Next Lesson - Conditions of the Knee
Core
Want more information on anatomy before you begin looking at conditions? Head to our articles on Bones of the Lower Limb and Muscles of the Lower Leg.
A tibial plateau fracture is a fracture to the articulating surface of the tibia (the joint surface at the top of the bone, where it meets the thigh bone in the knee joint). The top of the tibia has two rounded ends called condyles (medial and lateral). The fracture can be unicondylar (one condyle) or bicondylar (both), but it is the lateral tibial condyle (on the outer side of the knee) that is most commonly affected. The injury usually occurs due to a varus or valgus load on the knee joint (a sideways force that pushes the knee outwards, varus, or inwards, valgus). Tibial plateau fractures present with sudden pain, swelling of the knee, difficulty bearing weight and reduced movement of the knee joint. This injury can be associated with tears of the anterior cruciate ligament (ACL, a strong ligament inside the knee) or the menisci (the C-shaped pads of cartilage that cushion the knee). In more severe injuries, complications may include damage to the popliteal artery (the artery behind the knee) or the tibial or common peroneal/fibular nerve, and compartment syndrome (see below). Diagnosis is initially made with an X-ray, with CT often used to further define the fracture pattern. Treatment depends on the injury. A small fracture that has barely moved, with no ligament or other injury, can be treated without surgery, using a hinged knee brace (a brace that lets the knee bend in a controlled way) and limited weight-bearing. Most other tibial plateau fractures need review by an orthopaedic surgeon and usually surgery to restore the joint surface and keep the knee stable.
Image - X-ray Showing a Tibial Plateau Fracture
Creative commons source by James Heilman, MD [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
Compartment syndrome is increased pressure in a compartment (a group of muscles with their blood vessels and nerves, enclosed by a tough sheet of tissue called fascia). The raised pressure restricts the blood supply and can damage the muscles and nerves. It commonly occurs in the lower leg. It presents with severe limb pain that is out of proportion to the injury, deep, poorly localised, not relieved by analgesia (painkillers) and worsened by passive stretch (when someone else moves the muscle to stretch it). The limb is swollen and firm, with shiny skin over the compartment. As the ischaemia (poor blood supply) continues, it damages the nerves, causing paraesthesia (altered sensation, such as pins and needles or numbness) and then paralysis. These are late signs, so treatment should not wait for them. Any tight dressings, bandages or casts are released straight away. If compartment syndrome is confirmed, treatment is an urgent fasciotomy (a surgical procedure where the affected compartments are cut open to relieve the pressure) to prevent permanent damage to the muscles and nerves. The wound is usually closed later, sometimes with a skin graft (skin taken from another part of the body to cover the wound). If compartment syndrome is not treated, the muscle can die (necrosis) and the limb may need to be amputated. Other complications include rhabdomyolysis (breakdown of damaged muscle), which can lead to kidney failure.
Image - Surgical Fasciotomy
Creative commons source by آرمین [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
Common Peroneal/Fibular Nerve Injury
Injury to the peroneal/fibular nerve is relatively common: it is the most commonly injured nerve of the lower limb after trauma. The nerve winds round the neck of the fibula (the thin bone on the outer side of the lower leg), just under the skin, so a fracture there, a tight plaster cast or other pressure can injure it. The common peroneal nerve is a branch of the sciatic nerve that arises in the popliteal fossa (the hollow behind the knee). It supplies motor innervation (nerve supply to muscles) to the lateral and anterior compartments of the leg and to the short head of the biceps femoris (a muscle at the back of the thigh). It supplies sensory innervation (nerve supply to the skin) to the anterolateral (front and outer) leg and the dorsum (top) of the foot. This injury presents with foot drop: the patient cannot lift the front of the foot (dorsiflexion), so the foot drops downwards (plantarflexion) and the toes drag when walking. To clear the ground the patient lifts the knee high (a steppage gait). The ankle may also be inverted (turned inwards) because eversion (turning the sole outwards) is weak. There is also paraesthesia of the anterolateral leg and dorsum of the foot.
Injury to the tibial nerve is relatively uncommon (compared to injury to the common peroneal nerve). The tibial nerve is a branch of the sciatic nerve that arises in the popliteal fossa. It supplies motor innervation to the posterior compartment of the leg and sensory innervation to the posterolateral (back and outer) side of the leg, the lateral side of the foot and the sole of the foot. Therefore, when injured, the typical features include calcaneovalgus posture (the foot is pulled up towards the shin and turned outwards), inability to stand on tiptoe (due to paralysis of the calf muscles at the back of the leg) and loss of sensation in the areas listed above.
Reviewed by: Dr. Marcus Judge
Edited by: Dr. Maddie Swannack- 7068
