Knee Symptoms

There are only a relatively limited number of symptoms can arise in a knee, and these include:-




Pain is the most common and most prominent symptom in someone presenting with a knee problem. ‘Knee pain’ is such a broad and generic thing that straight away your GP / physio /knee surgeon will ask you many questions to clarify the exact nature of your knee pain:-

- Was there any specific injury/trauma and how quickly did your pain come on?

  • A history of knee pain with a specific injury or accident, such as if the knee twists during a football tackle or from a ski fall, is a clear and obvious indicator that something inside the knee joint might be damaged, such as a ligament or cartilage tear.
  • A lack of any specific episode of trauma implies that the knee pain might be due to an inflammatory problem or a degenerative process in the joint.
  • Knee pain that comes on quickly or suddenly (either with or without any actual trauma/injury) is more likely to be from something specifically tearing inside the joint.
  • Knee pain that comes on gradually (particularly without any specific trauma) is more likely to be inflammatory or degenerative in origin.

- Can you localise where the actual pain is?

  • If your knee pain is localized to one specific spot or area then this can be very useful indeed in narrowing down a specific diagnosis. If you know your surface anatomy then it’s easy to correlate the location of a specific pain to a particular (or list of particular) anatomical structure(s): e.g. pain just below the kneecap is often due to patellar tendonitis or fat pad inflammation. [See the ‘Where’s your knee pain?’ section on our website.]
  • If your knee pain is more ‘general’ (not being localized to one specific slot and being more widespread), then this can imply that there might be a generalized inflammatory problem with the knee or more widespread degeneration.

- Is it a sharp and sudden pain or more of a constant pain?

  • Sharp sudden knee pain implies that there might be something torn or damaged inside the knee, and/or something catching, e.g. a meniscal cartilage tear.
  • Constant pain in the knee, even at rest, implies that there might be either inflammation, possible infection (if the knee pain is very severe and the joint is hot, red and swollen) or degeneration/arthritis.

- Does your pain come on specifically during exercise?

  • If your knee feels fine when you first start exercise, particularly running, but then you develop knee pain that comes on after a certain distance or time, then this implies that something might be rubbing inside your knee and becoming inflamed.
  • If this kind of pain is felt at the front of the knee, just below the kneecap, then it might be due to patellar tendonitis or fat pad inflammation.
  • If the pain is around the outer (lateral) side of the knee, then the cause might be Iliotibial Band (ITB) Friction Syndrome.
  • If the pain is felt around the front of the knee, around the inner (medial) border of the kneecap, then this could be Medial Plica Syndrome.

- Do you get pain at the front of the knee with stairs / squatting / sitting?

  • If so then this implies that your pain might be coming from your patellofemoral joint (from the surface of the back of the kneecap).

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Clicking in a knee joint is very common indeed. Painless clicking is rarely of any importance or concern - most of the time we never really know or find out exactly what the cause of the clicking might be, although commonly it tends to be due to either catching of soft tissues from the lining of the knee or crunching noises can come from rough articular cartilage surfaces on the inside of the knee (particularly on the back of the kneecap).

Painful clicking, however, is important, particularly if it is associated with feelings of catching, giving way or locking – as this implies that there might be something torn, unstable or loose in the knee, getting caught or pinched as the knee moves.


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Catching or giving way are what we refer to as ‘mechanical’ symptoms. There are two different broad categories of giving way of the knee:-

  1. If the knee feels relatively OK most of the time, but intermittently something catches in the knee, there is sharp pain and the knee either gives way or feels like it might give way, then this implies that there is something torn and either unstable or loose in the knee, that is intermittently catching. With a meniscal cartilage tear, patients tend to get painful giving way particularly with things like squatting or twisting on the knee. Giving way because of a loose body in the knee (a loose piece of bone or cartilage) tends to be more ‘random’ and sometimes less painful.
  2. If the knee feels generally wobbly and unstable, and the joint gives way intermittently, sometimes without any particular pain, then this implies instability secondary to ligament damage, such as an ACL tear. With ligamentous instability, people are sometimes fine running in a straight line, but they have problems (and sometimes giving way) particular if they try to turn or pivot on the knee.

If a knee joint is giving way then this is a significant issue. If you just leave a functionally unstable knee alone, then every time the joint gives way there is the risk of further damage being caused inside the knee (particularly to the meniscal cartilages and the articular cartilage surfaces). In addition, there is is the risk of someone really hurting themselves if their knee gives way at an inopportune moment (e.g. coming down an escalator). Therefore, depending on the patient’s fitness and aspirations, significant functional instability in a knee really does need to be taken seriously and treated properly, in a timely fashion, and not just treated as a low priority and left alone.


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Proper locking of a knee joint is where you try and straighten the knee but then something catches inside the joint, preventing the knee from straightening out fully.

The two most common causes for locking of a knee are:-

  1.  a locked, displaced, bucket-handle tear of a meniscal cartilage, and 
  2. a loose body (a detached piece of bone or cartilage) getting stuck in the joint.

If a knee is locked after some kind of trauma, such as a twisting or squatting injury, then one has to assume until proven otherwise that this is a displaced bucket-handle meniscal tear. This needs to be treated fairly urgently (within days, not weeks), and it needs a knee arthroscopy ASAP! …. If a locked, displaced bucket-handle meniscal tear is just left and the knee remains locked, then the torn meniscal fragment will become shredded and it will scar up and contract – it may then be impossible to reduce the displaced meniscal tissue back into place and repair the tear … in which case the torn fragment will simply need to be excised (removed). Most bucket-handle meniscal tears are large tears, and if they need to be trimmed then this often ends up entailing removing pretty much the entirety of the whole meniscus. The more meniscal tissue is lost, the less of a shock absorber there is in the knee, therefore the more wear and tear there will be and the greater the likelihood of the knee subsequently developing arthritis.

Leaving a locked knee for any length of time (particularly in a younger person) is, quite simply, a sin.

In older patients, sometimes the full extension in the knee joint is slowly and gradually lost, rather than it being a sudden or intermittent thing. This gradual progressive inability to fully straighten out the knee is not called ‘locking’, but instead this is referred to as a ‘fixed flexion deformity’, and it is a typical sign of degeneration/arthritis developing in the joint. It tends to be due to a combination of bony spurs developing in the knee (osteophytes) plus thickening and tightening of the lining of the knee (the capsule) plus tightening-up of the ligaments and tendons around the joint. Degenerative fixed flexion deformity of the knee is something that can only be cured or reversed by knee replacement surgery (if/when the patient’s symptoms actually become bad enough to justify it).


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If a joint swells up, then this is highly significant, although often not very specific. It is a sign that there is something wrong inside the joint, but if frequently does not actually tell you what.

If a knee swells up generally after any kind of accident or injury then this implies strongly that something significant is damaged in the joint -

  • If a knee swells up a lot after an injury, and the swelling is large, then this suggests that there is a haemarthrosis (bleeding) in the joint. The most common cause of this is a ACL rupture.
  • If a knee swells up after an injury but the swelling is not particularly large and the swelling doesn’t appear rapidly, but develops a while later (like that evening or the following day) then this implies that there is an effusion in the joint, which means that there is increased joint fluid (i.e. ‘water on the knee’). This is more in keeping with a meniscal cartilage tear.
  • If a knee intermittently swells up during/after any kind of activity/exercise, then this implies that there could be a meniscal tear or some specific focal articular cartilage damage, or potentially more widespread articular cartilage wear and tear (degeneration/arthritis).
  • If a knee swells up without any particular specific trauma then this suggests that there is likely to be inflammation in the joint (e.g. rheumatoid arthritis or gout) or potentially an infection.
  • Infection within just the skin is called cellulitis. This can be extremely painful and normally requires high-does antibiotics (sometimes intravenously). However, infection inside a joint is called a ‘septic arthritis’. This causes very severe pain, with marked heat in the joint, redness and swelling. This is an orthopaedic emergency. It is not sufficient just to give antibiotics for a septic arthritis – the pus and infection in the joint need to be washed out thoroughly via keyhole surgery (an arthroscopy), with samples being taken to see what potential bugs (bacteria) might actually be causing the infection, and the patient will then need high-dose intravenous antibiotics. If a septic arthritis is just left, then the infection will destroy the articular cartilage on the joint surfaces and this will lead to severe damage and premature arthritis in the joint.


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