ISSN 2398-2977      

Patella: luxation

pequis

Introduction

  • Cause: uncommon congenital or rare acquired (secondary to joint disease Musculoskeletal: osteoarthritis (joint disease) or trauma to stifle) disorder.
  • Signs: hindlimb lameness, may be uni- or bilateral, stifle swelling, abnormal gait.
  • Diagnosis: manual examination, radiography.
  • Treatment: surgery.
  • Prognosis: poor to guarded for athletic career.

Pathogenesis

Etiology

  • Luxation of the patella is usually lateral due to the larger medial trochlear ridge of the distal femur. Medial displacement is normally only seen following trauma to the region.
  • Congenital malformation and hypoplasia of the femoral trochlea, particularly the lateral ridge, is commonly associated with lateral luxation, although the condition can occur in foals with apparently normal conformation.
    • In some breeds it is an inherited condition caused by a monogenic autosomal recessive gene.
    • Usually presents in the young foal.
  • In the adult horse, luxation of the patella is much less common and usually related to a traumatic incident. In traumatic cases, luxation can be medial, lateral or even distal.
  • Rarely, severe osteochondrosis Bone: osteochondrosis lesions of the lateral trochlear ridge can lead to loss of the bone structure and secondary lateral luxation. This has been seen in older foals and yearlings, often with very straight hindlimb conformation.

Predisposing factors

General

  • Breed.
  • Previous stifle injury/disease.

Specific

  • Abnormal conformation of the femoropatellar joint.

Pathophysiology

  • Congenital abnormality in the topography of the femoropatellar joint, eg shallow trochlea groove / hypoplastic trochlear ridges → quadriceps flexion pulls patella laterally.
  • Femoropatellar joint disease: osteoarthritis Musculoskeletal: osteoarthritis (joint disease), osteochondrosis Bone: osteochondrosis → remodeling of the trochlea ridges → loss of normal tracking for patella → luxation.
  • Trauma to patella ligaments → patella instability → luxation.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Hall M S, Jalim S L & Russell T M (2010) Distal luxation of the patella in a horse. Aust Vet J 88 (10), 396-398 PubMed.
  • O'Meara B & Lischer C J (2009) Surgical management of a pony with a traumatic medial luxation of the patella. Equine Vet Educ 21 (9), 458-463 VetMedResource.
  • Busschers E (2009) Patellar luxation in horses: Treatment and prognosis. Equine Vet Educ 21 (9), 464-466 Wiley Online Library.
  • Milner P (2009) Lateral patellar luxation associated with severe osteochondritis dissecans (OCD) of the lateral trochlear ridge. UK Vet 14 (7), 5-6 VetMedResource.
  • Hart J C A, Jann H W & Moorman V J (2009) Surgical correction of a medial patellar luxation in a foal using a modified recession trochleoplasty technique. Equine Vet Educ 21 (6), 307-311 VetMedResource.
  • Talbot A M & Singer E R (2009) Luxation of the patella in foals. Equine Vet Educ 21 (6), 313-314 VetMedResource.
  • Englebert T A et al (1998) Lateral patellar luxation in miniature horses. Vet Surg 22 (4)293-297 PubMed.
  • Kobluk C N (1998) Correction of patellar luxation by recession sulcoplasty in three foals. Vet Surg 22 (4)298-300 PubMed.
  • Hermans W A, Kersjes A W, van der Mey G J & Dik K J (1987) Investigation into the heredity of congenital lateral patellar (sub)luxation in the Shetland pony. Vet Q (1), 1-8 PubMed.

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