Upward Fixation of the Patella
Learn what the condition is, how it may be detected early, how it is treated or managed, and which breeds or species are linked to it.
Condition snapshot
A concise guide to the condition’s pattern, detection, management and urgency.
This snapshot is a general guide, not a diagnosis or treatment plan. New, severe or worsening signs require veterinary assessment.
About the condition
Upward fixation of the patella occurs when the medial patellar ligament remains hooked over the medial trochlear ridge of the femur instead of releasing as the horse moves. This locks the reciprocal apparatus with the hindlimb extended. The horse may drag the toe behind with the fetlock flexed, then release the leg with a sudden snap. A milder delayed release causes a brief jerky step when moving off or during downward transitions.
Young, poorly muscled horses and ponies are most often affected, particularly with straight hindlimb conformation, rapid loss of condition or a period out of work. Older horses can develop signs after stifle trauma or discipline change. Repeated locking can cause stifle soreness, reluctance on hills or deep footing and secondary cartilage damage.
The condition is mechanical, not true paralysis. It can be confused with stringhalt, shivers, fibrotic myopathy or a horse simply resisting movement. In a complete lock the limb cannot flex normally, which can alarm owners and tempt forceful pulling. Some episodes release spontaneously, but a persistently fixed limb needs safe veterinary assistance.
Most intermittent cases improve with maturity, strength and conditioning. Stall rest generally worsens the underlying poor muscle tone and is contraindicated unless required after a procedure or for another injury. Prognosis is good when the characteristic movement is recognised early and concurrent stifle disease is absent. Chronic painful cases require imaging before assuming that muscle weakness is the only problem.
The medial patellar ligament can remain hooked over the medial trochlear ridge, locking the stifle in extension and leaving the limb trailing with the toe dragging. Mild delayed release causes a jerky step rather than fixed locking. Young, poorly muscled or straight-limbed horses are predisposed, and the problem differs from painful stifle arthritis.
Screening & Early Detection
Diagnosis is usually made by observing the typical extended locked limb or delayed patellar release. The horse is watched starting from rest, backing, turning and making transitions on safe footing. The patella can sometimes be fixed or released manually by an experienced veterinarian, but repeated provocation is unnecessary when video clearly documents the event.
Stifle palpation evaluates patellar ligaments, effusion, pain and muscle symmetry. Radiographs are indicated when lameness, femoropatellar swelling, trauma or persistent signs suggest osteochondrosis, arthritis or patellar injury. Ultrasound can examine the ligaments and accessible soft tissues. A full lameness examination excludes other sources of a jerky hindlimb gait.
Owners should record frequency, duration, relation to rest and ability to self-release. A limb that remains fixed, a horse at risk of falling or new marked pain warrants prompt help. Stringhalt produces hyperflexion during forward walking, whereas upward fixation holds the limb extended; distinguishing the motion prevents inappropriate treatment.
Video from the first steps after rest often captures an intermittent catch missed later in the examination.
Treatment & Management
A veterinarian can release a fixed patella by controlled backward movement with directed patellar pressure or by carefully bringing the limb forward. This is performed with attention to handler safety and any concurrent injury. Repeated home force should not be used on a painful or unstable horse.
For intermittent uncomplicated cases, daily progressive exercise builds quadriceps and stifle strength. Hill work, poles and transitions are introduced according to age and soundness. Turnout is maximised and prolonged stall rest avoided. Adequate calories and protein support muscle gain without creating obesity. Balanced trimming and a facilitated breakover can help selected horses.
Persistent cases may receive medial patellar ligament desmoplasty, in which small incisions stimulate thickening and alter release. Rehabilitation after the procedure differs from conservative conditioning and follows the surgeon’s restrictions. Complete medial patellar ligament desmotomy was used historically but is now largely avoided because patellar fragmentation and instability can follow. Concurrent OCD or arthritis receives its own treatment. Many young horses improve without surgery, while recurrent painful locking that resists conditioning has a good prognosis after appropriately selected desmoplasty.
Farriery may improve breakover, but exaggerated toe extensions can create harmful leverage and are avoided.
Breeds or species affected
Akhal-Teke
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Anglo-Arabian
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Arabian
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Barb
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Caspian
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Kathiawari
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Marwari
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Shagya Arabian
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Thoroughbred
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American Quarter Horse
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American Paint Horse
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Appaloosa
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Australian Stock Horse
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Brumby
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Waler
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Morgan
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Standardbred
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American Saddlebred
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Tennessee Walking Horse
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Missouri Fox Trotter
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Rocky Mountain Horse
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Peruvian Paso
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Criollo
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Mustang
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Canadian Horse
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Andalusian
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Lusitano
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Lipizzaner
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Friesian
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Dutch Warmblood
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Hanoverian
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Holsteiner
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Oldenburg
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Westphalian
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Trakehner
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Selle Français
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Belgian Warmblood
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Danish Warmblood
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Swedish Warmblood
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Swiss Warmblood
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Australian Warmblood
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Irish Sport Horse
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Cleveland Bay
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Württemberger
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Zangersheide
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Knabstrupper
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Orlov Trotter
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Camargue
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Icelandic Horse
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Pony of the Americas
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Quarter Pony
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Miniature Horse
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Clydesdale
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Shire
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Percheron
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Belgian Draft
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Suffolk Punch
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American Cream Draft
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Ardennes
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Breton
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Boulonnais
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Comtois
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Dutch Draft
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North Swedish Horse
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Norwegian Fjord
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Haflinger
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Gypsy Cob
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Irish Draught
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Welsh Pony and Cob
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Connemara Pony
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New Forest Pony
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Dartmoor Pony
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Exmoor Pony
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Shetland Pony
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Highland Pony
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Fell Pony
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Dales Pony
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Australian Pony
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Finnhorse
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Black Forest Horse
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