Patellar Luxation Flashcards
patella
largest sesamoid bone
part of the EXTENSOR apparatus
insertion of the quadriceps tendon via the patellar tendon
what are the muscles of the quadriceps and where do they originate
vastus lateralis (prox. femur)
vastus medialis (prox. femur)
vastus intermedius (prox. femur)
rectus femoris (ilium)
patellar luxation
partial or intermittent displacement of the patella from its normal position in the cranial trochlear sulcus (patellar groove)
most common to luxate MEDIALLY
bilateral is common
medial patellar luxation
malalignment of the quadriceps mechanism medial to the joint
clinical signs of medial patellar luxation
decreased growth medially, normal growth laterally leading to “cowboy bowleg” appearance (genu varus)
tibia rotates internally
lateral patellar luxation
malalignment of the quadriceps mechanism lateral to the joint
clinical signs of lateral patellar luxation
normal growth medially, decreased growth laterally leading to “knock knees” appearance (genu valgum)
tibia rotates externally
grade 1 luxation
no clinical signs
patella stays in position but can be manually pushed out
grade 2 luxation
patella occasionally luxates causing intermittent lameness (“skipping steps”)
grade 3 luxation
patella is always luxated causing continous lameness but can be manually pushed back in
grade 4 luxation
patella is always luxated causing continuous lameness but can NOT be manually pushed back in
clinical signs of patellar luxation
intermittent to continuous lameness
abnormal stifle joint function
genu varum or valgus
secondary angular limb deformities
diagnosis of patellar luxation
- signalment
- PE
- orthopedic exam
- radiographs
- CT
PE/orthopedic exam considerations
try manually luxating the patella medially and laterally
medial: place leg in extension and internally rotate foot, then push patella medially
lateral: place leg in flexion and externally rotate foot, then push patella laterally
luxating patella on radiographs
displacement of patella relative to patellar groove
assess valgus/varum
look for OA in stifles/hips
when should you CT luxating patellas
surgical planning for more advanced corrections
luxating patella treatment
grade 1: none bc no clinical signs
grade 2: depends on age and frequency of luxation
grade 3: surgery
NOTE: if concurrent CCL tear then must repair
4 in 1 surgical technique
- ST release
- ST imbrication
- recession trochleoplasty
- tibial tuberosity transposition
ST release
loosening of the tight fascia on the side of the luxation
ST imbrication
tightening of the loose fascia on the opposite side as the luxation
recession trochleoplasty
deepening of the patellar groove to keep patella in place by removing articular cartilage, shaving down subchondral bone, then replacing the cartilage
tibial tuberosity transposition (TTT)
realigning the quadriceps by cutting the tibial tuberosity and sliding sideways in the opposite direction as the luxation
