Bone: the roof of the socket
The upper rim of the socket forms a bony roof over the ball. This is the dorsal acetabular rim. Its shape and coverage help support the ball when your dog puts weight on the leg.
PennHIP-certified veterinarian
Hip dysplasia in dogs
Hip dysplasia means the hip develops with a loose or unstable fit. A hip assessment helps explain your dog’s symptoms and which treatment could help.
Overview
What is hip dysplasia?
The hip is a ball-and-socket joint. The ball is at the top of the thigh bone; the socket is part of the pelvis. In hip dysplasia, they develop with a loose or unstable fit.
Picture the ball as a fist and the socket as a cupped hand. How much the hand covers the fist helps explain how the socket supports the ball.
Hip dysplasia often runs in families. Growth and body weight also affect the load on a developing hip. Finding the problem early helps the surgical team plan care while all suitable treatment options can still be considered.
What keeps the hip stable?
The socket’s bony rim, the joint capsule and the inner ligament help hold the ball in place.
Soft tissue: the capsule and ligament
- The joint capsule is a strong sleeve around the hip.
- The ligament of the head of the femur is a short band inside the joint, joining the ball to the socket.
These tissues help hold the ball in place. PennHIP measures how loose the joint is.
The muscles around the hip also help support it during movement. A shallow socket covers less of the ball. Loose soft tissues let it move too far. As a puppy grows, loose movement and uneven forces can also change how the socket develops.
How does damage to the hip occur?
A ball that fits well spreads the force of your dog’s weight across the socket. When the ball slips partly out—a movement called subluxation—a smaller area may carry that load. The rim of the socket, the cartilage and the joint capsule can become strained or damaged.
The loose ball may then move back into the socket, called reduction. Repeated abnormal movement during everyday activity contributes to wear. Over time, the joint may develop bone spurs, scar tissue and a reduced range of motion.
Signs and symptoms
What you might notice
Some puppies are painful while the joint is developing. Other dogs show stiffness or difficulty getting up, climbing stairs, running or jumping later in life. A dog can also have abnormal hips without obvious symptoms.
Which dogs should be assessed?
Ask your vet about early hip screening if you have a large- or giant-breed puppy, especially a German Shepherd, Labrador, Golden Retriever, Rottweiler or Saint Bernard, or a dog with a family history of hip dysplasia.
Any young dog that struggles to get up, repeatedly moves both back legs together in a bunny-hop, avoids exercise, has sore hips or limps on a back leg needs an examination. These signs are not specific to the hips; knee, muscle, spinal and other problems can look similar.
A comfortable puppy can still have loose hips.
When should a puppy be assessed?
Ask about hip screening at your puppy's early vet visits, especially if their breed is at risk. You do not need to wait for a limp.
PennHIP can be performed from 16 weeks of age. Some operations have a short window while the pelvis is growing, so contact the surgical team early to plan the assessment. Do not wait until six months to ask.
Diagnosis
Why does the hip assessment use more than one test?
Dr. Wood first watches your dog move and examines the legs and back. The hip assessment then follows this order, because no single test gives the whole picture:
- PennHIP first: how loose is the joint? These X-rays come before joint manipulation, which can introduce artefacts.
- Separate measurements of socket coverage: how well does the socket cover the ball?
- Ortolani: does the ball slip and return?
These tests need relaxed muscles, so they are done under sedation or general anaesthesia. Sedation makes your dog sleepy; general anaesthesia keeps them asleep.
1. PennHIP: how loose is the hip?
Dr. Wood takes the PennHIP X-rays before manipulating the hips for Ortolani testing, to avoid artefacts that could affect the assessment.
The capsule and inner ligament help hold the ball in the socket. PennHIP measures how far the ball can move away when the muscles are relaxed. This is called passive joint laxity, or looseness. It measures the looseness of the whole joint, rather than testing each tissue separately.
PennHIP requires specific training. Dr. Wood is PennHIP-certified and takes these X-rays as part of your dog’s assessment.
There are three views:
- Hip-extended: with the legs extended, to check the joint's shape and signs of arthritis.
- Compression: with the ball seated in the socket, to check how well they fit.
- Distraction: to show how far the ball can move away from the socket.
The two drawings below show why position matters: a loose hip can look snug when the legs are extended.
See compression and distraction X-rays
These are examples of two PennHIP views. They show different things from the hip-extended view.
How is the distraction view taken?
These simplified drawings explain the two views. They are based on PennHIP's official comparison. Your dog's assessment uses their own X-rays.
The PennHIP report gives each hip a looseness number, called the distraction index (DI). A higher DI generally means a looser joint and a greater risk of arthritis. It is not a percentage chance of arthritis, and it cannot predict exactly when a dog will become painful.
See how the looseness number is measured
The surgeon considers PennHIP results alongside bony coverage, arthritis changes and the hands-on tests below.
Official PennHIP owner questions · PennHIP owner brochure (PDF)
2. Bony coverage: how well does the socket cover the ball?
On an X-ray with the legs extended, Dr. Wood checks the shape of the socket and measures how much of the ball it covers:
- Femoral head coverage (FHC): how much of the ball is covered by the socket, expressed as a percentage.
- Norberg angle: an angle that helps describe how the ball and socket line up.
Dr. Wood also scores signs of osteoarthritis (OA), such as bone spurs. This records damage already present. The surgeon considers it alongside the joint's fit and coverage.
A hip can look well seated with the legs extended and still be loose. PennHIP checks for that looseness.
Why use more than one assessment?
A 2024 study of 30 dogs, with an average age of 5.4 years, found that a hip could look reassuring on an X-ray with the legs extended, yet still show looseness on views taken to measure it. This study did not test an early screening plan in puppies. The socket’s coverage, the joint’s looseness and the examination each give different information.
3. Palpation: does the ball slip and return?
With the muscles relaxed, the surgeon gently tests whether the ball can move out of the socket and whether it returns. These are the Barlow and Ortolani tests.
The surgeon also assesses the angles where the ball slips partly out and goes back in: the subluxation angle and reduction angle. Alongside the X-rays, these help the surgeon judge whether an operation to rotate the socket could help.
See the movement and examination angles
Not feeling a slip during the test does not always rule out hip dysplasia. Arthritis, scar tissue or a ball that cannot return to the socket can limit what the surgeon can feel. No single test or measurement decides the treatment.
Treatment
The options depend on how much growth remains, how loose the hips are and whether the joint is already damaged. An abnormal X-ray does not mean every dog needs surgery.
Dr. Wood recommends treatment based on your dog’s comfort, movement and joint damage, and what you hope they can do. Many dogs benefit from weight control, comfortable regular activity, rehabilitation and veterinary pain relief. These measures help symptoms; they do not rebuild the socket.
FHO or total hip replacement?
Both operations aim to reduce pain, but they leave the hip working in different ways. Compare expected function, recovery and lifetime care.
Comfort and leg function are different questions
Both operations aim to improve comfort. FHO leaves the leg supported by soft tissues; THR creates a new ball-and-socket joint. How the leg carries weight is another part of assessing the result.
Compare lifetime care, not only the operation
Eginton and Gordon-Evans compared the modelled lifetime cost of FHO, THR and care without surgery. Ongoing treatment meant that the difference between the two operations could be smaller than their initial surgery prices suggest.
These findings come from a historical US cost model.
How does the starting age change the comparison?
These ages mean the age when clinical signs begin in the study’s model.
- Ages 1–4: FHO had the lowest lifetime cost. THR cost less than care without surgery.
- Ages 5–7: FHO remained the lowest. Care without surgery cost less than THR.
- Age 8 onward: care without surgery had the lowest modelled cost.
THR was never the lowest-cost option in this model.
This study compared financial costs. It did not measure which treatment gave better comfort, movement or quality of life. Those questions still need an individual assessment.
Other options for puppies and young dogs
These options suit selected growing dogs. Age alone does not decide which operation is suitable.
Guide hip growth (JPS) Ideally 12–16 weeks old
Juvenile pubic symphysiodesis (JPS)
JPS closes a small growth plate in the pelvis. A growth plate is an area where young bones grow. As the rest of the pelvis continues to grow, the sockets rotate to cover more of the balls—like bringing the cupped hands farther around the fists.
It is a time-sensitive option for selected young puppies. Earlier treatment generally produces more correction. Published studies include puppies treated at 12–24 weeks, but the useful window is often narrower: treatment near the late end may provide too little improvement. Do not wait until six months to ask about it.
JPS does not guarantee that arthritis will be prevented, particularly in very loose hips. The surgeon considers how loose the joint is, its shape, any damage already present and how much growth remains.
What did the JPS studies show?
Dueland and colleagues studied 33 treated puppies and six controls. Earlier treatment, particularly at 12–16 weeks, produced greater changes in hip shape. The treated dogs' acetabular angle increased by an average of 16° at one year and 19° at two years; controls changed by about 3° and 2°. These are changes in a specific angle, not a guaranteed gain in coverage for every puppy.
Dogs whose hips were mildly to moderately loose at the start did better than those with very loose hips. Arthritis generally progressed in the very loose group despite treatment. Follow-up and small subgroup sizes limit predictions for an individual dog.
Rotate the socket (DPO/TPO) Ideally before 8–10 months old
Rotating the socket: DPO or TPO
If the ball can still be put back into the socket and the hip has little or no established arthritis, a double or triple pelvic osteotomy (DPO/TPO) may be an option. Controlled cuts allow the socket to rotate over the ball. A plate holds the new position while the bone heals.
These procedures are usually considered while a dog is still growing, ideally before about 8–10 months of age. Age alone does not decide this. The surgeon also assesses the cartilage, the socket’s shape, whether the ball can return to the socket, and any arthritis. Selected older dogs may still be candidates.
See how turning the socket changes coverage
Evidence for pelvic osteotomy
A retrospective study compared 22 DPO-treated dogs with four untreated candidates. Radiographic scores were better in the treated group at later follow-up, but the small untreated group limits certainty. A separate series described improvement in eight carefully selected dogs aged 10–28 months. That supports considering some older dogs; it is not evidence that all adult arthritic hips can benefit.
ACVS owner guide · Jenkins and colleagues, 2020 · Petazzoni and Tamburro, 2022
Aftercare and outcome
The recovery plan depends on the operation
Hip operations do different jobs, so their recovery plans differ too. Follow the instructions given for your dog's operation, medicines and rechecks.
Removing the ball and neck (FHO/FHNE)
Rebuild movement with soft tissue support; there is no replacement joint to protect in the same way as THR.
After FHO, controlled early use of the leg and a rehabilitation plan help your dog rebuild movement and muscle. This is different from unrestricted running or jumping.
FHO aims to improve comfort and use of the leg, but your dog may still walk differently. Body size, muscle condition and problems in the other legs can affect the result. If your dog stays painful or uses the leg poorly, arrange a recheck.
Total hip replacement (THR)
Protect the new ball and socket while the surrounding tissues recover.
The new joint needs protection while the tissues heal. This means controlled leash walks, a small rest area and follow-up checks before increasing activity. Feeling better does not mean the hip is ready for running or jumping.
Recovery after puppy or pelvic surgery
Early growth surgery (JPS)
Follow growth after JPS: the socket’s change develops as your puppy grows.
After JPS, care mainly involves looking after the surgical wound and limiting activity for a short period. Your puppy still needs checks as they grow. The operation does not guarantee normal hips or prevent all arthritis.
Rotating the socket (DPO/TPO)
Protect the healing pelvis: the plate holds the changed position while bone joins.
The pelvis has been cut and held in its new position with a plate. Activity stays controlled while the bone heals. Follow-up X-rays help decide when activity can increase.
Risks include infection, problems with the plate or screws, nerve injury, slow healing and hip disease that continues or worsens.
What if your dog seems to have grown out of it?
Some dogs look more comfortable as they mature. Healing and scar tissue around the joint can reduce obvious looseness, and symptoms may come and go.
That improvement does not restore a normal ball-and-socket joint. Existing damage may remain, and arthritis can become painful later. At a recheck, the surgeon can assess your dog’s comfort, whether a treatment window has passed, or whether something else is causing the limp.
Follow your dog’s discharge plan for medicines, wound care, exercise and rechecks. If pain or leg use is getting worse, or the wound opens or leaks, contact the surgical team promptly.
Veterinary teams: hip dysplasia referral checklist
Puppies: include age in weeks and flag for early hip assessment.
Send with referral
- Age, breed, weight and BCS with scale.
- Affected side, onset, mobility limits and orthopedic/neurologic findings; gait video if available.
- Current medicines, doses, response/adverse effects; rehabilitation tried; previous hip/pelvic surgery.
- Original pelvic images and reports, if taken.
- Blood results, if available; relevant medical history.
At the hip consultation
- PennHIP X-rays and assessment.
- VD hip-extended assessment: Norberg angle and femoral head coverage (FHC) measurements and OA scoring by Dr. Wood.
- Ortolani/Barlow testing and reduction/subluxation angles under sedation.
Coordinate with the surgical team
- Calibrated planning views ± CT, when needed for the proposed operation.
- Bloodwork for NSAID/anaesthetic planning.
Sources and further reading
This guide draws on the hip chapter in Brinker, Piermattei and Flo's Handbook of Small Animal Orthopedics and Fracture Repair (2016), the studies linked above, and the ACVS hip dysplasia guide.