The Knee Joint Flashcards
What are examples of acute injuries, chronic & acute swelling of the knee?
-Acute injuries= fracture, sports/fall, tear, sprain of ligament/soft tissue/cartilage
-Acute swelling= acute gout/flare, RA, septic joint
Chronic swelling= OA, bursitis
Describe the knee joint
- Synovial
- Hinge joint
- 3 bones (distal femur, proximal tibia, patella)
What articulations are formed at the knee?
- 2 femorotibial (medial & lateral)
- Femoropatellar
What movements are possible at the knee joint?
- Flexion (loose some flexion when hip extended due to loss of tension on hamstring)
- Extension
- Medial & lateral rotation (only when the knee is flexed & collateral ligaments relaxed)
What is ‘locking’ of the knee?
As joint approaches full extension femur medially rotates slightly on the tibia, very stable position so thigh muscles can relax
How is the knee unlocked?
Popliteus muscle laterally rotates femur
When is the knee joint weakest?
-Flexion
-Joint is incongruent
Tibial plateau is flat-poor fit to rounded femoral condyles
What are menisci?
- 2 ‘C’ shaped wedges of fibrocartilage
- Thicker at external margins
- External edges attach to fibrous capsule of joint
- Deepen surface for femur to sit it
- Medial meniscus firmly attached to tibial collateral ligament
What are the functions of the menisci?
- Increase joint congruency
- Distribute weight evenly
- Shock absorption
- Assist in locking mechanism
How can meniscal tears occur?
- Due to sports injury or degenerative changes
- Displaced cartilage can become trapped during movement-painful locking
- Treat by repair or resection
- Damage associated with development of osteoarthritis
Name the intra-articular and extra-articular ligaments of the knee
Intra-articular= anterior & posterior cruciate ligaments Extra-articular= fibular & tibial collateral ligaments
Describe the cruciate ligaments
- Inside the knee joint
- Cross obliquely
- ACL is weaker than PCL
What are the attachments of the anterior cruciate ligament?
- Anterior intercondylar region of tibia
- Travels supero-posteriorly to attach to lateral femoral condyle
What are the attachments of the posterior cruciate ligaments?
- Posterior intercondylar region of the tibia
- Travels supero-anteriorly to insert onto the medial femoral condyle
What are the functions of the posterior cruciate ligament?
- Prevents posterior displacement of tibia
- Prevents hyperflexion
- Main stabiliser of the flexed knee when weight bearing
- Can be damaged when landing on tibial tuberosity with flexed knee
What are the functions of the anterior cruciate ligament?
- Prevents anterior displacement of the tibia on the femur
- Prevents hyperextension
- ACL injury occurs when knee is hyperextended or force applied anteriorly
Describe the Tibial collateral ligament
- Flat band attached to medial meniscus and medial margin of tibia
- Prevents abduction of the leg at the knee & rotation during extension of the knee
Describe the location and action of fibular collateral ligament
- Cord like band
- Prevents adduction of the leg at the knee & rotation during extension of the knee
- Lateral femoral epicondyle to inferior fibular head
What is an unhappy triad injury?
- Caused by excessive lateral twisting of flexed knee or blow to lateral side of extended knee
- Abduction tears tibial collateral ligament & medial meniscus
- Rotation ruptures ACL
What muscles act on the knee joint?
- Quadriceps
- Hamstring (post. thigh)
- Gracilis
- Sartorius
- Iliotibial tract
- Main stabilisers of the knee
How can the patella be dislocated?
- More common in females
- Rectus femoris, Vastus intermedius, Vastus lateralis all pulling superolaterally
- Counteracted by more horizontal pull of vastus medialis
What abnormal alignments of the knee can occur?
- Genu varum= bow leg (tibia adducted wrt femur)
- Genu valgum= knock knee (tibia abducted wrt femur)
What muscles are responsible for medial & lateral rotation of the knee?
- M=Gracilis, sartorius, popliteus, semitendinosus/membranosus
- L= Biceps femoris
