Locked stifle (Upward fixation of the patella)
A locked stifle is intermittent upward fixation of the patella — a movement problem in which a hind limb sticks in extension, then snaps forward when it unlocks — not general lameness and not kissing spine. A photograph cannot diagnose a locked stifle. A still cannot tell a locked stifle from stringhalt, shivers, ordinary hind-limb stiffness, or a hitch. Diagnosis is a vet exam, often watching the horse walk and trot. The gait scan is a first look at the hind-limb stride to share with a vet, not a locked-stifle test, and there is no locked-stifle scanner.
Symptoms to watch for
A hind limb that sticks in extension, then snaps forward when it unlocks — the lock-and-release is the clue, not a still photo
A toe that drags while that hind limb is stuck straight, then a sudden catch-up stride
An intermittent hitch: the horse may look even between episodes, then lock again when it starts, walks, or turns
Reluctance to go forward, step under, or flex that stifle after standing or at the start of work
A hind-limb hitch that can look like stringhalt, shivers, ordinary stiffness, or a catch — a still cannot tell them apart
Some horses look normal at rest; the first sign is a lock-and-release at walk — a reason to book a vet, not a photo verdict
Common causes
- Intermittent upward fixation of the patella — the medial patellar ligament can catch so the hind limb stays locked in extension until it releases
- A straight-stifled build, weak quadriceps, or a young or out-of-work horse — conformation and condition are clues, not a diagnosis
- Not stringhalt (exaggerated hind-limb flexion), not shivers (trembling, often worse when backing), and not ordinary hind-limb stiffness — a still cannot tell a locked stifle from those
- Not kissing spine and not a generic lame gait — those are different problems and need a vet
Prevention
- Keep the horse in regular, gradual work so the stifles stay muscled — long rest then sudden work is extra load
- Warm up before hard work and build collected or hill work gradually
- Watch for a hind limb that sticks then snaps, a dragging toe, or a new hitch at walk and rest rather than riding through it
- Do not treat a photo, a lock-and-release, or a scan result as a diagnosis
- A gait clip can help you and the vet look at the hind-limb stride — it does not confirm or rule out a locked stifle, and it cannot tell a locked stifle from stringhalt, shivers, ordinary stiffness, or a hitch
What to do
- 1
Book a vet visit if a hind limb sticks in extension and then snaps forward, if the toe drags, or if you see a new hitch at walk. Diagnosis is a vet exam, often watching the horse walk and trot — not a photograph.
- 2
Stop riding through a lock. Rest the horse and do not push collection or hills hoping the catch will work out.
- 3
If you record a gait clip, film a few strides at walk and trot on a hard, level surface from the side — that is a video, not a still, and it is a first look to share, not a diagnosis.
- 4
Use a gait scan only as a first look at the hind-limb stride to share, not as a locked-stifle test. There is no locked-stifle scanner.
- 5
If upward fixation of the patella is confirmed, follow the plan your vet prescribes — that may include conditioning, controlled exercise, or further exam. Do not start a treatment protocol from a photo.
- 6
Keep the vet on the same page. Share what you see; do not treat a photo as a verdict.
Pick up the phone if…
Schedule a vet visit if a hind limb sticks in extension and then snaps forward, if the toe drags, if you see a new hitch at walk or after standing, or if the catch is happening more often. Call sooner if the horse will not bear weight, cannot unlock the limb, or is in obvious pain. A photograph cannot diagnose a locked stifle. A still cannot tell a locked stifle from stringhalt, shivers, ordinary hind-limb stiffness, or a hitch. Diagnosis is a vet exam, often watching the horse walk and trot. The gait scan is a first look at the hind-limb stride, not a locked-stifle test, and there is no locked-stifle scanner.
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Educational content only. Not a substitute for veterinary advice.