Knee Flashcards
Classification: Modified hinge joint
Degrees of freedom: Flexion, extension, internal rotation, external rotation
Function: Weight-bearing joint, susceptible to degenerative changes
Tibiofemoral Joint:
Angle between ASIS-patella line and patella-tibial tuberosity line
Normal range: Males: 13 degrees, Females: 18 degrees
Altered Q-angle: Affects patellar position, leading to genu varum or genu valgum
Q-Angle:
Abnormal angulation observed during sitting
Characteristics: Anteverted hip, laterally dislocated patella, externally rotated tibia
Bayonet’s Sign
Angle between femur and tibia axes
Normal range: 180-185 degrees
Altered angle: Indicates genu varum (decreased) or genu valgum (increased)
Medial Tibiofemoral Angle/Knee Angle
Genu Valgum vs. Genu Varum
Genu valgum: Knees close together, tibia outward
Genu varum: Knees apart, tibia inward
Features: Largest sesamoid bone, contains five facets
Function: Incongruent joint, contact during extension only at inferior pole
Patellofemoral Joint:
Softening of cartilage underneath the patella
Cause of knee pain, especially over full flexion
Most affected area: Odd facet
Cinema Sign: Knee pain upon standing after prolonged sitting
Chondromalacia Patellae
Umbrella term for anterior knee pain
Associated with patellar malalignment and tracking issues
Symptoms: Pain during stairs, prolonged sitting (movie sign), squatting, etc.
Patellofemoral Pain Syndrome (PFPS):
Procedure: Patient supine with knee flexed at 30 degrees, examiner laterally deviates patella
Positive test: Quads contraction or apprehension, indicating possible patellar subluxation or dislocation
Special Test: Fairbank’s Apprehension Test:
Inflammation of synovial fold causing snapping or catching sensation
Plica syndrome
Inflammation or impingement of infrapatellar fat pad causing anterior knee pain
Fat pad syndrome
Inflammation of patellar or quadriceps tendon, common in jumping sports
Tendonitis/jumper’s knee:
Irritation of IT band against lateral femoral condyle, seen in runners or cyclists
IT band friction syndrome:
Inflammation of bursa between skin and patella, causing swelling and tenderness
Inflammation of bursa between skin and patella, causing swelling and tenderness
Bone tissue death leading to retropatellar pain, most common in medial knee
Osteochondritis dissecans
Where is the pain felt in these cnditions
Sinding-Larsen Johansson syndrome:
Osgood-Schlatter disease:
Sinding-Larsen Johansson syndrome: Pain over inferior pole of patella
Osgood-Schlatter disease: Pain over tibial tuberosity
Special Tests for PFPS:
Clarke’s Sign: Tests for patellar maltracking; patient in supine, examiner applies pressure on superior patella while patient contracts quadriceps.
Eccentric Step Test: Assesses patellar tracking during eccentric loading of quadriceps; patient descends a step with control.
Noble Compression Test: Evaluates for IT band friction syndrome; patient in supine with knee flexed, examiner applies pressure over lateral femoral condyle.
Encloses patellofemoral and tibiofemoral joints; reinforced by structures like subcrureus.
Two layers: Synovial (inner), Fibrous (outer); patellar plica are remnants of synovial membrane and can cause pain if not reabsorbed.
Joint Capsule
Most commonly affected in plica syndrome is infrapatellar; medial plica is most symptomatic.
Patellar Plica:
housemaid’s knee (),
vicar’s knee (),
clergy’s knee (),
Baker’s cyst ().
housemaid’s knee (prepatellar),
vicar’s knee (infrapatellar),
clergy’s knee (infrapatellar), and
Baker’s cyst (popliteal).
Fibrocartilaginous discs shaped like “MCLO”; functions include enhancing joint congruency, distributing weight-bearing forces, reducing friction, and absorbing shock.
More mobile: Lateral meniscus; Susceptible to injury: Medial meniscus.
Menisci
Meniscal Attachments:
Transverse ligament, patellomeniscal ligaments, coronary ligaments, meniscofemoral ligament, Ligament of Humphry (Anterior PCL), Ligament of Wrisberg.
Triad of the Knee:
Consists of PCL, MCL, and ACL.
Nutrition: Only outer portion has blood supply; inner portion receives nutrition via diffusion.
Innervation: Central position is avascular.
Meniscal Characteristics:
Signs and Symptoms of Meniscal Injury:
Joint line pain, loss of flexion (>10 degrees) and extension (>5 degrees), swelling, crepitus, positive special tests for meniscal integrity.
Effect of Tibial Rotation on Cruciate and Collateral Ligaments:
Lateral rotation of tibia (ERCOLTA): Medial and lateral collateral ligaments become taut, while medial and lateral cruciate ligaments become lax.
Medial rotation of tibia (IRCRUTA): Cruciate ligaments become taut, while collateral ligaments become lax.
Primary rotatory stabilizers of the knee, restraining antero-posterior tibial motion and internal rotation of the tibia.
Intracapsular and extrasynovial (ICES); no intrinsic source of depression, necessitating replacement if damaged.
Cruciate Ligaments:
Special Test for ACL Injury:
Anterior Drawer Test: Knee flexed to 90 degrees.
Lachman Test: Knee flexed to 25 degrees (20-30 degrees); considered better than Anterior Drawer Test due to hamstring contraction.
MOI Tibia anteriorly displaced, externally rotated, with a valgus force.
Anteromedial Instability:
MOI Tibia anteriorly displaced, internally rotated, with a varus force.
Anterolateral Instability:
MOI Tibia posteriorly displaced, internally rotated, with a valgus force.
Posteromedial Instability:
MOI Tibia posteriorly displaced, externally rotated, with a varus force.
Posterolateral Instability:
Screw Home Mechanism/Locking of the Knee
Open Kinetic Chain (OKC): External rotation of the tibia in the last degrees of knee extension.
Closed Kinetic Chain (CKC): Femur internally rotates on the fixed tibia.
Mechanism of Injury: Vulnerable as it passes the fibula, injuries over the fibula can lead to foot drop or steppage gait due to loss of dorsiflexion.
Common Peroneal Nerve:
Mechanism of Injury and Manifestation: Injury directed over the vastus medialis or adductor longus can lead to medial knee pain and loss of sensation in the medial aspect, known as Turner’s sign.
Saphenous Nerve:
