Is your horse dragging a hind toe, fighting the canter, or struggling on hills? Those small changes are easy to blame on attitude, but they can point to a stifle problem. A stifle joint injury in a horse is one of the more common sources of hind limb lameness, and it shows up in everything from backyard trail horses to racehorses.
Here's what horse owners and veterinarians should know about stifle injuries: what they look like, why they happen, how they're diagnosed, and the treatment options your veterinarian may recommend.
The stifle is the joint in a horse's hind leg where the femur meets the tibia, roughly matching the human knee. It sits high on the leg, just in front of the flank.
The stifle joint is the largest joint in the horse's body, made up of three joints (the femoropatellar joint and the medial and lateral femorotibial joints) supported by two menisci and 14 ligaments.
Horses have three patellar ligaments, while humans have one. Because the stifle carries so much load during pushing off, stopping, and turning, small injuries can show up as big changes in how a horse moves.
The most common signs of a stifle injury are hind limb lameness, a shortened stride, and resistance to work that loads the hindquarters. Signs are often subtle at first and may improve once a horse warms up.
Watch for:
In 2025, the Merck Veterinary Manual noted that meniscal injuries can range from mild, chronic lameness to sudden, severe lameness, and that joint swelling is a common finding. If you notice any of these signs, call your veterinarian before continuing work.
The most common stifle injuries in horses are meniscal tears, upward fixation of the patella (locking stifle), ligament injuries, subchondral bone cysts, and osteochondrosis. Each one affects a different part of the joint.
Common Stifle Injuries in Horses |
||
|---|---|---|
|
Injury |
What Happens |
Most Often Seen In |
|
Meniscal tear |
Damage to the cartilage pads that cushion the femur and tibia; the medial meniscus is affected most often |
Adult performance horses |
|
Upward fixation of the patella (locking stifle) |
A patellar ligament catches on the femur and locks the leg straight |
Young horses and ponies with weak hind end muscles |
|
Collateral or patellar ligament injury |
Strain or tearing of the ligaments that stabilize the joint |
Horses with trauma or hard stops and turns |
|
Subchondral bone cyst |
A fluid-filled defect in the bone under the joint cartilage |
Young horses |
|
Osteochondrosis (OCD) |
Abnormal cartilage development that can leave flaps or fragments |
Young, growing horses |
|
Osteoarthritis |
Gradual joint wear, often after earlier cartilage damage |
Older horses or those with past injury |
A locking stifle, or intermittent upward fixation of the patella, happens when the medial patellar ligament catches on the femur and locks the hind leg straight.
According to the Merck Veterinary Manual's 2025 review, it most often affects young horses and ponies in poor body condition with weak musculature, and straight hind limb conformation may play a role.
Meniscal tears usually come from loading and twisting forces on the joint, like sudden stops, sharp turns, or a bad step. Because the menisci sit deep in the joint, these injuries can be hard to see without advanced imaging or arthroscopy.
Most stifle joint injuries come from a mix of workload, conformation, and conditioning. Fast stops, sharp turns, and repeated hard pushes off the hind end put the most stress on the joint.
Barrel racing, cutting, eventing, harness racing, and upper-level dressage are among the higher-risk disciplines. Conformation matters too. Straight hind legs and low heels with long toes can increase strain on the stifle.
What about horses that aren't in hard work? Weak hindquarter muscles are a common factor in locking stifle, which is why horses coming back from time off or young horses still building strength can run into trouble.
Our Take: We see a lot of prescriptions for performance horses, but stifle problems aren't just a competition issue. A pasture horse that's been off for months can be just as vulnerable when it goes back to work. A gradual return plan, built with your veterinarian, is worth the extra weeks.
Veterinarians diagnose stifle injuries with a lameness exam, flexion tests, and nerve or joint blocks, then confirm with imaging. Blocking the stifle joints helps pinpoint whether pain is coming from the stifle or somewhere else in the leg.
Treatment for a stifle joint injury depends on the type of injury, and most plans start with rest and anti-inflammatory medication followed by controlled rehabilitation. Your veterinarian may also recommend joint injections, corrective shoeing, or surgery.
Stifle Injury Treatment Options |
||
|---|---|---|
|
Treatment |
What It Involves |
Prescription Needed? |
|
Rest and controlled rehab |
Stall or small paddock rest, then a gradual return to work |
No, but follow your veterinarian's plan |
|
NSAIDs |
Anti-inflammatories such as phenylbutazone or firocoxib |
Yes |
|
Joint injections |
Corticosteroids or hyaluronic acid injected into the joint by a veterinarian |
Yes |
|
Conditioning program |
Hill work, lunging and strengthening exercises, often used for locking stifle |
No |
|
Corrective shoeing |
Farrier adjustments to support hind limb mechanics |
No |
|
Surgery |
Arthroscopy for meniscal or cartilage damage, or ligament splitting for locking stifle |
Performed by a veterinary surgeon |
NSAIDs like phenylbutazone and firocoxib are commonly prescribed to manage pain and inflammation during rest.
For more on these options, see our guide to equine pain management →
For locking stifle, the Merck Veterinary Manual describes conditioning to build the quadriceps as the first step, with turnout encouraged and stall rest discouraged. Horses that don't respond may need ligament injections or a procedure that splits the medial patellar ligament.
Some owners also add joint supplements such as MSM, hyaluronic acid or omega-3s. Talk with your veterinarian before starting one, since supplements support care but don't replace treatment.
Veterinarians, send equine prescriptions to Mixlab →
Along with stifle injuries, the most common horse injuries involve tendons and ligaments, hooves, and bones. Many show up as lameness, so a veterinary exam is the fastest way to know what you're dealing with.
Common Horse Injuries at a Glance |
||
|---|---|---|
|
Injury Type |
Examples |
Common Signs |
|
Tendon and ligament |
Bowed tendon, suspensory desmitis |
Heat, swelling, lameness |
|
Hoof |
Abscess, bruise, laminitis |
Heat in the hoof, strong digital pulse, reluctance to move |
|
Joint |
Stifle injury, osteoarthritis |
Swelling, stiffness, shortened stride |
|
Bone |
Stress fracture, splint |
Sudden or worsening lameness, localized pain |
|
Muscle |
Tying-up (exertional rhabdomyolysis) |
Stiffness, sweating, reluctance to move after work |
Horse racing injuries follow the same patterns, but speed and workload make many of them more frequent. Injuries in horse racing and other performance sports often involve tendons, bones, and joints like the stifle. Whatever the injury, quick action and a clear plan from your veterinarian matter most.
Mixlab is an equine pharmacy that fills veterinarian prescriptions for horses, including anti-inflammatories and other medications used for injury care. Your veterinarian sends the prescription, and we prepare and ship it.
Questions about your horse's prescription? Contact our team →
It depends on the injury. The Merck Veterinary Manual describes the outlook for meniscal injuries as guarded to fair, and poorer when tears are severe or arthritis is present. Locking stifle often responds to conditioning, especially in young horses. Your veterinarian can explain what to expect for your horse.
Healing time varies widely by injury type and severity. For example, the Merck Veterinary Manual notes about 2 months of stall or small paddock rest after medial patellar ligament splitting for locking stifle. Meniscal and ligament injuries often need longer, carefully staged rehab set by your veterinarian. Mixlab can fill any medications your veterinarian prescribes during that time.
Not until your veterinarian clears it. Riding a horse with an active stifle injury can make the damage worse. Once your veterinarian approves a return, most plans start with walking and slowly add trot, canter, and hill work as the horse builds strength.
Sticky stifle is a common name for delayed patellar release, a milder form of locking stifle. The patella releases late, so the horse's hind leg may look jerky when moving off or slowing down. It's most common in young horses and ponies with weak hindquarter muscles.
Horses in disciplines with sudden stops, sharp turns, and fast work face a higher risk, including barrel racers, cutting horses, eventers, harness racers, and upper-level dressage horses. Young horses, horses with straight hind legs, and horses returning from time off are also more prone to stifle problems.
Not always. Many stifle problems start with rest, anti-inflammatories, and rehab, and Mixlab fills veterinarian prescriptions for NSAIDs like phenylbutazone and firocoxib. Veterinarians typically recommend arthroscopy when a horse doesn't respond to conservative care or imaging shows meniscal or cartilage damage. Locking stifle that doesn't improve with conditioning may need a ligament splitting procedure.
Resources:
Durgam, Sushmitha S. Meniscus and Meniscal Ligament Injuries in Horses. Merck Veterinary Manual, 2025.
Durgam, Sushmitha S. Intermittent Upward Fixation of the Patella and Delayed Patella Release (Locked Stifle) in Horses. Merck Veterinary Manual, 2025.
Meggitt, Jane. Stifle Lameness in Horses: Causes, Treatment and Prevention. Mad Barn, updated 2026.
Loving, Nancy S. Diagnosing Stifle Disease. TheHorse.com, 2007.