Arthroscopy is a surgical procedure used to visualise and treat problems inside the knee joint without the need for a large incision. It's also known as 'keyhole surgery'—performed through 2-3 small incisions, each a few millimetres long, through which the surgeon inserts a miniature video camera and special instruments.
Images from inside the joint are transmitted in real-time to a screen, allowing for both precise diagnosis and effective treatment of injuries—all in the same surgical session.
The procedure lasts between 20 minutes and over an hour, depending on the complexity of the discovered lesions and the required manoeuvres. In most cases, the patient goes home the same day.
When is arthroscopy indicated?
Arthroscopy is recommended when the clinical examination and investigations (MRI, X-ray) indicate a problem inside the knee that can be resolved with this method.
Many of these injuries appear in active people, long before the age at which we usually talk about wear — see knee pain at a young age.
The most common indications are:
Meniscus Tears
Tears that cause pain, joint locking, or the sensation that the knee is 'giving way'. Depending on the type of tear, the meniscus can be repaired or partially removed. Partial meniscectomy remains one of the most common arthroscopic procedures worldwide.
Intra-articular loose bodies
Fragments of cartilage or bone floating in the joint, causing locking, sharp pain, and episodes of the knee 'catching'.
Ligament Injuries
Evaluation and, in some cases, reconstruction of the anterior cruciate ligament (ACL), which is frequently injured in sports accidents.
Synovitis
Inflammation of the synovial membrane, which can be evaluated and treated arthroscopically (biopsy, synovectomy).
Joint lavage
Removal of debris and inflammatory fluid from the joint, useful in certain clinical contexts.
What arthroscopy CANNOT fix
This is just as important to understand: arthroscopy does not cure osteoarthritis. If the joint is severely affected by osteoarthritis (stage III-IV), with destroyed cartilage and direct bone-on-bone contact, arthroscopy can, at best, temporarily relieve some mechanical symptoms (locking, sharp pain), but it does not address the underlying cause.
In advanced osteoarthritis, the reference treatment remains knee replacement. We always discuss this openly before surgery, so that every patient has realistic expectations.
Also, arthroscopy is not recommended as a routine procedure for 'cleaning out' an osteoarthritic knee—studies have shown that in the absence of a specific mechanical injury (torn meniscus, loose bodies), the benefit is limited.
Arthroscopy vs. traditional surgery — why minimally invasive?
Compared to open surgeries, arthroscopy offers significant advantages:
Reduced postoperative pain — incisions of a few millimetres versus 10-15 cm incisions
Considerably faster recovery — walking usually resumes the same day, and returning to normal activities is measured in weeks
Lower risk of infection — minimal tissue trauma
Almost invisible scars — much better cosmetic appearance
Usually same-day discharge
Precise diagnosis — direct visualisation can reveal lesions that imaging may miss
Diagnostic vs. Therapeutic Arthroscopy
Sometimes, investigations (MRI, X-ray) cannot accurately identify the cause of pain. Diagnostic arthroscopy allows the surgeon to directly view all knee structures—cartilage, meniscus, ligaments, synovium—and identify problems that other investigations might miss.
Most of the time, if a treatable lesion is discovered, it is addressed in the same surgical session—moving from diagnosis to treatment without a second intervention.
Risks and limits
Like any surgery, arthroscopy carries risks — rare for this procedure: infection (rare), thrombosis, joint stiffness, persistence of symptoms. Results vary from patient to patient.
The stiff knee: stiffness and arthroscopic arthrolysis
Stiffness means the knee no longer bends or straightens as it should. The movement stops earlier than expected, and the limit is felt as a hard block, not as pain alone.
It appears after operations — an anterior cruciate ligament reconstruction, a knee replacement — after fractures around the knee and after long periods of immobilisation. The cause is scar tissue inside and around the joint: arthrofibrosis. The tissue thickens, sticks to the surfaces that should glide and blocks the movement.
The first step is not surgery. Intensive physiotherapy comes first, guided and repeated, because scar tissue responds to movement while it is still young. In patients with a knee replacement, manipulation under anaesthesia can be added in the early window after the operation, while the tissue is still malleable. The literature describes this as a ladder: rehabilitation, then manipulation, then surgical release, in this order.
Arthroscopic arthrolysis is the surgical step of that ladder. Through the same small portals, the adhesions and the scar tissue that block the joint are released, and the recesses where the knee has lost its glide are freed. Arthrolysis is never a stand-alone act: it must be followed by early mobilisation and physiotherapy. Without them, the scar tissue reforms and the stiffness returns.
Honestly: not everyone regains full movement after an arthrolysis. The result depends on the cause of the stiffness, on how long it has been there and on the rehabilitation that follows. For a stiff knee replacement, arthroscopic arthrolysis is only one of the options — the decision is made case by case, after examination and imaging.
Arthroscopic synovectomy: when the synovial membrane is removed
The synovium is the thin membrane that lines the joint and produces the fluid which lubricates it. Normally it is discreet. It becomes the problem when it grows and inflames on its own account.
Three situations bring it into discussion: persistent synovitis, with fluid that returns again and again after aspiration; rheumatoid arthritis in which one knee remains inflamed despite treatment; and tenosynovial giant-cell tumour, also known as pigmented villonodular synovitis, a benign proliferation of the membrane that swells and destroys the joint from within.
Arthroscopic synovectomy removes the diseased membrane through the same small portals, under direct vision. Compared with open surgery it means less tissue trauma, less postoperative pain and an earlier start to movement — which matters, because a knee that is not moved after a synovectomy stiffens. Where it can be done arthroscopically, this is the preferred route.
The limit is the extent of the disease. In the diffuse form of tenosynovial giant-cell tumour, which spreads into all the recesses of the joint and sometimes beyond it, the choice between an arthroscopic and an open synovectomy depends on how far the tissue reaches. Sometimes the two are combined.
Honestly: recurrence exists, especially in the diffuse forms, and in rheumatoid arthritis the synovitis can return years later. That is why follow-up is part of the treatment, not something added afterwards — a synovectomy is judged over years, not over weeks.