Femur: The femur is classed as a long bone, only bone in the thigh, and the longest bone in the body. Its length varies from one-fourth to one-third of that of the body; The main function of the femur is to transmit forces from the tibia to the hip joint.
The femur is well covered with muscles so that only its superior and inferior ends are palpable.
Parts of the Femur
It can be divided into three areas; proximal end, shaft and the distal end.
The Proximal end consists of a head, neck, and two trochanters. The head faces superiorward, medialward, and slightly anteriorward. The proximal area of the femur forms the hip joint with the pelvis. There are also two bony ridges connecting the two trochanters.
Head – Connects with the acetabulum of the pelvis to make the hip joint. It has a glossy surface with a depression on the medial position; for the attachment of the ligament of head of the femur.
Neck – Attaches the head of the femur with the shaft. It is cylindrical, projecting in a superior and medial direction – this angle of projection permits for an enhanced range of movement at the hip joint.
Greater trochanter – A projection of bone that starts from the anterior aspect, just parallel to the neck. It is angled superiorly and posteriorly and can be found on both the anterior and posterior sides of the femur.
The site of attachment for the muscles gluteus medius, gluteus minimus, and piriformis.
Lesser trochanter – Shorter than the greater trochanter. It extends from the posteromedial side of the femur, just under to the neck-shaft junction.
Intertrochanteric line – A ridge of bone that runs in an inferomedial and connecting the two trochanters together. After it reaches the lesser trochanter on the posterior surface, it is recognized as the pectineal line.
Intertrochanteric crest – A ridge of bone that connects the two trochanters together. It is found on the posterior surface of the femur. There is a rounded tubercle on its superior half, this is designated the quadrate tubercle, where the quadratus femoris attaches. The distal fragment is pulled upwards and rotated laterally.
Shaft of the Femur
The shaft descends in a slight medial direction. This brings the knees closer to the body’s center of gravity, increasing stability.
On the posterior surface of the femoral shaft, a roughened ridges of bone, these are also described as the linea aspera.
Proximally, the medial border of the linea aspera fits the pectineal line. The lateral border enhances the gluteal tuberosity, where the gluteus maximus attaches.
Distally, the linea aspera increases and forms the floor of the popliteal fossa, the medial and lateral borders form the medial and lateral supracondylar lines. The medial supracondylar line stops at the adductor tubercle, where the adductor magnus muscle attaches.
The distal end is marked by the presence of the medial and lateral condyles, which join with the tibia and patella, forming the knee joint.
Medial and lateral condyles – Rounded areas at the end of the femur. The posterior and inferior surfaces connect with the tibia and menisci of the knee, while the anterior surface connects with the patella.
Medial and lateral epicondyles – Bony elevations on the non-articular areas of the condyles.
They are the area of attachment of some muscles and the collateral ligaments of the knee joint.
Intercondylar fossa – A depression found on the posterior surface of the femur, it lies in between the two condyles. It contains two facets for attachment of internal knee ligaments.
Facet for attachment of the posterior cruciate ligament – Found on the medial wall of the intercondylar fossa, it is a large rounded flat face, where the posterior cruciate ligament of the knee attaches.
Facet for attachment of anterior cruciate ligament – Found on the lateral wall of the intercondylar fossa, it is smaller than the facet on the medial wall and is where the anterior cruciate ligament of the knee attaches.
Muscles of the Femur
- Iliacus muscle Insert into the lesser trochanter of the femur.
- Psoas major muscle Insert into the lesser trochanter.
- Gluteus maximus muscle Insert into the gluteal tuberosity
- Gluteus medius muscle Insert into the lateral surface of the greater trochanter of the femur.
- Gluteus minimus muscle Insert into the forefront of the greater trochanter.
- Piriformis muscle Insert into the superior boundary of the greater trochanter.
Gemellus superior muscle Insert into the upper edge of Obturator internus’s tendon (indirectly greater trochanter).
- Obturator internus muscle Insert into the medial surface of the greater trochanter.
- Gemellus inferior muscle Insert into the lower edge of Obturator internus’s tendon (indirectly greater trochanter).
- Quadratus femoris muscle Insert into the intertrochanteric crest of the femur.
- Obturator externus muscle Insert into the trochanteric fossa.
- Pectineus muscle Insert into the pectineal line.
- Adductor longus muscle Insert into the medial ridge of linea aspera of the femur.
- Adductor brevis muscle Insert into the medial ridge of linea aspera.
- Adductor magnus muscle Insert into the medial ridge of linea aspera and the adductor tubercle of the femur.
- Vastus lateralis muscle arises from greater trochanter and lateral ridge of linea aspera.
- Vastus intermedius muscle arises from front and lateral surface of the femur.
- Vastus medialis muscle arises from the distal part of an intertrochanteric line and medial ridge of linea aspera of the femur.
- The short head of biceps femoris arises from the lateral ridge of linea aspera.
- Popliteus muscle arises from under the lateral epicondyle of the femur.
- Articularis genu muscle arises from lower 1/4 of anterior femur deep to vastus intermedius.
- Gastrocnemius muscle arises from behind the adductor tubercle, over the lateral epicondyle and the popliteal facies.
- Plantaris muscle arises from over the lateral condyle of the femur.
Articulations of the Femur
The proximal femoral head articulates with the acetabulum of the pelvis, forming a “ball-and-socket” joint. This formation allows for three planes movement at the hip joint: abduction and adduction in the frontal plane, flexion, and extension in the sagittal plane and internal and external rotation in the horizontal plane.
Distally, the femoral condyles of the femur articulate with the condyles of the tibia, making the tibiofemoral joint. Movement at the tibiofemoral joint happens in two planes: internal and external rotation in the horizontal plane, knee flexion, and extension in the sagittal plane.
The patellofemoral joint is made by the articulation of the patella with the intercondylar groove of the femur. Through flexion and extension of the knee joint, the articular surfaces of the patella and femur offer a sliding movement.
Ossification of the Femur
The femur ossifies from 5 centres: 1 primary and 4 secondary centres. The primary centre appears in the midshaft. 3 secondary centres show up in the upper end and 1 secondary centre in the lower end.
Primary centre appears in the mid shaft in 7th to 8th week of IUL.
The femoral head appears: 4-6 months
Greater trochanter appears: 2-4 years
Lesser trochanter appears: puberty
All of the femoral ossification centres fuse between the ages of 14 and 18 years.
Clinical Significance of the Femur
A femoral fracture that includes the femoral head, femoral neck or the shaft of the femur immediately below the lesser trochanter, particularly while linked with osteoporosis. Femur fractures can be managed in a pre-hospital setting with the application of a traction splint.
A stress fracture is known as the Femoral Stress fracture of the femur typically occurs over time with excessive weight bearing movement such as running, sprinting, jumping or dancing. A femoral stress fracture is a situation described by an incomplete crack in the femur.
Patellofemoral pain syndrome is a well-known sports-related injury that manifests as pain around or behind the patella. The cause of the condition is unclear, but genetic, neurologic, neuromuscular and biomechanical agents may contribute to its advancement.