Overview
The femur is the longest bone of the cat. It forms the skeleton of the thigh and transmits the thrust of the pelvic limbs, which in the cat power the jump. It articulates at the hip with the acetabulum and at the stifle (articulatio genus) with the tibia and patella. In the cat it is long, slender and fairly straight.
Proximal end
- Head (caput ossis femoris): spherical, sits in the acetabulum. The fovea of the head receives the ligament of the femoral head.
- Neck (collum ossis femoris): joins the head to the shaft.
- Capital physis: the growth plate between the head and the neck; in cats neutered early it closes later.
- Greater trochanter: lateral, insertion of the gluteal muscles; palpable.
- Lesser trochanter: medial, insertion of the iliopsoas.
- Trochanteric fossa: between the greater trochanter and the neck; entry point for intramedullary pins and for bone marrow aspiration.
Shaft
The diaphysis is cylindrical. On its caudal surface the facies aspera, bounded by medial and lateral lips, receives the adductor muscles.
Distal end
- Trochlea: cranial groove in which the patella glides.
- Medial and lateral condyles: caudal articular surfaces in contact with the menisci and tibia.
- Intercondylar fossa: houses the cruciate ligaments.
- Sesamoid bones: two fabellae in the heads of origin of the gastrocnemius and a small sesamoid in the tendon of the popliteus; all visible on a lateral stifle radiograph.
Clinical relevance
- Femoral capital physeal dysplasia: spontaneous separation, without trauma, of the femoral head through the capital physis. It affects young cats, mainly overweight neutered males, and is sometimes bilateral.
- Femoral fractures: common after trauma; diaphyseal fractures are often comminuted.
- Hip dysplasia and patellar luxation (shallow trochlea), often found together in the cat.
- Osteosarcoma: the distal femur is one of the most frequent appendicular sites of feline osteosarcoma, which metastasises less than in the dog.