Common Complications After FHO Surgery in Dogs

FHO surgery is generally safe and well-tolerated, but complications do occur. Knowing what to watch for, how to recognize a problem early, and how serious each type of complication actually is helps you respond appropriately without either missing a real problem or panicking over normal post-surgical healing.

Quick answer: The most common FHO complications are muscle atrophy from insufficient rehabilitation, reduced range of motion from excessive scar tissue, and persistent lameness. Less common but important complications include surgical site infection and sciatic nerve irritation. Major complications requiring surgical intervention occur in approximately 13% of cases, based on the JAVMA 2025 study. Most complications are manageable with early recognition and appropriate response.

Key takeaways

• Muscle atrophy is the most preventable complication: it results from inadequate rehabilitation.
• Persistent lameness beyond 3 to 4 months should be evaluated; it may indicate inadequate muscle development or residual bone contact.
• Infection is uncommon but serious: spreading redness, discharge, or fever require same-day vet contact.
• Sciatic nerve injury is rare but produces a distinctive knuckling or dragging of the paw.
• Bone spur development can cause recurring bone-on-bone contact and may require revision surgery.
• JAVMA 2025: 33.8% minor complications, 13.2% major, 4.4% surgical revision in 68 FHO cases.

Published complication rates: what the research shows

The JAVMA 2025 retrospective study of 68 FHO cases across four hospitals provides the most current complication data:

• Minor complications (no additional surgery or medications required): 33.8% of cases, including persistent lameness not requiring additional pain medication (17 cases), incisional irritation (2), anxiety (2), seroma (1), and persistent resistance to limb extension (1)
• Major complications requiring intervention: 13.2% of cases, including GI upset (3 cases), infection (1), persistent lameness requiring additional pain medications (2), and surgical revision (3)
• Surgical revision required: 4.4% of cases; all three revision cases involved bony contact from bone spur development

Top Dog Health summarizes the most common complications across the literature: "decreased range of motion and mobility in the leg, muscle atrophy, loss of function, limb shortening, and infection."

Complication 1: Muscle atrophy

What it is

Muscle atrophy is the loss of muscle mass in the thigh and hip region of the operated leg due to reduced use. Some degree of muscle atrophy before surgery (from the pain-related period) and immediately after surgery (from rest) is expected. The complication is when muscle loss is excessive or fails to reverse with rehabilitation.

Why it happens

• Inadequate or delayed rehabilitation after surgery
• Insufficient pain control preventing the dog from using the leg
• Owner non-compliance with exercise protocol
• Pre-existing severe atrophy before surgery that wasn't addressed

What you'll see

• Visible asymmetry: operated thigh is noticeably smaller or thinner than the other side
• The dog consistently avoids the leg even after the expected recovery period
• Reduced confidence using the leg on uneven ground or during transitions

What to do

Muscle atrophy after FHO responds to structured rehabilitation. Begin or intensify the following:

• Controlled leash walking: slow, on flat ground, at a pace that encourages the dog to bear weight on the leg
• Sit-to-stands: the most targeted exercise for the hip extensors and quadriceps
• Hydrotherapy (underwater treadmill): rebuilds muscle without joint loading
• Consistent daily effort for several weeks

If significant atrophy persists despite 4 to 6 weeks of consistent rehabilitation, consult a certified canine rehabilitation therapist for a structured program.

For how rehabilitation directly addresses and prevents muscle atrophy, see post-op care that reduces complications.

Complication 2: Reduced range of motion / scar tissue stiffness

What it is

Scar tissue naturally forms as the false joint develops. If this scar tissue forms excessively or in a restrictive pattern, it can limit how far the hip can flex and extend. The result is a stiff gait, difficulty sitting fully, and reduced hip extension during walking.

Why it happens

• Insufficient movement during the early recovery phase
• The false joint forms tightly due to inadequate early range-of-motion exercises
• Large dogs may be more prone due to the greater forces involved in false joint formation

What you'll see

• The dog's operated leg appears stiff during walking
• The dog has trouble sitting squarely
• On observation, the hip doesn't extend fully during trotting
• Resistance when the leg is gently extended

What to do

• Passive range-of-motion (PROM) exercises should begin within the first 1 to 3 days post-surgery to prevent this
• If stiffness develops, intensive PROM, gentle stretching, and hydrotherapy are the primary interventions
• Laser therapy at a rehabilitation facility can help reduce scar tissue density
• If range of motion stays limited beyond 8 to 10 weeks, a referral to a certified canine rehabilitation therapist is appropriate

Complication 3: Persistent lameness

What it is

Mild limping in the first 2 to 4 weeks is expected. Persistent lameness beyond 4 to 6 months, or lameness that worsens after a period of improvement, is a complication.

Causes

• Inadequate muscle development (the most common cause)
• Residual bone contact from incomplete femoral neck removal
• Bone spur development causing secondary bone contact (as seen in the JAVMA 2025 revision cases)
• Pain from adjacent joint disease developing due to compensation patterns

What you'll see

• Consistent limping or shortened stride on the operated leg beyond the expected recovery period
• Worsening lameness after a period of apparent improvement
• The dog avoids loading the operated leg in activities like going upstairs

What to do

• A vet assessment with radiographs is the appropriate response to persistent lameness
• Radiographs can identify whether bone contact is occurring from residual neck bone or bone spur formation
• If no bony issue is identified, intensify rehabilitation targeting the hip extensors
• If bone contact is confirmed, surgical revision may be needed (as in the 4.4% of JAVMA cases)

For how complications affect the recovery timeline, see how complications affect the recovery timeline.

Complication 4: Surgical site infection

What it is

Infection at the FHO incision site. This is an uncommon complication but requires prompt attention when it occurs.

Why it happens

• Licking the incision (most common cause): introduces bacteria directly into the healing wound
• Environmental contamination of the incision site (walking through dirty water, rolling in grass)
• Systemic factors reducing immune response

What you'll see

Early infection signs:

• Redness extending beyond the incision edges
• Increased heat around the incision
• Yellow, green, or creamy discharge from the incision
• Foul odor from the wound or bandage
• The dog's interest in the incision increases

Systemic signs of deeper infection:

• Fever
• Lethargy
• Reduced appetite
• Marked worsening of lameness

What to do

Contact your vet the same day if you see any of these signs. Superficial infection is treated with antibiotics and local wound care. Deeper infections may require more intensive treatment. Do not wait to see if it resolves on its own.

Prevention: The E-collar must be worn at all times when you can't directly supervise your dog. This is the single most effective infection prevention step in your control.

Complication 5: Sciatic nerve injury

What it is

The sciatic nerve runs near the hip joint and can be affected during or after FHO surgery. Sciatic nerve injury is rare but serious. PetMD notes: "Other risks include infection of the surgical site and damage to the sciatic nerve, which runs near the hip joint."

Why it happens

• Surgical trauma to the nerve during the procedure (uncommon with experienced surgeons)
• Post-operative inflammation or swelling pressing on the nerve
• Scar tissue formation affecting nerve function during healing

What you'll see

• Knuckling: the dog places the top of the paw on the ground rather than the pads (the paw is folded under)
• Dragging: the dog drags the paw during walking
• Reduced withdrawal reflex: reduced or absent response when the paw is pinched
• Muscle weakness: more pronounced than expected for the recovery phase

What to do

Sciatic nerve signs warrant same-day veterinary assessment. Mild cases (from post-operative inflammation) often resolve with time and anti-inflammatory medication. More significant injuries require neurological assessment. Protective paw boots can prevent abrasion to a knuckling limb while recovery is ongoing.

Complication 6: Seroma

What it is

A seroma is a pocket of sterile fluid that accumulates under the skin near the incision. It appears as a soft, fluctuating swelling beneath the incision site.

Why it happens

• Normal response to surgical tissue disruption
• Excessive activity in the early recovery period increasing fluid production
• Inadequate rest

What you'll see

• Soft, puffy swelling near or below the incision
• Not particularly hot or painful to the touch
• No discharge or odor (distinguishes it from infection)
• Typically appears in the first 1 to 2 weeks

What to do

Most seromas are monitored rather than immediately treated. Strict rest reduces fluid production. Contact your vet to confirm the diagnosis. If the seroma is large, under significant tension, or if you're unsure whether it's a seroma or infection, veterinary assessment is appropriate.

Complication 7: Gastrointestinal upset

The JAVMA 2025 study found GI upset as the most common major complication (3 of 9 major complication cases). Post-surgical GI upset in dogs is typically related to:

• NSAIDs given without food (can irritate the gastric mucosa)
• Anesthesia effects on gut motility
• Stress-related gut changes in the perioperative period

Prevention: Always give NSAIDs with food. A bland diet for the first few days post-surgery reduces GI stress. If vomiting or diarrhea occurs after starting post-operative medications, contact your vet: a different medication protocol or temporary medication adjustment may be needed.

For how complications compare to normal recovery expectations, see normal expectations vs complications.

Complication recognition: quick reference

For guidance on cases where complication risk is considered in the recommendation framework, see cases where complication risk is considered.

For how post-surgical care directly reduces complication risk, see how complications affect success rates.

Frequently asked questions

My dog is limping at week 6. Is this a complication?

Some limping at week 6 is still within the expected recovery range, particularly in large breeds or dogs with pre-existing muscle atrophy. If the lameness is clearly improving week over week, it may not be a complication. If it has plateaued or worsened, a vet assessment is appropriate.

Is it normal for the operated area to feel warm for several weeks?

Some warmth at the surgical site in the first 1 to 2 weeks is normal tissue healing. Warmth that persists beyond 2 to 3 weeks, or that increases after a period of improvement, is worth checking. This could indicate ongoing inflammation, infection, or other issues.

My dog's paw seems to fold under when walking. Should I be worried?

Yes, this warrants same-day veterinary attention. Knuckling (paw folding under) can indicate sciatic nerve involvement. It can also reflect neurological problems unrelated to the surgery. Either way, it needs professional evaluation.

Complications after FHO are real, and some are serious. But most are recognizable early, and most respond well to prompt attention. The combination of daily incision monitoring, consistent rehabilitation, adequate pain control, and E-collar compliance addresses the majority of complication risk directly. Know what to watch for, and don't hesitate to contact your vet when something looks wrong.

Resources

• JAVMA. Acute vs. chronic coxofemoral disease: FHO complications and outcomes. avmajournals.avma.org
• Top Dog Health. Femoral Head Osteotomy for Dogs. topdoghealth.com
• PetMD. Femoral Head Ostectomy in Dogs and Cats. petmd.com