Bilateral AVN: When Both Hips Are Affected — What It Means and What to Do

When AVN is caused by steroids, alcohol, sickle cell disease, or systemic conditions — it is not a local problem in one hip. The cause acts on both femoral heads simultaneously. Both hips share the same blood supply risk factors, the same circulating steroid levels, the same metabolic imbalances. The fact that one hip becomes symptomatic before the other does not mean only one hip is affected — it means one hip has progressed faster.

The published data: in steroid-induced AVN, bilateral involvement is documented in 50-80% of cases across multiple large series. In alcohol-related AVN, bilateral rates are similarly high. In traumatic AVN (caused by a specific injury to one hip — fracture, dislocation), bilateral is less common because the cause was localised.

Why the second hip is often found later: the symptomatic hip dominates the patient's attention. The patient limps, favours the painful side, and unknowingly offloads the less painful hip — which may have Grade 1 or early Grade 2 AVN that is not yet causing significant pain. When that patient is eventually told "get both hips imaged," the second hip is often found to be at an earlier but real stage of AVN.

The clinical implication of this pattern: every patient diagnosed with AVN from a systemic cause (steroids, alcohol, sickle cell) should have both hips imaged at diagnosis — not just the symptomatic one. Waiting until the second hip becomes painful means losing the window for early intervention on that side.

What asymmetry looks like: it is common for bilateral AVN to present asymmetrically — one hip at Grade 2, the other at Grade 1 or early Grade 2. Less commonly, both are at the same stage. Occasionally, one hip has already collapsed (Grade 4) when the other is found at Grade 2 — particularly in patients who delayed the diagnosis of the first hip for months or years.

Single-hip AVN allows a compensation strategy: the patient limps, offloads the painful hip, and uses the other leg as the "good" leg. This compensation is not ideal for the good leg, but it works as a short-term strategy.

Bilateral AVN removes this option. When both hips are compromised, there is no truly good leg to compensate with. Walking becomes significantly more difficult — not just more painful. Patients often report that bilateral AVN changes their gait entirely: shuffling, reduced stride length, inability to negotiate stairs normally, and difficulty rising from chairs and low surfaces.

The mechanical risk of favouring one side with bilateral AVN: when one hip is more painful than the other, patients instinctively load the less painful hip more heavily. If the less painful hip has Grade 2 AVN, this increased loading can accelerate its progression — potentially pushing it toward collapse faster than it would have progressed without the extra load. This is a real risk, not a theoretical one.

Walking support is not optional in bilateral AVN: bilateral AVN almost always requires walking support — crutches or a walker — during the treatment phase. This is not a concession to pain tolerance; it is a structural protection measure for both femoral heads. Partial weight bearing (taking some weight through the crutches on both sides) is the appropriate goal, not complete non-weight bearing (which is extremely difficult to achieve bilaterally and is not necessary in most Grade 1-2 cases).

Swimming and water-based movement: for patients with bilateral AVN, water exercise is often the most practical form of therapeutic movement. In water, body weight is largely supported, allowing the hip muscles to be active without loading the femoral heads. If there is any pool access, water walking or gentle swimming should be the primary exercise modality in bilateral Grade 2-3 AVN.

Bilateral AVN does not mean bilateral surgery at the same time. This is a critical clarification that many patients do not receive.

How bilateral management is actually sequenced:

If both hips are at Grade 1-2: non-surgical management is the goal for both. The treatment is the same as for unilateral Grade 1-2 — address the systemic cause, protect both hips from excessive loading, support circulation, and monitor both hips with repeat MRI at 6 months. The bilateral nature makes the monitoring more important, not less.

If one hip is Grade 2 and the other is Grade 3A: conservative management continues for the Grade 2 hip. The Grade 3A hip is the focus of more intensive monitoring — whether collapse is occurring or whether the Grade 3A is stable. The decision for the Grade 3A hip needs to be individualised.

If one hip is Grade 3B-4 and the other is Grade 1-2: the collapsed hip may need surgical discussion. The other hip — crucially — should be managed conservatively and protected. Surgery on one hip does not mean surgery on both simultaneously.

If both hips are Grade 3-4: this is the most complex scenario. Bilateral hip replacement is possible but is not done simultaneously in most centres — the rehabilitation from two simultaneous hip replacements is extremely demanding. Staged replacement (one hip at a time, 6-12 weeks apart) is the standard approach when both hips ultimately need replacement.

The honest picture of bilateral surgical outcomes: patients who need bilateral hip replacement ultimately do well in most cases — the function after bilateral hip replacement is better than the function with bilateral collapsed AVN. But the rehabilitation is longer, the early post-operative phase is more demanding, and the patient needs strong family support and dedicated physiotherapy. These are not reasons to avoid surgery when it is the right decision — they are reasons to plan it carefully and with realistic expectations.

When you have bilateral AVN, monitoring cannot focus on one hip and ignore the other. The monitoring protocol needs to cover both.

Repeat MRI: both hips should be imaged together on repeat MRI. This is logistically simple — a bilateral hip MRI is a single scan that images both femoral heads. Request this explicitly: "bilateral hip MRI with comparison to previous study." Do not do unilateral MRI alternately — you need simultaneous comparison of both.

What to look for on the less symptomatic side: the less painful hip is not necessarily the "safer" hip. On MRI, look for: increase in lesion size (percentage of femoral head), appearance of a crescent sign (subchondral fracture line — this is the critical change), and new bone marrow oedema. Any of these on the previously "better" hip signals that it is progressing and needs management escalation.

Pain as a monitoring signal — useful but unreliable: changes in which hip is more painful, or new pain in a previously comfortable hip, are useful warning signals. However, Grade 2-3 AVN can progress significantly on MRI before pain changes are noticed — particularly if the patient is already compensating with walking support. MRI is more reliable than pain level as a monitoring signal.

Frequency: in bilateral Grade 1-2, repeat MRI at 6 months after starting treatment. If stable — every 6-12 months thereafter. If either hip shows progression — more frequent monitoring and immediate management discussion.

The simple rule: if bilateral AVN is your diagnosis — never attend a follow-up appointment without updated imaging of both hips. One hip's stability does not guarantee the other's.

Managing bilateral AVN requires changes that go beyond the single-hip case. These are the practical adjustments that make a meaningful difference.

Sitting surfaces matter more: low sofas, floor sitting, and chairs without armrests create significant hip flexion and make rising difficult in bilateral AVN. The patient needs a firm chair with armrests at a height where the hips are at 90 degrees or slightly above — this minimises the compressive load on the femoral heads during sitting and makes standing easier.

Toilet height: low toilets require a large range of hip flexion and significant compressive load when rising. A raised toilet seat (readily available in medical supply shops) is often essential in bilateral Grade 2-3 AVN. This is not a "comfort" measure — it is a structural protection measure.

Sleeping: a pillow between the knees in a side-lying position prevents the top hip from adducting (crossing over), which reduces shear stress on the femoral head. In bilateral AVN, alternating which side you sleep on — rather than always lying on the more comfortable side — distributes the loading more evenly.

Car travel: entering and exiting a car requires significant hip range of motion and is a common pain trigger in bilateral AVN. Seat height matters — higher vehicles (SUVs) are significantly easier than low cars. When entering, lead with the more stable hip. When exiting, rotate the body as a unit rather than twisting one hip at a time.

Work and occupation: if your work requires prolonged standing (more than 2-3 hours continuously) or involves climbing, heavy lifting, or walking on uneven surfaces — this needs to be modified during the active treatment phase. This is a medical necessity, not a preference. Documentation from the treating doctor supporting occupational modification is legitimate and important.

Emotional impact: bilateral AVN has a significant psychological burden — loss of mobility, uncertainty about surgery, fear of permanent disability. This is real and should be acknowledged. Support from family, realistic expectation-setting from the treating doctor, and connection with others managing similar conditions are all meaningful. Unrealistic optimism ("both hips will be fully cured") is as harmful as unnecessary pessimism.

The outcome in bilateral AVN depends heavily on the stage at which both hips are caught and how consistently management is implemented. Here is the honest picture.

Best case — both hips at Grade 1-2, caught early, systemic cause removed: stabilisation of both femoral heads is achievable. Documented cases exist of bilateral Grade 2 AVN managed without surgery, with stable or improving MRI findings over years, and return to functional daily activity. This is not guaranteed, but it is the realistic goal of early-stage bilateral management.

Middle case — one hip at Grade 2-3, other at Grade 1-2: the Grade 2-3 hip carries more risk. Conservative management continues for both, but the Grade 2-3 side requires more frequent monitoring. The Grade 1-2 side is the priority for protecting — preventing its progression is the most important near-term goal.

Difficult case — both hips at Grade 3-4 or one already collapsed: surgical planning becomes the central conversation. Bilateral hip replacement, staged appropriately, is a real and functional solution. Patients with bilateral hip replacement can return to walking without aids, climb stairs, and live independently — but the recovery timeline is 9-18 months for full functional restoration after staged bilateral surgery.

What does not change the prognosis: the cause of the AVN (steroids, alcohol, or other) does not affect the outcome once the cause is removed. A patient who received COVID steroids and develops Grade 2 bilateral AVN has the same prognosis as any other Grade 2 bilateral AVN patient — provided the cause is no longer active. The history does not make the prognosis worse; the current grade does.

The one factor that most determines outcome: how early both hips are found and treated. The asymmetric presentation — one hip painful, the other silent — is the reason bilateral AVN so often presents late on the second side. Proactive bilateral imaging at the time of first hip diagnosis is the single most important step in improving bilateral AVN outcomes.