CONDITION
Avascular Necrosis of the Femoral Head
Avascular necrosis of the femoral head is a condition in which the blood supply to the ball of the hip joint is disrupted, causing the bone tissue to die and the joint surface to collapse. It tends to affect young dogs of small and toy breeds, often appearing between four and eleven months of age, and typically involves only one hip. Owners most commonly notice a gradual onset of limping on one hind leg, with the dog becoming reluctant to bear weight or use the affected limb. The lameness may worsen over weeks to months as the bone deteriorates, and the dog may hold the leg up or show discomfort when the hip is moved. This page explores the signals that may be observed, what is happening beneath the surface in the bone and joint, how the condition is investigated through examination and imaging, and the approaches that exist to manage it.
Why this matters now
This condition tends to appear in young dogs of small and toy breeds, typically during a narrow window between four and eleven months of age, with many cases becoming apparent between five and eight months. Terrier breeds, along with Chihuahuas, Poodles, Pomeranians, and Bichon Frisés, are among the groups in which the condition is seen more frequently. A hereditary component has been suggested in some breeds, though the precise cause of the disrupted blood supply remains unknown.
The lameness often begins subtly and worsens gradually over a period of weeks to months as the bone tissue dies and the joint surface deteriorates. In many cases, the dog progresses from mild intermittent limping to a point where little or no weight is placed on the affected leg. Muscle wasting in the affected limb may become noticeable as the dog favours the other leg, and the joint surface may develop an irregular shape that no longer fits smoothly within the socket.
Signals & patterns
Early signals
Subtle hind-leg limp
The dog may begin to favour one hind leg, showing a slight unevenness in gait that comes and goes. This early lameness can be easy to miss, particularly in active young dogs who may still run and play.
Reluctance to bear full weight
The dog may shift weight away from the affected leg when standing or move more cautiously, particularly after rest or when rising from lying down. The reluctance can be subtle at first, appearing as a brief hesitation or a slightly shortened stride.
Stiffness after rest
The leg may appear stiffer or less fluid in movement after the dog has been lying down, improving somewhat with gentle activity. This pattern reflects the discomfort within the hip joint as it begins to change.
Reduced willingness to jump or climb
Activities that load the hip joint, such as jumping onto furniture or climbing stairs, may become less appealing. The dog may pause before attempting these movements or choose to avoid them altogether.
Later signals
Persistent non-weight-bearing lameness
As the joint surface collapses, the dog may hold the leg up entirely, refusing to place the paw on the ground even when walking slowly. This reflects significant deterioration of the bone and progressive pain within the joint.
Visible muscle wasting
The muscles of the affected thigh and hip may become noticeably smaller compared to the opposite leg, a consequence of prolonged disuse. The limb may also appear shorter when the dog is standing.
Audible or palpable joint changes
The hip may produce a grating sensation or sound when moved, caused by the roughened, irregular surfaces of the damaged joint rubbing together. The dog may show clear discomfort or resistance when the hip is handled or manipulated.
Click to read about the biological mechanisms
How this is usually investigated
The investigation typically begins with a detailed history of the lameness—when it started, how it has progressed, and whether the dog shows pain when the hip is handled—followed by careful observation of gait and weight-bearing at rest and in motion. Physical examination of the hip often reveals discomfort when the joint is manipulated, reduced range of motion, and muscle wasting in the affected limb compared to the other side. Radiography is usually the primary tool for confirming the diagnosis, though the timing and findings can vary depending on how far the disease has progressed.
Physical examination
Radiography
Magnetic resonance imaging (MRI)
Computed tomography (CT)
Options & trade-offs
Management is usually tailored to the individual dog, taking into account the severity of lameness, the degree of joint damage, the dog's size and activity level, and what the household can sustain over time. Some dogs are managed with pain relief and reduced activity whilst the bone remodels, though most cases eventually require surgical intervention to relieve pain and restore function. Different approaches suit different dogs and different owners, and the choice often involves weighing the immediacy of improvement against the complexity and cost of treatment.
Femoral head and neck ostectomy
The damaged ball of the hip joint is surgically removed, along with a portion of the femoral neck, creating a false joint in which the femur is stabilised by surrounding muscles and scar tissue. Over weeks to months, a fibrous pseudo-joint forms that can bear weight and allow reasonable function, particularly in small dogs. Physiotherapy and controlled activity in the weeks after surgery help encourage muscle development and mobility.
Trade-offs: The procedure is well-established and can relieve pain effectively, with owner satisfaction reported in the range of eighty-three to ninety-six per cent in published studies. Functional outcomes can be more variable; small dogs under around twenty kilograms tend to regain good use of the limb, whilst larger dogs may experience persistent lameness or reduced muscle mass. Some degree of limb-length discrepancy and gait asymmetry may remain long-term.
Total hip replacement
The diseased femoral head and damaged acetabulum are replaced with artificial components—a metal or ceramic ball and a polyethylene or metal cup—that restore a smooth, stable joint surface. The procedure aims to return the limb to near-normal function and is typically performed by a specialist orthopaedic surgeon.
Trade-offs: Total hip replacement can offer more complete restoration of limb function than femoral head ostectomy, particularly in young, active dogs where long-term athleticism matters. The surgery is more complex, carries risks including infection, implant loosening, and dislocation, and requires a referral centre with specialist expertise. It is also considerably more expensive, and implant options for very small dogs may be limited.
Conservative management with analgesia and activity modification
Pain relief—often using non-steroidal anti-inflammatory drugs—is combined with restricted exercise and physiotherapy to reduce discomfort and maintain muscle tone whilst the bone attempts to remodel. The approach may be chosen in very early cases, in dogs with mild clinical signs, or when surgical options are declined.
Trade-offs: Conservative management may provide temporary relief and can occasionally allow improvement in dogs with minimal collapse, but the underlying bone damage usually progresses, and most dogs eventually develop persistent lameness and pain that limits quality of life. This approach is less likely to restore full function and is often a bridge to surgery rather than a definitive solution.
Physiotherapy and rehabilitation
Structured exercise programmes, hydrotherapy, massage, and passive range-of-motion exercises are used to maintain or rebuild muscle mass, preserve joint mobility, and support weight-bearing. Rehabilitation is often combined with other treatments, particularly after femoral head ostectomy, to optimise recovery.
Trade-offs: Physiotherapy can improve outcomes when used alongside surgical or medical management, helping dogs regain strength and coordination more quickly. It requires regular sessions, owner commitment, and access to a trained practitioner. Used alone, without addressing the damaged joint, it cannot halt disease progression or relieve pain in moderate to severe cases.
Common misconceptions
"If one hip is affected, the other will inevitably develop the same problem."
Avascular necrosis most commonly involves only one hip. Whilst the condition does appear more often in certain small and toy breeds, and a hereditary component has been suggested, bilateral disease occurs in around twelve to seventeen per cent of cases—roughly one in six to eight affected dogs. The majority of dogs will not develop disease in the second hip.
"Removing the ball of the hip joint will leave the dog unable to walk normally."
Femoral head and neck ostectomy creates a false joint stabilised by muscle and scar tissue, and many small dogs regain functional use of the limb after surgery and rehabilitation. Whilst gait may not return to completely normal, and some asymmetry or reduced muscle bulk may persist, most dogs are able to walk, run, and play with acceptable comfort. Outcomes tend to be better in smaller, lighter dogs.
"The condition will resolve on its own if the dog rests for a few weeks."
Avascular necrosis is a progressive disease in which the bone has already lost its blood supply and begun to die. Rest and restricted activity may reduce discomfort temporarily, but the underlying structural damage to the femoral head continues, and the joint surface typically deteriorates further over time. Most dogs eventually require surgical intervention to relieve pain and restore meaningful function.
Related conditions
Arthritis in Cats
Osteoarthritis in cats often develops in the hip joint and can cause similar patterns of hind limb lameness and reduced mobility, though in cats it tends to appear in older animals rather than during growth. Both conditions involve progressive deterioration of the hip joint surface, though the underlying mechanisms differ.
Elbow Dysplasia in Dogs
Elbow dysplasia shares features with avascular necrosis as a developmental orthopaedic condition affecting young, growing dogs, though it causes forelimb rather than hind limb lameness. Both conditions involve abnormal bone development during the growth period and can lead to early-onset osteoarthritis if left unmanaged.
Coxofemoral Subluxation
Coxofemoral subluxation describes a partial displacement of the hip joint that can occur alongside or as a consequence of femoral head deterioration. In some cases, the weakened bone and joint surface changes seen in avascular necrosis may contribute to instability of the hip.
Degenerative Myelopathy
Degenerative myelopathy can present with progressive hind limb weakness that may initially be mistaken for a joint problem such as hip disease. Unlike avascular necrosis, which causes pain and lameness localised to one hip, degenerative myelopathy typically produces symmetrical weakness without localised joint pain and affects older dogs.
Understanding how the condition has been progressing, what degree of function the dog currently has, and what expectations exist for activity and mobility over the coming months can help shape conversations about the timing and type of intervention. For dogs in which surgery is being considered, discussing the differences between femoral head ostectomy and total hip replacement—including what each involves, the anticipated recovery, and the longer-term functional outlook—can clarify which approach may be more suitable. In dogs where surgery is not pursued, understanding what realistic goals exist for comfort and mobility with medical management alone can inform day-to-day decisions about activity and analgesia.
Last reviewed: 12 September 2026 · Dr Alastair Greenway MRCVS