Joints

Question 1

Hip Joint

Answer 1

The hip joint is a synovial ball-and-socket joint between the femoral head and the acetabulum of the hip bone.

Mobility is assisted by the long femoral neck which laterally offsets the femoral shaft from the pelvis. As the neck is also narrower than the diameter of the head, considerable movement in all directions is possible before the femoral neck impinges on the acetabular labrum.

The articular surface in the acetabulum is horseshoe-shaped. The tips of the horseshoe are connected by a transverse ligament and the whole of the rim is augmented by a fibrocartilaginous labrum. The centre of the horseshoe is occupied by a ligament connecting the femoral head to the acetabulum: the ligament of the head of the femur or ligamentum teres

Question 2

Capsule of hip joint

Answer 2

The capsule is attached proximally around the acetabular labrum and transverse ligament, distally to the neck of the femur, anteriorly to the intertrochanteric line, and posteriorly attached halfway along the femoral neck, proximal to the trochanters. The capsule is extremely strong but is also loose to allow for movements of the hip. From the distal attachment, several fibres are reflected upwards as longitudinal bands (retinacular fibres) along the femoral neck to the articular margins of the head. These fibres support nutrient-carrying arteries from the trochanteric anastomosis, which extend along the femoral neck before supplying the main part of the head of the femur. The capsule is strengthened by three ligaments: the iliofemoral, ischiofemoral and pubofemoral ligaments. The iliofemoral ligament is shaped in the form of an inverted ‘Y’, with the stem arising from the anterior inferior iliac spine and the acetabular rim, and the two limbs of the ‘Y’ diverging to be attached to the upper and lower ends of the intertrochanteric line. It is the strongest ligament of the three and prevents hyperextension.

Question 3

Which muscles adduct the hip?

Answer 3

Pectineus, adductors longus, brevis and magnus, and gracilis

Question 4

Which muscles abduct the hip?

Answer 4

Gluteus medius and minimus

Question 5

Which muscles medially rotate the hip?

Answer 5

The anterior fibres of gluteus medius and minimus

Question 6

Which muscles laterally rotate the hip?

Answer 6

Mainly gluteus maximus.

Supported by posterior fibres of gluteus medius and maximus, Obturator internus and externus, quadratus femoris, the gemelli and piriformis

Question 7

Which muscles flex the hip?

Answer 7

Psoas major and iliacus, assisted by rectus femoris, tensor fasciae latae, sartorius and pectineus

Question 8

Which muscles extend the hip?

Answer 8

Gluteus maximus and the hamstrings

Question 9

The knee joint

Answer 9

This is a synovial complex hinge joint that allows flexion and extension, with some rotation in flexion. The femoral condyles articulate with the tibial condyles, and the patella articulates with the anterior surface of the distal femur.

The femoral condyles are convex while the tibial condyles are flat. The tibial surfaces are made concave by fibrocartilaginous menisci, one lateral and one medial, which are circumferentially attached to the capsule. Popliteus is attached by fibres into the lateral meniscus, and laterally by a tendon passing through the capsule to the lateral femoral condyle

Question 10

Capsule of the knee joint

Answer 10

The capsule is deficient anteriorly and is completed by the quadriceps tendon. At its medial and lateral aspects the capsule is reinforced by retinacular fibres originating at the vasti medialis and lateralis. The synovial membrane extends superiorly as the suprapatellar bursa or pouch

Question 11

Collateral ligaments of the knee joint

Answer 11

Medial:
Flat ligament attached to the distal femur at the capsule and medial meniscus inferior to the adductor tubercle and travelling downwards and forwards to insert onto the medial tibia above and behind the pes anserinus

Lateral:
Cord like and free from the capsule. It is attached to the lateral femur above the groove for popliteus tendon and runs downwards and backwards to insert onto a depression in the lateral aspect of the head of the fibula

Question 12

Cruciate ligaments of the knee

Answer 12

Anterior:
Connects intercondylar eminence to the posteromedial aspect of the lateral femoral condyle, preventing backward displacement

Posterior:
Connects the intecondylar eminence to the anterolateral aspect of the medial femoral condyle preventing forward displacement

Question 13

Which muscle(s) medially rotate the flexed knee?

Answer 13

Semimembranosus and semitendinosus

Question 14

Which muscle(s) laterally rotate the flexed knee?

Answer 14

Biceps femoris

Question 15

Which muscles flex the knee?

Answer 15

Initiated by popliteus, which rotates the femur laterally on the tibia, thus “unlocking” the knee

Hamstrings are the main flexors

Question 16

Tibiofibular joints

Answer 16

The superior and inferior tibiofibular joints provide stability for the ankle during weight-bearing and locomotion. The former is a small synovial joint between a facet on the lateral tibial condyle and a corresponding facet on the fibular head. There is a capsule with anterior and posterior ligaments. Movement is limited to a small degree of axial rotation of the fibula.

The inferior joint is a fibrous joint (syndesmosis) with the opposing rough surfaces of the bones connected by a strong interosseous ligament and augmented by anterior and posterior tibiofibular ligaments. These allow slight distraction of the tibia from the fibula during dorsiflexion of the ankle, when the wider anterior body of the talus comes between them

Question 17

Ankle joint

Answer 17

This is a synovial hinge joint with a deep mortise formed by the distal tibia and fibula to house the body of the talus. Its stability is as dependent on the ligaments that hold the tibia and fibula together as on the collateral ligaments that keep the talus contained within the mortise.

The upper aspect of the talus articulates with the tibia. The medial surface of the body of the talus articulates with the medial malleolus, and the lateral surface of the body of the talus articulates with the medial articular surface of the distal fibula.

Movements are flexion (plantarflexion) and extension (dorsiflexion). The malleoli prevent inversion or eversion from occurring at the ankle joint

Question 18

Which muscles are responsible for plantarflexion?

Answer 18

Soleus, gastrocnemius and plantaris

Question 19

Which muscles are responsible for dorsiflexion?

Answer 19

Tibialis anterior

Question 20

Subtalar joint

Answer 20

Inversion and eversion of the foot occur at the subtalar joint, a composite of the posterior talocalcaneal and the talocalcaneonavicular joints, which function as one joint. The former is an articulation between the bodies of the talus and calcaneus, while the latter consists of the convex head of the talus and a concave socket formed by the calcaneus, navicular and ligaments. The foot is inverted and everted by approximate ball-and-socket movements round the head of the talus at the talocalcaneonavicular joint, with gliding movements in the posterior talocalcaneal joint