Causes of knee pain and why the exact source matters
One of the more challenging things about knee pain is that the place you feel the pain does not always tell us exactly what is causing it.
Several structures sit close together around the knee, and different conditions can initially feel very similar. Pain at the front of the knee, for example, may come from the patellofemoral joint, a tendon, the fat pad, a bursa or another nearby structure.
The same applies around the outside of the knee, where pain from the iliotibial band can occur close to symptoms associated with a tendon or ligament.
That is why understanding the causes of knee pain is not simply about identifying where it hurts. We also need to consider how the symptoms started, the type of load involved, how the knee behaves during movement and what other signs are present.
The knee is more complex than a simple hinge
The knee is often thought of as one joint that bends and straightens, but it is actually made up of three separate joints.
The tibiofemoral joint is the main weight-bearing joint where the thigh bone, or femur, meets the shin bone, or tibia.
The patellofemoral joint is where the kneecap, or patella, glides over the front of the femur as the knee bends and straightens.
There is also the smaller superior tibiofibular joint on the outside of the knee, where the tibia meets the fibula.
Because the knee is designed more for mobility than intrinsic bony stability, it relies heavily on surrounding muscles, tendons, ligaments and cartilage to control movement and manage force.
This allows us to run, jump, pivot and change direction, but it also means there are many potential sources of pain.
Knee pain can begin suddenly or build over time
Broadly, knee pain tends to develop in three ways.
It may follow an acute injury, develop gradually through repeated load or biomechanical factors, or be associated with degenerative changes such as osteoarthritis.
The way the pain started can provide important clues.
A knee that becomes swollen after twisting during football has a very different history from a knee that gradually becomes painful after several weeks of increased running or repeated kneeling at work.
There may not always be one dramatic moment when something “goes wrong”.
In gradual-onset knee pain, the tissues may simply have been exposed to more load, repetition or intensity than they currently have the capacity to manage.
Acute traumatic knee injuries
Sudden knee injuries can happen when the joint is twisted, compressed, struck directly or rotated while carrying load.
Ligaments are one possible source.
The anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) sit deeper within the knee, while the medial collateral ligament (MCL) and lateral collateral ligament (LCL) help support the inner and outer sides.
The meniscus can also be injured. The menisci are crescent-shaped cartilage structures that sit between the femur and tibia and help distribute load across the joint.
Other acute injuries may involve patellar dislocation or instability, the infrapatellar fat pad beneath the kneecap tendon, or tendon injuries around the knee.
Some high-force injuries can also involve fractures or more serious structural damage requiring further medical investigation.
The mechanism of injury becomes particularly important here. Knowing the direction of force, whether the knee twisted or collapsed, when swelling appeared and if the knee now locks or gives way can help narrow down what may have been affected.
Why pain at the front of the knee can be difficult to interpret
Anterior knee pain is a good example of why the location of pain does not always identify the exact problem.
Patellofemoral pain is one possibility, but symptoms in a similar area may also come from the patellar tendon, quadriceps tendon, infrapatellar fat pad, surrounding bursae or structures involved in kneecap stability.
In practice, I see how easily these presentations can overlap. Patellar tendinopathy can feel very similar to fat pad irritation, while peri-patellar bursitis can sometimes behave more like a deeper joint problem because the structures sit so close together.
That is why I do not rely on the pain location alone. How the symptoms behave under load, the precise area of tenderness, movement patterns and the history behind the problem all help distinguish what may be involved.
The difference matters because these conditions do not necessarily respond to the same rehabilitation approach
Pain on the outside of the knee has several possible causes too
The outer side of the knee is another area where symptoms can overlap.
Iliotibial band friction syndrome is commonly associated with running and other repetitive lower limb activity.
But pain in this area may also involve the biceps femoris tendon, which attaches around the outer back of the knee, or the lateral collateral ligament.
Again, the structures are close together but the underlying problem is not necessarily the same.
A lateral collateral ligament injury following a specific traumatic event should not automatically be managed in the same way as a gradual-onset iliotibial band problem.
The history, movement pattern and behaviour of the symptoms help separate these possibilities.
Knee pain can also be related to joint irritation and degeneration
Not all knee pain is associated with an acute injury or tendon problem.
Synovitis, which is inflammation of the joint lining, can cause a more generalised ache, warmth and swelling within the knee.
Osteoarthritis is another common cause of knee pain.
Degenerative changes can affect the tibiofemoral joint, the patellofemoral joint or both. People may experience aching, stiffness, reduced mobility and difficulty with activities such as walking, stairs or rising from a chair.
The presence of osteoarthritis does not automatically mean surgery is required.
For some people, conservative management focuses on strength, movement and increasing the knee’s capacity for everyday activity. Our approach draws on principles used within the GLA:D rehabilitation framework while adapting exercise and loading to the person in front of us.
Knee pain in growing children can have different causes
Children and adolescents can experience knee pain for reasons that are less common in adults.
Osgood-Schlatter disease affects the attachment area below the kneecap and is commonly seen during periods of growth.
Sinding-Larsen-Johansson syndrome affects the lower pole of the patella and can also occur in active growing children.
These conditions are related to stress around developing attachment sites and often require sensible activity and load management rather than simply stopping all movement.
It is also worth remembering that in younger people, pain felt at the knee can occasionally originate from the hip.
This is another reason assessment needs to look beyond the painful area when the presentation does not fit neatly with a local knee problem.
Sometimes the knee is the victim rather than the whole problem
For more biomechanical presentations, the knee may only be one part of the picture.
The hip, ankle and foot all influence how force travels through the lower limb.
If there is reduced strength, altered muscle length, joint stiffness or poor movement control elsewhere in the chain, the knee may be exposed to greater load during certain activities.
That does not mean every person with knee pain has a hip or foot problem.
It means we need to assess how the lower limb works as a whole rather than assuming the painful structure exists in isolation.
This is particularly relevant for gradual-onset problems where there has been no clear injury event.
Load matters just as much as structure
One of the most useful questions in knee assessment is often:
What changed before the pain started?
A sudden increase in running distance, repeated downhill work, more frequent training, extra kneeling, a return to sport or a change in footwear can all alter the amount of stress placed through the knee.
The tissue itself may be healthy, but the load placed on it may have increased faster than its capacity to adapt.
This is why load history matters.
For biomechanical knee problems, we look at both intrinsic factors, such as strength, muscle length and movement control, and extrinsic factors, such as training volume, surfaces, footwear and repetition.
Why clicking, locking and giving way are useful clues
People often become concerned when their knee clicks or makes noise.
A click on its own does not necessarily identify a specific problem, but symptoms such as clicking, locking or giving way can provide valuable information when considered together with the rest of the history.
True locking may suggest that something is mechanically restricting the joint.
Giving way may indicate instability, weakness or another issue affecting the way the knee is being controlled.
Swelling is another useful clue.
The amount of swelling, when it appeared and whether it seems to be inside or outside the joint capsule can help build a clearer picture of the structures involved.
No single sign gives us the full answer, but together they can make the clinical picture much more specific.
Why an accurate assessment matters
From my own experience treating knee pain, I find that the more specific we can be about the structure causing the symptoms, the more useful the rehabilitation plan becomes.
Many tissues around the knee can become irritated or overloaded, and several can present in very similar ways.
Patellar tendinopathy and fat pad impingement are one example. Pain from the lateral collateral ligament can sit close to symptoms from the iliotibial band, even though the two problems may need quite different management.
A thorough history gives us some of the most important clues.
I want to know if there was a clear mechanism of injury or if the pain came on gradually. Was there an increase in load or repetition beforehand? Has the knee been clicking, locking or giving way? If there was trauma, what was the direction of force? Where is the swelling, and does it appear to be inside or outside the joint capsule?
Detailed palpation and movement testing then help refine that picture further.
The diagnosis may become more obvious over time, but identifying the likely problem as early as possible can make rehabilitation more focused from the beginning.
How physiotherapy approaches different causes of knee pain
Once the likely source of the pain is better understood, treatment can be matched more closely to the presentation.
For an acute injury, early priorities may include settling inflammation, restoring knee movement and returning to basic functions such as normal walking.
For more biomechanical problems, we may look beyond the knee itself and assess the whole kinetic chain through the hip, knee, ankle and foot.
In practice, I try to work out which factors are having the greatest influence rather than treating every possible contributor equally.
That may involve strength or muscle-length issues, joint restrictions, movement control or changes in training and activity load.
Treatment can include manual therapy, Mulligan Mobilisation with Movement, taping and progressive exercise rehabilitation where appropriate.
The longer-term goal is to rebuild enough capacity for the demands the person actually needs to manage, from stairs, squatting and kneeling through to running, jumping, landing and change of direction.
The cause of knee pain shapes the rehabilitation
There is no single rehabilitation program that suits every painful knee.
A ligament injury, patellar tendinopathy, patellofemoral pain and osteoarthritis may all involve exercise and strengthening, but the loading, timing and progression can be quite different.
One thing I have learned in practice is that the structure that hurts and the factors driving the problem are not always exactly the same thing.
The knee may be the painful area, while strength, movement, training load or mechanics elsewhere in the lower limb are also contributing.
That is why rehabilitation needs to address both the tissue that is irritated and the demands the person needs to return to.
If further investigation is required, imaging or referral to a sports physician, orthopaedic specialist or podiatrist may also be appropriate.
People recovering after surgery can find more information about post operative physiotherapy, while those managing a sporting injury can read about physio for sports injuries.
These four swaps should give the knee blog noticeably more of Anthony’s practitioner voice without changing its overall style or adding much length.
Physiotherapy for knee pain in Aldinga
If knee pain is affecting walking, stairs, work, exercise or sport, Aldinga Bay Physio provides assessment and rehabilitation across Aldinga and surrounding southern areas.
We look at how the symptoms developed, which knee structures may be involved and whether factors elsewhere in the lower limb are contributing to the problem.
You can learn more about our physio for knee pain in Aldinga or book an appointment for an assessment.
You can also find information about physio for back pain, physio for neck pain and physio for shoulder pain.