Knee Surgery… there’s an app for that!


Nowadays “there’s an app for that” could be the 11th Commandment … there is a bunch of apps for everything, even for the most stupid daily activities.

vks1A friend of mine told me to have a look at this one: Virtual Knee Surgery. It is a very realistic game that follows all the basic steps of a Total Knee Replacement surgery. The user is invited to interact with the surgeon in order to perform the necessary operations.

After living this experience in a real operating room, personally I’ve found this app a really nice and clear explanation 🙂 If you want to spend ten minutes to learn the basics of TKR, I definitely can say it’s worth it!


Mallet Finger: don’t try this at home

There are a few everyday life experiences that everybody is destined to go through every now and then. Like correctly plugging a USB device only at the third attempt (despite there are only two possibilities), or directly setting the alarm clock half an hour earlier because we know we’re used to putting it off at least four times, or having Mallet Finger.

Mallet Finger is probably one of the most painful and annoying injuries of all time. Technically, it is an injury of the extensor digitorum tendon of the fingers at the distal interphalangeal joint (DIP). In more simple terms, it is the typical injury that occurs when we play basketball and the ball suddenly hits our extended finger. Besides the immediate sensation of pain, within a few minutes our finger will start swelling and we won’t be able to straighten it for a while. We then leave the court with an awesome facial expression (it really hurts, you all know…), but do we know what happened inside our finger?

mallet finger The distal interphalangeal joint (DIP) hinge jointof the hand is nothing more than a hinge joint between the two last phalanges of the finger. This kind of joint only admits one degree of freedom, which is the rotation about the joint axis. As a result, our phalanges are allowed to make flexion and extension movements. Thus, the DIP is the last joint of the finger. A sudden high force acting at the tip of the finger (the ball we were trying to catch) strongly solicits the thin DIP extensor tendon. In case of rupture, or tearing, of this tendon from the bone, the finger usually gets painful, swollen, and bruised. Occasionally, blood can collect beneath the nail. In the worst case, the force of the blow may even pull away a piece of bone along with the tendon. mallet finger bruised The loss of extensor tendon continuity might lead to severe consequences and must be carefully treated. In a first moment, ice should be immediately applied and the hand should be elevated above the level of the heart. Medical attention should be sought within a week after injury. Most mallet finger injuries can be treated without surgery. fingertip splintsNormally, X-rays are necessary in order to look for potential bone fractures or joint misalignment. The presence of blood beneath the nail and nail detachment may be a sign of nail bed laceration or open (compound) fracture. A splint can be applied to hold the fingertip straight (in extension) until it heals (8 weeks full-time, 3-4 further weeks less frequently). With this treatment plan, the finger usually regains an acceptable function and appearance. Despite that, it is not guaranteed that the patient will be able to regain full fingertip extension.

If nonsurgical treatment fails, after mallet finger surgeryconsultation with an orthopaedic surgeon the patient may consider to resort to surgical repair. In case of very severe deformity or inability to properly use the injured finger, surgery is done to repair the fracture using pins, pins and wire, or even small screws. Surgical treatment of the damaged tendon can include tightening the stretched tendon tissue, using tendon grafts, or even fusing the joint straight.


sources: mainly this website and this website, and then Google Images

the Ankle Joint: some hints

The ankle is the region where the foot and the leg meet. The ankle joint is actually composed by three smaller joints:

  1. the ankle joint proper, commonly called ankle mortise joint (but also talocrural joint).  It is a synovial hinge joint that connects the distal ends of both the tibia and the fibula in the lower limb with the proximal end of the talus.
  2. the subtalar joint, that occurs at the meeting point of the talus and the calcaneus.
  3. the inferior tibiofibular joint, between the fibula and the tibia. More precisely, it is formed by the rough, convex surface of the medial side of the distal end of the fibula, and a (corresponding) rough concave surface on the lateral side of the tibia.

ankle joint and its three sub-joints

The boney architecture of the ankle consists of three bones: the tibia, the fibula (in the leg) and the talus (in the foot). The talus is also called the ankle bone since it’s the most important bone in the ankle articulation. In normal health conditions, the articulation between the tibia and the talus (ankle mortise joint) bears the greatest part of body weight: it is the region where ankle efforts are mostly concentrated.

The medial malleolus is a boney processmalleoli extending distally off the medial tibia. There is also a lateral malleolus, generated by a distal-most aspect of the fibula. Together, the two malleoli, along with their supporting ligaments, stabilize the talus underneath the tibia.

The ankle joint is bound by the strong deltoid ligament (it is attached at the medial malleolus of the tibia and supports the medial side of the whole joint) and three lateral ligaments: the anterior and posterior talofibular ligaments (they support the lateral side of the joint, from the lateral malleolus to the dorsal and ventral ends of the talus) and the calcaneofibular ligament (it is attached at the lateral malleolus and to the lateral surface of the calcaneus).

ankle ligaments

Achille's tendonThe calcaneus is also attached to the Achille’s tendon (also known as the calcaneal tendon or the tendo calcaneus), that is a tendonous extension of gastrocnemius and soleus muscles of the leg. It attaches the heel to the posterior leg.

Concerning the joint motion, the ankle joint theoretically admits 1 degree of freedom: movements of plantar flexion and dorsiflexion.

ankle motions

In addition to these, the geometry of the different bones that form the articulation permits other more limited movements, such as foot eversion and inversion.

sources: Wikipedia and this website

the Knee Bursae: some hints

The bursae of the knee can be defined in a very simple way: they are fluid sacs, or synovial pockets. This second definition comes from the sinovial fluid that fills them.

Synovial fluid is made of hyaluronic acid and lubricin, proteinases and collagenases. Its main functions are reducing friction by lubricating the joint, absorbing shocks and properly “feeding” joint cartilage. In the case of the knee, the Knee Capsule encloses the Knee Cavity which is filled with synovial fluid. Knee Bursae surround and sometimes communicate with the Knee Cavity, as we can see in the picture.

Usually Knee Bursae are thin-walled and represent the weak point of the joint. At the same time, their presence is really important since they enlarge the joint space. They can be grouped according to:

  • their characterization as communicating and non-communicating bursae. A communicating bursa is when a bursa is located adjacent to a joint, thus having the synovial membrane in communication with the joint itself.
  • their location (frontal, lateral, medial).

In pathological conditions, such as excessive local friction, infection, arthritides or direct trauma, fluid and debris collect within the bursa or fluid extends into the bursa from the adjacent joint. As a consequence, the walls of the bursa thicken as the bursal inflammation becomes longstanding. The term bursitis refers to pathological enlargement of the bursa. Clinically, bursitis mimics several peripheral joint and muscle abnormalities.


<–prepatellar bursitis

          elbow bursitis–>



sources: Wikipedia and this website

Patellar Reflex

definition _

Patellar Reflex, also called knee-jerk, is a stretch reflex associated with quadriceps femoris muscle stretching.

how it works _

The stretch is created by a blow upon the patellar tendon (positioned just below the Patella). This blow, usually performed with a specific tendon hammer, activates the muscle spindle in the quadriceps femoris muscle.

Muscle spindle is a particular type of sensory receptor, normally embedded in muscle fibers, able to detect changes in the length of the muscle itself. Once “activated” by the external blow, this receptor sends a signal to the spinal cord. Instead of involving higher nervous centres (it would take too long), at the level of the spinal cord an alpha-motor neuron is immediately activated.

The alpha-motor neuron conducts an efferent impulse directly back to the quadriceps femoris muscle, leading to its contraction. At the same time, an inhibitory interneuron relaxes the hamstring muscle, which is the quadricep’s antagonistic muscle.

The result of such coordinated contraction-relaxation, causes the “kick movement” of the leg. In normal health conditions, the leg extends once and then comes back to rest. It only takes about 50 milliseconds between the tap and the start of the leg kick.

why it is useful _

Patellar Reflex is a proprioceptive reflex which helps keeping posture and balance. The fact that everything “happens” at the level of the spinal cord, without involving higher nervous centres, allows for instance to keep balance without effort (actually, one does not have to focus on keeping an upright position). Energies are saved for more complex activities. Moreover, Patellar Reflex helps avoiding strong muscle contractions which could tear the tendon.

clinical interest _

As said, there is no interneuron in the pathway leading to contraction of the quadriceps muscle. Patellar Reflex can be used, for example, to check the conditions of the connections between the spinal cord and the muscles.

The absence or decrease of the Patellar Reflex is known as Westphal’s sign. On the other hand, multiple oscillation of the leg following the blow may be a symptom of cerebellar diseases.

source: contents taken from Wikipedia’s page

the Patella: some hints

The patella (also known as knee cap) is a thick, circular-triangular bone which articulates with the femur and covers and protects the anterior articular surface of the knee joint.

It is the largest sesamoid bone in the human body. In the adult the articular surface is about 12 cm2 and covered by cartilage, which can reach a maximal thickness of 6 mm in the centre at about 30 years of age.

The patella is attached to the Quadriceps tendon (of the quadriceps femoris muscle), which contracts to extend/straighten the knee. The vastus lateralis and vastus medialis are attached to lateral and medial borders of patella respectively. The vastus intermedialis muscle, not showed in this picture, is attached to the base of patella.

The patella is stabilized by the insertion of vastus medialis and the prominence of the anterior femoral condyles, which prevent lateral dislocation during flexion. The retinacular fibres of the patella also stabilize it during exercise.

The primary functional role of the patella is knee extension. The patella increases the leverage that the Quadriceps tendon can exert on the femur by increasing the angle at which it acts.

Patellar problems are among the most common causes of knee pain. This disease may be associated with other symptoms, such as instability or giveaway, dislocation, catching, grinding (crepitation), and/or swelling. These symptoms may present spontaneously or following injury (such as subluxations, blows to the front of the knee etc.). In general terms, patellar problems can be organized as:

  1. Pain alone – “patellofemoral syndrome”,
  2. Pain from malalignment – tilt and/or displacement,
  3. Instability – subluxation and dislocation,
  4. “Wear and tear” – arthritis,
  5. Other problems – synovial plica, tendonitis, bursitis, Osgood Schlatter’s disease, etc.

Surgery is rarely necessary, and must be carefully considered. For example, for the “pain alone” case, surgery is rarely indicated since it may even make pain worse. In these terms, surgery is best used as a last resort, after all other techniques fail (normally: conservative care trials).

Arthroscopy is the very best way to evaluate the patella and surrounding portions of the knee joint. Surgery will vary depending upon the type of patellar problem.  Of course it has risks, such as infection, stiffness, continued instability, weakness, pain, blood clots, fracture, impaired bone healing, etc. Recovery ranges from 6 weeks to 6 months, or even longer, depending upon the type of surgery, healing rates and limitations, and patient rehabilitation and efforts.

sources: two websites, this one and this one

Knee Alignment Conditions

The lower limb Mechanical Axis is defined by a line running through the centre of the hip joint to the centre of the ankle joint.  This line should pass essentially through the centre of the knee joint.

The tangential distance of this line from the centre of the knee joint is referred to as the Mechanical Axis Deviation.

In a Varus knee, the axis passes through the knee medial compartment, while in a Valgus knee it crosses the knee lateral side.

Another key concept is the one of Anatomical Axis. The Anatomical Axis of a bone is represented by a line drawn down the centre of the medullary cavity of the bone.

In the femur, the mechanical and anatomical axes deviate whereas in the tibia the mechanical and anatomical axes are essentially represented by the same line.

The angle between the Anatomical Axis of the femur and the lower limb Mechanical Axis is normally 6° of Valgus.

source: this website

A day at the hospital

Last week I was invited to attend in a knee surgery at the Hospital Cavale Blanche, in Brest. For my PhD project, the research work that I am currently carrying on is actually closer to the mechanical side of Robotics (microactuators, tiny mechanical structures, wireless energy transfer techniques …). Although, since one of my supervisors is an orthopedic surgeon, I was invited to participate to TKA surgery. Basically, this meant two things: I had to put on specific sterilized clothes and, once in the operating room, I was allowed to watch and put questions 🙂

When I got here I was told that, for PhD students in the field of Robotic Surgery, half a day at the hospital was more useful, in terms of acquirable knowledge, than a month of theoretical study. Actually, one of the aspects I mostly appreciated was the “pedagogical approach” of the surgeon towards the observers. We were two, a sweet girl who’s completing her studies in Pharmacology and me. And the surgeon kept explaining each single step, motivating each procedure and answering all our questions. The confidence he showed while (literally) manipulating the patient’s knee and conducting the operation in front of younger and less experienced surgeons was simply amazing.

Before the surgery, the patient can decide to undergo either general or local anesthesia. Let’s say that the noises and, especially, the smells produced by hammers and saws are not the best way to stimulate one’s appetite 😉 But one thing is sure: after living the atmosphere of such a delicate surgical operation, and understanding that one can really trust expert surgeons, personally I wouldn’t be so worried/scared to undergo TKA as I was before 🙂

the Meniscus: some hints

Medically speaking, the “cartilage” is actually known as the meniscus. The meniscus is a C-shaped piece of fibrocartilage which is located at the peripheral aspect of the joint. The majority of the meniscus has no blood supply. For that reason, when damaged, the meniscus is unable to undergo the normal healing process that occurs in most of the rest of the body. In addition, with age, the meniscus begins to deteriorate, often developing degenerative tears. Typically, when the meniscus is damaged, the torn piece begins to move in an abnormal fashion inside the joint.

Because the space between the bones of the joint is very small, as the abnormally mobile piece of meniscal tissue (meniscal fragment) moves, it may become caught between the bones of the joint (femur and tibia). When this happens, the knee becomes painful, swollen, and difficult to move.

The meniscus has several functions:

  • Stability – As secondary stabilizers, the intact meniscii interact with the stabilizing function of the ligaments and are most effective when the surrounding ligaments are intact.
  • Lubrication and nutrition – The meniscii act as spacers between the femur and the tibia. By doing so, they prevent friction between these two bones and allow for the diffusion of the normal joint fluid and its nutrients into the tissue which covers the end of the bone. This tissue is known as articular cartilage. Maintenance of the integrity of the articular cartilage is critical to preventing the development of post-traumatic or degenerative arthritis.
  • Shock absorption – The biconcave C-shaped pieces of tissue known as meniscii (cartilage in non-medical terms) lower the stress applied to the articular cartilage, and thereby have a role in preventing the development of degenerative arthritis.

source: this website