Septic arthritis – causes, symptoms, diagnosis, treatment, pathology

Learning medicine is hard work! Osmosis makes it easy. It takes your lectures and notes to create
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much more. Try it free today! Septic arthritis, which is also called infectious
arthritis, refers to any joint inflammation caused by a microbe – and usually it results
from a bacterial infection of the joint. All types of joints; fibrous, cartilaginous,
and synovial joints can get infected. So let’s just use the synovial type as an
example. A synovial joint consists of a joint capsule
which has an outer fibrous layer, and an inner synovial membrane filled with synovial fluid. The synovial fluid is a clear viscous fluid
that looks like the white of an egg, and it helps lubricate the joint and absorb shock. The synovial membrane has blood vessels that
supply the joint with nutrients and oxygen. The tips of the bones that come together to
form the joints are covered by an articular cartilage, which is a slippery smooth layer
of cartilage that also absorbs shock and reduces friction during movement. Now, there are various ways that a bacterium
can get into your joint. First, it can be from a preexisting infection
in adjacent tissue, usually the bone, from where a bacterial infection can spread to
the articulating part of the bone and then makes its way right into the joint. It can also develop from hematogenous spread
which is where the bacteria is somewhere else in the body like the lungs, and then travels
through the bloodstream and gets into the joint. So, let’s say a child falls on some dirty
planks of wood and a nail pierces through their knee, infecting the synovial membrane
with bacteria. That bacteria could either come from the nail
and be living in the environment, like Clostridium tetani which causes tetanus, or it could be
bacteria that lives on the skin surface and gets shoved deep into the joint at the moment
that the skin is pierced, like Staphylococcus aureus. Once bacteria get into the synovial cavity,
they start destroying the articular cartilage with their toxins. One example of a toxin is chondrocyte proteases,
which are powerful enzymes that are capable of digesting the collagen in the articular
cartilage. Also, bacteria present with pathogen-associated
molecular patterns – or PAMPs, which is a group of bacterial surface antigens that
are recognized by your innate immune system as foreign, and result in the initiation of
an immune response. Macrophages can spot bacteria by their PAMPs,
they phagocytose them and at the same time release cytokines such as interleukin-1 and
tumor necrosis factor alpha -TNFα. These are signaling chemicals that recruit
more immune cells to the site of infection. Also, these PAMPs get recognized by mast cells
and they release histamine, which causes vasodilation and increases the vascular permeability. The final result is that more blood comes
into the area creating an inflammatory response, which makes the joint look red, swollen, and
warm. As more fluids leak out of the capillaries
and accumulate in the joint space, there’s an increase in the intra-articular pressure,
compressing and interrupting blood vessels supplying the joint. Eventually, this leads to necrosis of the
affected bones and cartilage, leading to joint destruction. People with septic arthritis develop joint
pain, impaired range of motion, and fever. But symptoms may differ according to the underlying
pathogen. Gonococcal arthritis which is caused by Neisseria
gonorrhoeae usually affects sexually active adolescents. The bacteria typically spreads hematogenously
and spreads from an initial infection of the cervix, urethra, or pharynx. Neisseria gonorrhoeae affects multiple joints,
and also causes multiple skin lesions and tenosynovitis which is inflammation of the
muscle tendons. Now, the majority of septic arthritis is not
due to Neisseria gonorrhoeae, and it’s called non-gonococcal arthritis. Non-gonococcal arthritis includes all of the
other pathogens, but most often, a single joint will be affected – typically a knee. Non-gonococcal arthritis is most often caused
by Staphylococcus aureus which can completely destroy the joint within days unless it’s
treated. Other bacterial causes include multiple Streptococcus
species, as well as Mycobacterium tuberculosis, and Borrelia species – which is the cause
of lyme disease. Diagnosis of septic arthritis starts with
obtaining synovial fluid from the joint, which is done by doing a joint aspiration – where
a needle is placed into the joint and fluid is aspirated or drawn out. That synovial fluid can be sent for analysis
– and typically there’s a high white blood cell count, positive gram stain, or a positive
culture – which identifies the exact cause. In addition, imaging in the form of an X-ray,
ultrasound, CT scan, or MRI can also be very useful in demonstrating bone erosion and joint
effusions especially for hip and sacroiliac joints, where synovial fluid aspiration is
difficult. Treatment of septic arthritis typically starts
with antibiotic therapy and pain medication. In addition, it may require joint aspiration
and washout, which can be done by a needle, a process called arthrocentesis. Alternatively it can be done by opening the
joint, a surgical operation known as arthrotomy. Alright, as a quick recap, in septic arthritis
there’s joint inflammation, which can be caused by various bacterial infections which
spread contiguously or hematogenously. The minority of the time, it’s caused by
Neisseria gonorrhoeae and it’s called gonococcol arthritis. But the majority of the time it’s caused
by Staphylococcus aureus or some other bacteria and it’s called non-gonococcol arthritis. Diagnosis requires getting a joint aspirate
and imaging and treatment includes antibiotics and surgical management.


  1. Another professional, enjoyable discourse with excellent diction and pronounciation of latin suffixes. Food for my hungry brain. Rgds 09AUG2018

  2. Oh hey, I'm 99% sure I had this. I never got a proper dx (of ANYTHING – heck, i never even got the hip in question aspirated for one, despite having a fever) though.
    The frustration of not knowing the answer to why I was in horrible pain for several weeks and movement impaired for a month after, plus my own curiosity, got me wanting to study medicine. Long story short, septic arthritis is probably why I'm watching this video in the first place!

  3. How can we forget mentioning ESR??
    It is a Surgical Emergency, Arthrotomy with open wash, Without waiting from dawn to dusk, or dusk to dawn if patient presented at night!

  4. I have an exam tomorrow.. and you guys just did the video of one of the topics I need to learn… DESTINY, I LOVE YOU ♡

  5. Septic arthritis is a medical emergency and needs emergent surgical intervention and antibiotics and hospitalization.

  6. Got this on my finger (septic arthritis), apparently its pretty rare but thankfully it wont affect my life too much

  7. Its a great page. I dont doubt that. But learning medicine implies more than a video. Medicine students just cant learn from this videos. They need real images, real cases, doses of treatment, and i repeat again real images. But its good anyway. Thank you for the video

  8. Is it adv for hijab ? In my country women must either cover their hair or go to a jail . I am sure their belief will be infected western countries . This is not freedom because if they will have power force all of you to cover your hair .

  9. I really like this arthritis treatment “Rοngοdο Ruzο” (Google it)! It will take out the pain and discomfort from my several years old arthritic hands and joints. I personally use this regularly particularly when the pain is too much, however I only need to spread enough of it on my hands to help make the pain go away fast. .

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