrosis. A history of repetitive trauma, biomechanical factors related to ulna variance, and anatomic factors such as the presence of both dorsal and palmar blood supply may contribute to the risk of avascular necrosis. The Lichtman staging of Keinbock’s disease uses four stages. The first radiographic feature becomes apparent in stage 2 disease, represented by lunate sclerosis without height loss.[17] Lunate collapse and palmar scaphoid rotation is the radiologic feature in stage 3 disease. Intercarpal joint degeneration is the dominant feature of end-stage disease.[17]

Osteonecrosis of the Scaphoid

Known as Preiser disease, arises from an uncertain etiology. Risk factors include alcohol abuse, trauma, steroid use, and connective tissue disorders.[3][12] Typically it affects middle-aged males' dominant hand, although it can present bilaterally. A radiograph shows scaphoid sclerosis early in the disease process. Late-stage findings demonstrate cystic changes and fragmentation. MRI may detect T1/T2 signal changes throughout the scaphoid or specific to the proximal pole. The Herbert and Lanzetta classification system is used to assess progression. The system consists of four stages that begin with changes to the scaphoid's proximal pole, followed by eventual carpal collapse.[12]

Osteonecrosis of the Hip

Many patients will ultimately need a total hip arthroplasty however joint salvaging procedures such as core decompression report with varying results. Core decompression is most effective in the early stages of osteonecrosis and when the lesions only involve a small amount of the weight-bearing surface of the femoral head.[26] The procedure may use vascularised bone grafts or biologic agents that promote bone repair. Interestingly Zhao et al.[27] used perfusion studies to show core decompression is more effective in femoral heads with venous congestion that those with arterial compromise.

SONK 

The majority of cases resolve following a trial of protected weight-bearing and physiotherapy. As SONK is more common in the older person a unicompartmental knee replacement provides a good functional outcome with a relatively short rehabilitation time.[21] However, a total knee replacement may be more appropriate in larger lesions. Smaller lesions following intraosseous decompression have achieved good operative results.

Osteonecrosis of the Shoulder

Operative management is classified according to staging. For early disease, core decompression is the preferred treatment option. Humeral head resurfacing or hemiarthroplasty is recommended for moderate disease, reserving a total shoulder replacement in advanced disease.[10]

Osteonecrosis of the Talus

The incidence of osteonecrosis of the talus in talar neck fractures is reduced utilizing a procedure to achieve operative anatomic reduction and stable fixation.[5]

Keinbock’s Disease

Treatment in early-stage disease aims to revascularize the lunate either directly using bone grafts or indirectly utilizing procedures to offload the lunate. Immobilization, including external fixation, is often attempted in stage 1 and 2 disease.[17] Surgical options address the carpal collapse in stage 3, whereas advanced disease may warrant joint sacrificing procedures such as wrist arthrodesis.[17]

Preiser Disease

Early-stage treatment options involve immobilization, cortisone injections, radial wedge osteotomy, and bone graft. Later stages may warrant arthroscopic debridement, scaphoid excision, proximal row carpectomy, or even arthrodesis. Typically, surgical intervention is unavoidable in most cases.[12]

• Bone marrow edema syndrome (aka, transient osteopenia)[1]
• Complex regional pain syndrome
• Inflammatory synovitis
• Neoplastic bone conditions
• Osteoarthritis
• Osteochondrosis[9]
• Osteoarthritis
• Osteomyelitis
• Osteoporosis
• Rheumatoid arthritis
• Septic arthritis
• Soft tissue trauma (e.g., Labral tear, meniscal tears[14]
• Subchondral fractures[1]

The prognosis for osteonecrosis is often poor regardless of the initial management strategy. Progression of the disease includes persistent pain, debilitation, and destruction of the joint beyond repair. Mont et al.[2]reported that 59% of asymptomatic lesions progressed to symptoms or collapse. AVN of the humeral head, in particular, can be even worse, with as many as 81% of patients progressing to total failure requiring arthroplasty.[8] Therefore once the patient faces the onset of osteonecrosis, there is a high probability that it will continue to advance.

Core decompression and bone grafting can prevent the progression of osteonecrosis of the hip. However, with advanced disease or failure of joint-preserving therapies, total hip arthroplasty is needed but is associated with increased complication rates.[28]

Core decompression and hemiarthroplasty of the shoulder have good outcomes in treating AVN in the early stages. However, total shoulder arthroplasty has higher complication rates. Total shoulder arthroplasties are indicated for end-stage AVN but put the patient more at risk for complications postoperatively.[15]

In Preiser and Kienbock's disease, the initial stages of AVN are treated with immobilization, but eventual surgical intervention is usually indicated.[12][17] Surgical repair of the talus in AVN management tends to have significantly better outcomes in younger patients.[10]

Common postoperative complications for osteonecrosis include surgical site infections, prosthesis malfunctions, and neurovascular compromise.[15] High failure rates occur as the disease continues to progress despite surgical intervention. For example, core decompression failed to prevent disease progression in 90% of patients treated for AVN of the hip.[8] In Kienbock's disease, not taking into account the patient's unique anatomy when performing an osteotomy of the radius can result in excessive positive ulnar variance and ulnar pain postoperatively.[17]

Patient comorbidities greatly influence complication rates as well. For example, patients with sickle cell disease undergoing total joint replacement for AVN had more extended hospital stays, increased likelihood of acute kidney injury, implant failure, pulmonary embolism, deep vein thrombosis, myocardial infarction, and an overall higher mortality rate.[8]

Osteonecrosis often starts even before a patient experiences symptoms. It typically progresses to end-stage disease if left untreated. Symptoms vary, but patients with late-stage disease usually have severe pain, debilitation, and even joint collapse.[1] 

Patient presentation of this disease is highly variable, so it is essential to reduce your risk factors. Ways to decrease risks include avoiding excessive alcohol consumption, no tobacco use, and tapering corticosteroids to the lowest necessary dose. Other lifestyle modifications like eating a healthy diet and maintaining an appropriate weight minimize joint damage. For manual laborers, consider avoiding repetitive activities that place strain on your joints. If possible, laborers should take regular breaks. Lastly, be proactive. Since patients with early-stage often do not have symptoms, they should seek periodic well-being evaluations by their primary care physician.[1]

There are several identified risk factors for osteonecrosis, but the exact pathogenesis remains unestablished. More likely a combination of different factors and conditions leads to the destruction of bone cells.

Intervention depends on the phase of disease progression and varies from preservation procedures to more definitive salvage operations.

Treatment of early-stage disease reports better results although this may be difficult to achieve as osteonecrosis is often asymptomatic in its early stages.

The majority of non-traumatic cases are associated with glucocorticoid use.[2]

Osteonecrosis frequently poses a diagnostic dilemma to orthopedic surgeons. There are several risk factors outlined in the literature yet the exact pathophysiology is not fully understood. Diagnostic difficulty frequently results in delayed presentation of advanced cases of the disease, which often prevents the joint from being salvaged and increases patient morbidity. While an orthopedic surgeon is almost always involved in the care of patients with osteonecrosis, it is important to educate healthcare professionals who encounter these patients at the hospital front door such as general practitioners, emergency department physicians, nurses, and physiotherapists.