Week 9 - Knee Joint Flashcards
What type of joint is a knee joint?
A hinge type synovial joint
What are the articulating surfaces of the knee joint?
- Tibiofemoral: the medial and lateral condyles of the femur articulate with the tibia
- Patellofemoral: the anterior and distal part of the femur articulates with the patella
What does the tibiofemoral joint do?
The weight bearing joint of the knee
What does the patellofemoral joint do?
Allows the quadriceps femoris to be inserted directly over the knee
Describe the femoral condyles
- The medial condyle is larger than the lateral, so it takes more weight
- Between the condyles:
- – Anteriorly = shallow depression for patella articulation
- – Posteriorly = intercondylar fossa (a deep notch)
- Above the condyles:
- – Femoral epicondyles
Describe the femoral epicondyles
Found above the condyles
- Site of attachment for collateral ligaments
- The medial 1 has the adductor tubercle
Describe the tibial surface
- Tibial plateau
- Medial surface = slightly concave
- Lateral surface = slightly convex
- The 2 surfaces are separated by the intercondylar eminence
- The femoral condyles rest on top of this
What are the menisci in the knee?
Fibrocartilage structures in the knee
- There is a medial and a lateral meniscus
- They are C-shaped
- They attach at both ends to the intercondylar area of the tibia
- The medial meniscus is also fixed to:
- – Tibial collateral ligament
- – Joint capsule
- The lateral meniscus is smaller and does not have any extra attachments
- They are thicker at the edges
What are the functions of the menisci?
- Deepen the articular surfaces of the joint
- Act as shock absorbers
What are the 4 bursa found in the knee joint?
- Suprapatella
- Prepatella
- Semimembranosus
- Infrapatella
Describe the suprapatella bursa
- An extension of the synovial cavity of the knee
- Located between the femur and quadriceps femoris
Where is the prepatella bursa found?
Between the apex of the patella and the skin
Describe the infrapatella bursa
- Split into deep and superficial
- The deep bursa lies between the tibia and the patella ligament
- The superficial lies between the patella ligament and the skin
Where is the semimembranosus bursa found?
- Located posteriorly in the knee joint
- Between the semimembranosus muscle and the medial head of the gastrocnemius
Which ligaments are found in the knee joint?
- Patellar
- Collateral (medial and lateral)
- Cruciate (anterior and posterior)
- Popliteal
What is the patellar ligament?
- A continuation of the quadriceps femoris tendon distal to the patella
- Attaches to the tibial tuberosity
What are the collateral ligaments?
2 strap-like ligaments
- Extracapsular
- Act to stabilise the hinge motion of the knee, preventing any medial or lateral movement
Describe the medial collateral ligament
- Also called the tibial collateral ligament
- A wide and flat ligament, found on the medial side of the joint
- Proximally: attaches to the medial epicondyle of the femur
- Distally: attaches to the medial surface of the tibia
Describe the lateral collateral ligament
- Thinner and rounder than the tibial collateral ligament
- Proximally: attaches to the lateral epicondyle of the femur
- Distally: attaches to a depression on the lateral surface of the fibular head
What are the cruciate ligaments?
- Intracapsular ligaments
- They connect the tibia and femur
- They cross over each other
Describe the anterior cruciate ligament
- Attaches at the anterior intercondylar region of the tibia
- Ascends posteriorly to attach to the femur in the intercondylar fossa
- It prevents anterior dislocation of the tibia onto the femur
- Limits hyperextension
Describe the posterior cruciate ligament
- Attaches at the posterior intercondylar region of the tibia
- Ascends anteriorly to attach to the femur in the intercondylar fossa
- It prevents posterior dislocation of the tibia onto the femur
- The stronger of the 2 cruciate ligaments
- It limits hyperflexion
- In weight-bearing on a flexed knee, it is the main stabiliser
What is the popliteal ligament?
- Oblique
- Arcuate
- Found posteriorly
- They strengthen the capsule
What are the movements of the knee joint and which muscles produce them?
- Extension: quadriceps femoris
- Flexion: hamstrings, gracilis, sartorius, popliteus
- Lateral rotation: biceps femoris
- Medial rotation: semimembranosus, semitendinosus, gracilis, sartorius, popliteus
How can the knee joint be stabilised?
- Deepen the articular surface of the tibial element (menisci)
- Support the joint by outside structures (muscles, ligaments)
How can the collateral ligaments be damaged?
Injury is caused by a force being applied to the side of the knee when the foot is placed on the ground
How can you assess collateral ligament damage
By asking the patient to medially rotate and laterally the leg
- Pain on medial rotation indicates damage to the lateral ligament
- If the medial collateral ligament is damaged, it is more than likely that the medial meniscus is torn, due to their attachment
How can the anterior cruciate ligament be damaged?
- Hyperextension of the knee joint
- By the application of a large force to the back of the knee with the joint partly flexed
What is the effect of anterior cruciate ligament damage?
Can cause a triad of injuries
- Tearing of the ACL causes the unstable femur to shift medially
- This tears the lateral meniscus and the medial collateral ligament
- The medial meniscus can also be torn due to its attachment to the medial collateral ligament
How can the posterior cruciate ligament be damaged?
- ‘Dashboard injury’
- – Occurs when the knee is flexed and a large force is applied to the shins, pushing the tibia posteriorly
- – Often seen in car accidents, where they hit the dashboard
- By hyperextension of the knee joint
- By damage to the upper part of the tibial tuberosity
How can the bursae within the knee joint become inflamed?
- Prepatella: friction between the skin and the patella can cause inflammation
- – Produces a swelling on the anterior side of the knee
- – Known as “housemaid’s knee”
- Infrapatella: friction between the skin and tibia can cause inflammation
- – Results in clergyman’s knee
What is a popliteal cyst?
Also called a Baker’s cyst
- Abnormal fluid filled sacs of synovial membrane in the popliteal fossa
- A sign of chronic knee effusion
What are the hamstrings?
A collective name of the muscles in the posterior compartment of the thigh
- Consists of the biceps femoris, semitendinosus and semimembranosus
- As a group, they act to extend at the hip and flex at the knee
- They are innervated by the sciatic nerve
Describe the biceps femoris
- Has 2 heds: a long and short head
- The most lateral of the muscles in the posterior thigh
- The common tendon of the 2 heads can be felt laterally at the posterior knee
Where is the biceps femoris found?
- Long head origin: ischial tuberosity of the pelvis
- Short head origin: linea aspera on posterior surface of the femur
- The heads form a tendon together, which inserts into the head of the fibula
What are the actions of the biceps femoris?
- Flexion at the knee
- Extension of the leg at the hip
- Laterally rotates at the hip and knee
What is the innervation of the biceps femoris?
- Long head: tibial nerve
- Short head: common fibular nerve
Describe the semitendinosus
- A largely tendinous muscle
- Lies medially to the biceps femoris
- Covers the majority of the semimembranosus
Where is the semitendinosus muscle found?
- Origin: ischial tuberosity of the pelvis
- Attaches to the medial surface of the tibia
What are the actions of the semitendinosus muscle?
- Flexion of the leg at the knee joint
- Extension of thigh at the hip
- Medially rotates the thigh at the hip joint and the leg at the knee joint
What is the innervation of the semitendinosus?
Tibial nerve
Where is the semimembranosus muscle found?
- Located underneath the semitendinosus
- Origin: ischial tuberosity (but superiorly than the semitendinosus and biceps femoris)
- Attaches to the medial tibial condyle
What are the actions of the semimembranosus?
- Flexion of the leg at the knee joint
- Extension of the thigh at the hip joint
- Medial rotation of the thigh at the hip joint and the leg at the knee joint
What is the innervation of the semimembranosus?
Tibial nerve
What is a pulled hamstring?
Excessive stretch or tearing of the muscle fibres
- Often seen in athletes involved in running or kicking sports
- Damage to the muscle fibres is likely to rupture the surrounding blood vessels
- – Produces a haematoma
- – This is contained by the overlying fascia lata
How can you palpate the popliteal pulse?
A hard pulse to find
- Lies deep in the popliteal fossa so requires deep palpation to feel
- To make it easier, can ask patient to slightly flex their leg
- – This relaxes the fascia around the popliteal fossa
Describe patella dislocations
- Often happens during sports or dancing
- Mostly seen in teenagers
- Usually dislocates laterally
- More common in women
What is the popliteal fossa?
A diamond shaped area found on the posterior side of the knee
- The main path by which structures move from the thigh to the leg
What are the borders of the popliteal fossa?
- Superiomedial: Semimembranosus
- Superiolateral: biceps femoris
- Inferiomedial: medial head of gastrocnemius
- Inferiolateral: lateral head of gastrocnemius
- Floor: formed by the posterior surface of the knee joint capsule and the posterior surface of the femur
- Roof: made up of 2 layers: popliteal fascia, skin
What are the contents of the popliteal fossa?
Medial to lateral:
- Popliteal artery
- Popliteal vein
- Tibial nerve
- Common fibular nerve
- Small saphenous vein pierces the popliteal fascia of the popliteal fossa to enter the diamond and empty into the popliteal vein
What is the adductor hiatus?
Perforations in the adductor part of the adductor magnus
- The femoral artery and vein pass through it
What is the blood supply to the knee joint?
Popliteal artery branches to give: - Superior and inferior medial + lateral genicular arteries - Descending genicular artery - Middle genicular artery These anastomose around the knee
