The fibula is one of your leg bones, sitting on the outside of your tibia (shin bone) and as noted yesterday, in Day 1 of fun skeletal facts, helps forms the ankle joint. Also, a quick note regarding anatomical terminology before we continue, ‘the leg’ anatomically only consists of the part of your lower extremity below the knee, with your tibia and fibula, while above the knee is your thigh. The fibula’s primary functions include its contribution to the ankle joint as well a site of muscle and ligament attachments. It is essentially a non-weight bearing bone – which is why some people may still be able to walk with a broken leg. A study from 1984 using six amputated lower limbs (yes, really), found that the fibula bore 6.4% of the compression load applied when the ankle was in the neutral position (standing). With the ankle in dorsiflexion (foot/toes toward the shin, like when you initiate walking with a heel strike) the load on the fibula increased slightly and then in plantarflexion (toes pointed down, weight on the ball of your foot), the fibular load decreased (Takebe et al. 1984). Due to this minimal role in weight bearing, the fibula is a candidate for bone grafting, the process of repairing complex or incompletely healed fractures with other bone.
Compared to the tibia, the fibula is quite small and thin – honestly, it looks like a stick. The word fibula is derived from the Latin word for “brooch”. The fibula is also sometimes referred to as the peroneal bone, peroneal from the Greek meaning “clasp”. This bone is so named because it resembles the pin part of a brooch, the part that clasps into the tibia. Due to the minimal role it has in weight bearing, the fibula in some animals no longer articulates with the tarsals (ankle) and becomes fused to the tibia, as you can see in the image below which illustrates the skeletal anatomy of a horse leg.
And that wraps up our quick overview of the fibula – there will be more headed your way tomorrow when we discuss the tibia, including ways that it contributes to music in the archaeological record.
REFERENCES & MORE TO EXPLORE
Anatomy, Bony Pelvis and Lower Limb, Fibula. Gupton et al. NCBI. Last updated 16 Aug 2020
Anatomical Terms of Movement. Teach Me Anatomy Series. 2020
Role of Fibula in Weight Bearing. Takebe et al. Clinical Orthopaedics and Related Research. 1984
Check out this article for more great illustrations of fused tibia/fibula combos -> A Comparative Study of the Inferior Tibio-Fibular Joint. Carelton. Department of Anatomy, University of Oxford. 1941.