Stability of joints Flashcards
Give 3 factors that give joint stability
- Articular surfaces- The larger relative proportion of the two articulating surfaces, the more stable the joint e.g. in the hip, the acetabulum of the pelvis fully encompasses the femoral head.
- Ligaments-Prevent excessive movement which could damage the joint. The tighter ligaments are, the more stable the joint.
- Tone of surrounding muscles.
Name some conditions that affect the mobility of joints.
OA
RA
Sceptic arthritis
Pseudo-gout
Reactive arthritis
Describe the articular surfaces of the hip joint. How do they give stability?
The depth of the acetabulum is increased by the fibrocartilaginous acetabularlabrum & thetransverse acetabular ligament
- Over half of the head is encompassed by the acetabulum = increased stability.
Acetabular labrum:
- horseshoe shaped fibrocartilaginous ring
- increases depth
- larger articular surfaces
- improved stability
- Although the hip is a ball and socket joint which allows movement in all planes, as it’s a weight bearing joint, mobility is sacrificed for stability.
Describe how the ligaments give stability to the hip joint
The hip has extra-capsular ligaments that provide stability by reducing the range of motion - the hip can’t be extended far.
- Iliofemoral ligament- strongest
- Ischiofemoral ligament- weakest
- Pubofemoral ligament
- These ligaments spiral around the hip joint.
These ligaments are useful when standing because the hip muscles don’t have to work too hard = saves energy.
transverse acetabular ligament- makes up for weakness caused by fovea (the dent in the head of femur)
How do the muscles in the hip help provide stability?
Medial & lateral rotator muscles of the thigh pull the femoral head medially into the acetabulum.
Describe the articular surface of the knee joint. How does this provide stability?
modified hinge joint – hinge joint w/ a bit of rotation
Lateral condyle of femur is more raised than the larger medial condyle- prevents dislocation of the patella
vastus medialus- pulls patella medially to prevent dislocation
Describe the ligaments in the knee and explain how they give stability to the knee joint.
Medial collateral ligament
Lateral collateral ligament
Posterior cruciate ligament- strongest of the two cruciate ligaments, joining the femur & tibia- the main stabilising factor for the femur in the weight-bearing flexed knee
Anterior cruciate ligament- prevents displacement of femur
Posterior meniscofemoral ligament
oblique popliteal ligament:
- tendinous fibres go back diagonally to cross behind the knee joint
- from semimembranosus tendon
- crosses back up diagonally across the knee joint
- supports back of knee
Which are the most important muscles for stabilising the knee joint?
Quadriceps - particularly the vastus medialis & vastus lateralis muscles- help flex the knee
gluteal muscles important in positioning the knee – medius and minimus
What is the role of the meniscus in the knee joint?
Meniscus= cartilage
increases surface area of contact between femoral condyles and tibial plateau
spreads load
cushioning effect
Medial meniscus:
- tethered to medial collateral ligament and tibial plateau
- not mobile
lateral meniscus:
- free of lateral collateral ligament
- not tethered to tibial plateau
- mobile
NOTE- look at knee joint diagram on notes
How does the knee lock? What is the purpose of the knee locking?
Knee locking= rotational movement of femur on tibia
Due to shape of femoral condyles: medial condyle larger than lateral femoral condyle & lateral femoral condyle rotates medially during extension of knee – locks the knee
Function of knee locking:
- standing
- walking
- prevents having to use all muscles when standing straight – energy conserving
To unlock the knee: must laterally rotate using popliteus muscle
Describe the articular surface of the ankle joint. How does this provide stability?
Ankle joint= talocrural joint= hinge joint- has collateral ligaments to prevent adduction/ abduction
A deep socket is formed from the distal ends of the tibia and fibula into which the trochlea of the talusfits.
NOTE- look at diagram of ankle joint!
Describe the ligaments in the ankle. How do they provide stability?
Spreading of the tibia & fibula during dorsiflexion is limited by the strong interosseous tibiofibular ligament & the anterior & posterior tibiofibular ligament which attach the tibia & fibula together.
Unstable during plantarflexion.
Lateral support is provided by thelateral ligament of the ankle,&medially by themedial ligament of the ankle
Which muscles provide stability in the ankle & how?
During dorsiflexion (higher stability), movement is limitedby passiveresistance of the tibialis anterior muscle
What are the joints of the feet?
- Subtalar joint – saddle joint- between calcaneus & talus
- Talocalcaneonavicular joint- ball & socket joint- between talus, calcaneus & navicular
- mid tarsal joint – plane joint
- talus bone is wide anteriorly and narrow posteriorly – this increases stability
- when joint in extension, wider part of talus sits between tibia and fibular- close-packed joint – - when joint is in flexion, narrow part of talus between tibial and fibular- loose packed joint – less stable
NOTE- look at diagram of joint!
Describe the articular surfaces in the talocalcaneonavicular joint
Articular surfaces incompletely enclose the joint
Include:
- Anterior & middle inferior articular surfaces of the talus
- Anterior & middle superior articular surfaces of the calcaneus
- Articular surface of the head of the talus
- Posterior articular surface of the navicular bone
NOTE- look at diagram on notes of joint, ligaments etc!
