Recurrent Dislocation of Patella | Chondromalacia of Patella Flashcards
(10 cards)
Attachments of Patella
Patella is a sesamoid bone, wrapped inside the Quadriceps Femoris tendon. Patella along with the tendons attaches to the Tibial Tubercle on the anterior surface of Tibia.
Patella sits over the Trochlear grove, and slides over the condyles of femur on it’s anterior surfaces.
Functionally Patella acts as a levarage for extension strength of the leg/knee
Patella is also surrounded by other tendons, namely Patellofemoral ligaments medial and lateral. Dislocations of Patella are usually due to weak/damaged Medial Patellofemoral ligament
Predisposing factors for Recurrent Patellar dislocations
- Ligament or joint hypermobility [Ehler Danlos, Marfan syndrome]
- Small Patella
- Weak Vastus medialis muscle
- High Patella position
- Deformity of knee
- Family history
- Patellar subluxation
- Increase in Q angle [angle between longitudinal of leg vs line between Ant. sup. Iliac spine to middle of patella]
- Weak Medial Patellofemoral ligament [from injury]
Over 90% patellar dislocations results from a twisting injury when the knee is simultaneously in flexion and under valgus strain
Clinical features of Recurrent dislocations
- Unexpectedly occurs when quadriceps is contracted with knee in flexion
- Often bilateral
- Severe acute pain, cannot straighten knee
- Ristricted ROM and instability of knee
- Dislocation also occurs in extension of knee
- Posterolateral dislocation of patella
- Xray shows laterally displaced and rotated patella. It also rules out osteochondral fractures. May reveal predisposing factors of patellar dislocation anatomy
Predisposition to Osteoarthritis
Physical Exam signs
Positive Lateral Patellar Apprehension test: Knee flexed at 30 degree, quads relaxed. Lateral pressure applied to medial side of patella, which displaces patella laterally triggering apprehension and discomfort in patient
Patella can be manually reduced but patient complains it has happened multiple times
Swollen knee may be present if its the first ever dislocation, fluid aspiration may be needed to rule out osteoarthritis or septic arthritis
Congenital Patellar dislocation - Lateral displacement that cannot be manually reduced and often presenting at birth but missed on physcial exam
Treatment of Recurrent dislocation
Conservative management:
- Manual reduction, guiding patella medially onto the trochlear groove while extending knee
- Pain management
- Immobilization and weight-baring as tolerated for upto 6 weeks
- Physical therapy to strenghen tendons and quads
- Indicated for first dislocation with no osteochondral fractures or significant soft tissue loss or patients not willing to get surgery
Surgical Management:
- Arthroscopy [to repair intraarticular loose bodies or osteochondral fractures]
- Repair/Reconstruction of Medial Patellofemoral ligament
- Osteotomy [to improve bony aligment of patella on groove] aka Tibial Tubercle Transfer
- Trochleoplasty [for trochlear dysplasia, alters shape to better fit patella]
- Indicated for recurrent dislocations, Osteochondral fracture evidence, significant injury to stabilizing ligaments, failure of conservative management
Chondromalacia Patellae definition
It is also known as the “Runner’s Knee” as long distance runners tend to have this problem.
It is a condition of softening of the underside cartilage of Patella causing diffuse pain and in and around the knee
Chondromalacia classification
Outerbridge MRI classification of Chondromalacia:
- Grade 0: Normal Cartilage
- Grade I: Surface intact and heterogenous, high signal intensity
- Grade II: Fissures and fragmentation extending down to the articular surface
- Grade III: Partial thickness defect, with focal ulceration
- Grade IV: Exposed subchondral bone
Chondromalacia Presentation
- Diffuse pain in perpatellar or retropatellar knee area
- Onset is vague and insidious
- Pain increases with climbing stairs/squatting/running/Prolonged sitting with bent knee/Kneeling
- Quad muscle atrophy
- Patella maltracking
- Palpable crepitus
- Pain with patella compression with knee ROM or Resisted knee extension
Chondromalacia Imaging
MRI: best modality to view articular cartilage. Abnormal cartilage high signal in T2
Radiographs: anatomic disturbances in patella causing chondromalacia
CT: Ligament alignments and fracture detection
Chondromalacia Treatment
Conservative:
- Rest
- Rehabilitation/Physiotherapy [Vastus medialis and core strengthening, hip external rotator strengthening]
- NSAIDS for pain
- Done for minimum 1 year
- Activity modification
Surgical:
- Arthroscopic debridment [MRI grade II-III | Mechanical or Radiofrequency methods]
- Lateral Retinacular release
- Patellar Realignment Surgery [Anterior tubercle elevation, Osteotomy, Medial Patellofemoral ligament reconstruction]
