The two main causes of knee pain: trauma and overuse
The first reason for knee pain can be a single incident like a slip or trip at home or a collision on the sports field. These are the injuries we call traumatic knee injuries.
They need urgent attention to ensure there is no serious injury like ligament rupture, fracture or dislocation.
The second type of knee pain tends to come on more gradually after a period of activity. This could include a sudden change in activity like joining a high intensity circuit class or ramping up your cycling, running or hiking activities.
Some may aggravate their knee pain after kneeling for prolonged periods whilst gardening or going up and down stairs when moving house.
These are the type of injuries we can non-traumatic or overuse knee injuries. These injuries usually result from a sudden increase in activity or gradual accumulation of activity over days to weeks.
These are the injuries where it is hard to pinpoint one specific incident or cause. Overuse injuries tend to creep up on people gradually.
Both types of knee pain require the urgent attention of a skilled physiotherapist to ensure an accurate diagnosis is made. Once the diagnosis is clear the path to recovery is much more straight forward.
Third cause of knee pain: medical conditions
Medical conditions like gout, infections, sepsis and inflammatory arthritis can also cause knee pain. They are less common causes of knee pain.
If your knee pain is associated with symptoms like fever, feeling generally unwell, a hot and swollen knee joint as well as significantly reduced knee movement, you should seek urgent medical attention.
In these circumstances further investigations like X-rays, blood tests and even joint aspiration may be indicated.
Whilst not very common, infections and septic arthritis are very serious and require immediate medical attention via your local doctor or emergency department.
Knee joint anatomy
However, once we include all of the ligaments, tendons and cartilage things get a little more complicated.
It is important to understand that ligaments have a stabilising role in the knee joint. The knee joint ligaments essentially join the thigh bone (femur) to the shin bone (tibia).
Tendons on the other hand join muscles to bones and are responsible for helping us to move our joints.
The cartilage or meniscii of the knee act like shock absorbers for the knee joint much, like shock absorbers in a car.
To simplify the anatomy of the knee joint, physiotherapists tend to break down the knee joint into two parts:
1. Hinge knee joint
The hinge knee joing is held together by the following ligaments and cartilage (or meniscii):
- Medial collateral ligament (MCL) – on the inside of knee, prevents the knee from moving too far inwards (valgus).
- Lateral collateral ligament (LCL) – on the outside of the knee, prevents the knee from moving too far outwards (varus).
- Anterior cruciate ligament (ACL) – in the middle of the knee, prevents the knee from moving too far forwards.
- Posterior cruciate ligament (PCL) – in the middle of the knee, prevents the knee from moving too far backwards.
- Medial meniscus – sits on the inside of knee, acts as a shock absorber
- Lateral meniscus – sits on the outside of the knee, acts as a shock absorber.
In simple terms
- MCL and LCL give your knee side to side stability.
- ACL and PCL give your knee front to back stability.
- Cartilage and meniscii act as shock absorbers.
2. Knee cap joint or patellofemoral joint (PFJ)
The PFJ his is the joint between the kneecap and the thigh bone (femur) at the front of the knee joint. The role of this joint is to distribute force more evenly through the knee. The structures that make up the kneecap joint include:
- Knee cap (or patella)
- Patellar tendon – joins quadricep muscle to the shin bone, helps to straighten the knee.
- Medial patella-femoral ligament (MPFL) – small but important ligament that connects the kneecap (patella) to the thigh bone (femur).
- Its role is to help to keep the kneecap centred at the front of the knee. Often injured when someone dislocates their kneecap.
- Bursa – there are 4 main bursae in the knee. These are small, fluid-filled sacs that reduced friction between tendons and bones.
- Hoffa’s fat pad – sits under the kneecap at the front of the knee. The fat pad is a layer of fatty tissue that functions to cushion and protect the front of the knee.
A skilled physiotherapist will be able to tell you not only which joint is responsible for your pain but also which structure in that joint is the likely cause of your symptoms. Without an accurate diagnosis, treatment will often miss the mark and lead to slow or no progress.
Now that you know the anatomy of the knee joint, lets delve deeper into the most common knee injuries.
Common traumatic knee injuries
Most acute knee injuries can be diagnosed by a skilled physiotherapist taking a detailed history and conducting a physical examination.
However, it is also important to know when imaging like X-rays, CT, ultrasound or MRI are indicated. At Pollinate Health we are experts in guiding patients to when they should consider further imaging due to our extensive emergency department experience.
This injury is particularly common in people who play sports that involve a lot of twisting and turning such as football, soccer, basketball and netball.
It is important to understand that ACL injuries rarely occur in isolation. Other structures commonly associated with ACL injuries include the MCL and medial meniscus.
Bone bruising is another common finding in these injuries.
Common signs and symptoms of ACL tear:
- You may hear a “pop” when the injury occurs.
- Severe pain and swelling within 24 hours.
- The knee feels unstable or “wobbly”.
- Difficulty bearing weight on the leg.
- Inability to fully extend the leg.
Posteriocruciate ligament (PCL) rupture
With PCL, the most common mechanism of injury is hyperextension of the knee.
In addition, a direct blow to the shin while the knee is in a flexed position (which commonly occurs in car accidents) is the other way people also injure their PCL.
PCL injuries in isolation generally do well with rehabilitation and rarely need surgery.
Postero-lateral corner injuries (PLC)
These injuries are much more serious and need urgent attention.
Expert assessment and a quick referral to an orthopaedic surgeon is often required in these circumstances.
Medial collateral ligament (MCL) injuries
The most common cause of an MCL injury is a direct blow to the outside of your knee, for example, when an opponent tackles you from the side. MCL tears are classified on the basis of their severity.
- Grade I – local tenderness, minimal swelling, no laxity.
- Grade II – local tenderness, localised swelling, some laxity.
- Grade III – local tenderness, localised swelling, gross laxity, knee feels unstable.
Generally, MCL injuries do not require surgery and they are treated in a hinged knee brace. This provides support and protection to the MCL for a period of 6 weeks. Early rehabilitation is crucial for a good outcome.
The front part of the meniscus is called the anterior horn and the back part is called the posterior horn.
The most common way to injure your meniscus is with a twisting motion like when quickly changing direction. The medial meniscus is more commonly injured as it is less mobile than the lateral meniscus. There are many different types of meniscal tears as outlined below
- Posterior horn/anterior horn
- Longitudinal tear
- Radial tear
- Bucket handle tear
- Degenerative tear
The more severe meniscal injuries can cause locking of the knee with severe pain and restricted knee movement.
This occurs as the torn part of the meniscus gets caught in the knee joint. Sometimes this locking can improve spontaneously or with good physiotherapy management. However, if symptoms don’t improve urgent orthopaedic assessment is recommended.
In contrast the smaller tears generally get better with physiotherapy management.
Common fractures of the knee
The bones of the knee, including the kneecap (patella) can be broken during a fall, sporting injury or car accident. The most common fractures in the knee include:
- Shin bone at the knee (tibial plateau fracture) – these are considered high energy injuries which means people are travelling at speed (Eg. bike, scooter) or falls from a height (Eg. jumping off a ladder or back of a Ute). In these injuries the person generally lands on their feet and force is transmitted to the knee leading to a fracture.
- Kneecap (patella) – usually injured when a person falls directly on their knee.
Many people get confused by the different terms used to describe a broken bone Eg. fracture, hairline fracture, stress fracture, avulsion fracture.
At Pollinate Health we are experts in fracture management and can help to guide you through the rehabilitation process. This expertise stems from a decade of working closely with orthopaedic surgeons and front-line experience in two of the busiest emergency departments in Victoria.
Kneecap (patella) dislocation
This occurs when the kneecap moves to the outside of the knee. This is usually caused by a direct blow to the knee or activities that involve twisting or jumping.
Patella dislocations can sometimes cause avulsion fractures. These are small fractures that can occur as the kneecap slides forcefully to the outside of the knee.
Common signs and symptoms of a kneecap dislocation:
- Patient reports feeling like something “moving” or “popping out” at front of knee.
- Swelling usually develops immediately.
- The kneecap usually pops back into place on its own when the knee is straightened.
- Tender over inside border of the kneecap.
- Tensing quadriceps muscle provokes the patient’s pain.
Common overuse knee injuries
Kneecap pain (also known as anterior knee pain or patella-femoral pain)
Pain at the front of the knee is one of the most common reasons people visit their GP or physiotherapist.
Unlike traumatic injuries, anterior knee pain is usually caused by overuse. Examples include increasing your walking, running or cycling volume too quickly. Pain is usually aggravated by going up and down stairs or activities like running and cycling. Sometimes pain is also aggravated by sitting for long periods, commonly called “movie-goers knee”.
Patella tendinopathy (jumper’s knee)
Like most tendon injuries a detailed history and physical examination is required, alongside load management strategies. A graded strength and plyometric rehabilitation program are the cornerstone of improving patella tendinopathy pain and preventing it from coming back.
Fat pad impingement
The fat pad is one of the most sensitive structures in the knee so this condition can be very painful and disabling and difficult to treat. Early physiotherapy assessment and treatment are crucial to achieve an optimal outcome.
Knee bursitis, formerly known as housemaid’s knee (!!!!)
Bursae are located between bone and tendons and their role is to reduce friction. Sometimes these bursae become inflamed by a direct blow to the knee or after prolonged kneeling hence the term “housemaid’s knee”.
The symptoms of arthritis include pain, swelling and stiffness.
Osteoarthritis can be managed with physiotherapy and exercise. The most common risk factors for developing knee osteoarthritis include:
- Being overweight.
- Having a sedentary lifestyle.
- Having weak muscles.
- Genetic factors
A Baker’s cyst is a fluid-filled sac that sits behind the knee. It is usually caused by osteoarthritis.
The main symptoms include pain and swelling at the back of the knee. Sometimes you may also feel a lump at the back of the knee.
In some cases, the Baker’s cyst can rupture, causing increased pain and swelling at the back of the knee that radiates into the calf.
Whilst painful, this condition is not dangerous and will often go away on its own.
The main thing to consider is that a deep vein thrombosis (DVT) or blood clot of the vein behind your knee can feel similar to a Baker’s cyst.
Always seek medical attention if you are unsure and have risk actors for DVT.
Knee pain related to medical conditions
This is an autoimmune condition that can affect almost any joint in the body. Unlike the wear and tear nature of osteoarthritis, rheumatoid arthritis affects the lining of the joints, leading to painful swelling.
Left untreated joints develop bone erosions and eventually deformity of the joints.
Common signs and symptoms include:
- Episodic flare-up of joint pain.
- Tender, warm, swollen joints.
- Morning stiffness.
- Symptoms improve with exercise.
Pollinate Health's tips for healthy knees
- Maintain a healthy weight.
- Strengthen your leg muscles once or twice per week.
- Mix up your exercise routine so that your joints experience variety.
- Be cautious when increasing you exercise workload, err on the side of caution.
- See a health professional ASAP when things start to hurt.
It is important to discuss any usual symptoms with your family doctor. Urgent referral to a rheumatologist is also important.
There are many options for treatment of rheumatoid arthritis that will help to preserve the joint and slow down progression of this condition. Blood tests are an important part of establishing a correct diagnosis in inflammatory diseases.
In summary, look after your knees as they are the foundation of most of your activities. Seek urgent attention if pain starts to develop and stops you doing the activities you love.
Pollinate Health are experts in getting you back to enjoying movement without pain. We also understand when you need more investigations and specialist referral. Don’t hesitate to reach out for advice