FHO (femoral head ostectomy) is a surgery that removes the ball portion of your cat’s hip joint to eliminate pain from a damaged or diseased hip. The remaining bone and surrounding muscles eventually form a “false joint” made of scar tissue, which restores functional mobility without the bone-on-bone grinding that caused pain in the first place.
It’s classified as a salvage procedure, meaning it’s typically performed when the hip joint can’t be repaired or preserved. For many cat owners, it’s a practical and affordable path to getting their cat moving comfortably again.
Why Cats Need FHO Surgery
The most common reason cats undergo FHO is a fracture of the femoral head, the ball-shaped top of the thighbone. This type of break, called a femoral capital physeal fracture, is especially common in younger cats whose growth plates haven’t fully closed. A fall, a car accident, or even a jump from a height can snap the femoral head off its neck.
Other conditions that lead to FHO include hip dislocations that can’t be held in place, fractures of the hip socket itself, and severe arthritis that doesn’t respond to pain medication or weight management. Vets generally consider FHO when nonsurgical options like anti-inflammatory drugs, rest, and weight loss haven’t resolved the limping or pain.
What the Surgeon Actually Does
The surgeon makes an incision near the hip, opens the joint capsule, and cuts through the ligament that anchors the femoral head inside the socket. Then, using a surgical saw, they cut through the femoral neck and remove the entire ball of the joint. What’s left is an empty hip socket and the shaft of the thighbone, with no bony contact between them.
There are two main surgical approaches. The more traditional route goes in from the side and top of the hip. A newer ventral (bottom-side) approach spares more of the muscles and soft tissue around the top of the hip, gives the surgeon a better view of key landmarks on the bone, and makes it easier to operate on both hips in a single session if needed. Both approaches produce similar outcomes for the cat.
How a “False Joint” Forms
After the femoral head is removed, the leg muscles hold the thighbone roughly in position near the empty socket. Over the following weeks, scar tissue gradually fills the gap between the socket and the cut end of the femur. This fibrous cushion becomes what vets call a pseudoarthrosis, or false joint. It’s not a normal hip. There’s no ball clicking smoothly into a socket. But the scar tissue padding, combined with the surrounding muscle, allows the leg to swing, bear weight, and move without bone grinding painfully against bone.
Keeping your cat gently active during recovery is important because it prevents that scar tissue from forming too tightly, which would limit flexibility. A false joint that develops while the cat is moving tends to allow a better range of motion than one that forms while the cat is immobile.
Recovery and Rehabilitation
Most cats begin touching the foot of the operated leg to the ground within the first week or two, though they won’t put real weight on it yet. Active use of the limb generally takes over a month, and full rehabilitation commonly stretches to six months or longer. Cats tend to recover more readily than large dogs because they’re lighter, which puts less mechanical stress on the healing tissues.
During recovery, gentle encouragement to use the leg matters more than strict rest. Short walks around the house, light play, and controlled movement help the false joint develop properly. Your vet may recommend physical therapy exercises like gentle range-of-motion stretches or controlled leash walks. The goal is consistent, low-intensity movement rather than sudden bursts of activity.
Cats that are lean, active, and have good muscle tone before surgery tend to recover best. Obesity makes recovery significantly harder because the extra weight strains the developing false joint and the muscles that now do the hip’s structural work. If your cat is overweight, even modest weight loss before or after surgery can improve the outcome.
What Outcomes Look Like
Most cat owners report that their pet returns to comfortable daily activity after FHO. The surgery reliably eliminates the sharp pain of a broken or arthritic hip, and cats are generally able to jump, climb, and move around the house. One study using computerized gait analysis, radiographs, and orthopedic exams on a combined group of dogs and cats rated functional results as good in 38% of animals, satisfactory in 20%, and poor in 42%.
Those numbers deserve context. “Good” and “satisfactory” in a clinical gait study are measured against a perfectly normal hip, a standard that even a pain-free FHO patient won’t meet. Owner satisfaction tends to run higher than objective gait scores because what most owners care about is whether their cat moves without pain, not whether the gait is biomechanically perfect.
That said, FHO does come with lasting changes. The operated leg is slightly shorter because the ball of the joint is gone, and the thigh muscles on that side typically remain somewhat smaller than the other leg. Studies in animals post-FHO consistently show reduced hip extension and decreased weight-bearing on the operated limb even when owners consider the result excellent. Some degree of muscle atrophy and mildly altered gait are the norm rather than the exception.
FHO Compared to Total Hip Replacement
Total hip replacement (THR) is the other major surgical option for a severely damaged hip. It replaces the ball and socket with artificial components, restoring near-normal joint mechanics. Animals that receive a total hip replacement bear significantly more weight on the operated leg than those that undergo FHO, and they return closer to normal function overall.
So why doesn’t every cat get a hip replacement? Cost is the biggest factor. THR is substantially more expensive, requires specialized equipment, and is only performed at certain referral hospitals. It also demands a specific implant size, which limits eligibility for very small cats. FHO can be performed by most veterinary surgeons, costs less, and doesn’t rely on an implant that could loosen or fail over time.
Veterinary surgeons generally consider total hip replacement the superior procedure when it’s feasible, and recommend FHO when hip replacement isn’t an option due to the cat’s size, the owner’s budget, or other health factors. For a cat that primarily needs pain relief and household-level mobility, FHO delivers meaningful improvement at a fraction of the cost.
Risks and Potential Complications
FHO is considered a relatively safe procedure, but no surgery is without risk. The main long-term effects are the ones already described: some degree of limb shortening, thigh muscle loss on the operated side, and a reduced range of motion in the hip compared to normal. These changes are inherent to the procedure rather than complications, since removing the femoral head permanently alters the joint’s structure.
True surgical complications are less common but can include infection at the incision site, damage to nearby nerves or blood vessels during the operation, or a rough bone edge left at the cut site that causes persistent discomfort. If bone fragments or sharp edges remain, a second surgery to smooth the area may be needed. Persistent lameness that doesn’t improve over several months can also occur, particularly in cats that are sedentary or overweight during the recovery period.
Older cats and those with other health conditions face higher surgical risk from anesthesia and slower tissue healing, though age alone doesn’t disqualify a cat from the procedure. The strongest predictors of a good outcome are lean body weight, adequate muscle mass, and consistent post-surgical rehabilitation.