Common Causes of Knee Pain in Younger People

Knee pain in young adults can stem from a range of physical and biomechanical factors. While injuries do occur, many young Australians experience discomfort without a clear triggering event. Here are the most common causes:

Patellofemoral pain syndrome (PFPS)

Often called “runner’s knee”, patellofemoral pain syndrome in young adults involves pain around or behind the kneecap. It’s common among young adults who engage in activities involving running, jumping, or squatting. Poor tracking of the patella due to muscular imbalances or biomechanical issues can cause irritation and inflammation.

Even small alignment issues in the hips or ankles can affect how the patella moves, placing extra pressure on the joint surfaces. Left unmanaged, this condition can become chronic and may limit participation in sport or daily tasks like stairs or prolonged sitting.

Ligament sprains and strains

ACL, MCL, or other ligament injuries aren’t limited to professional athletes. A quick pivot in netball or an awkward landing in basketball can overstretch these key stabilisers. Even minor sprains can cause ongoing discomfort if not properly managed.

Partial ligament injuries, though less dramatic than full tears, can result in subtle instability and compensation patterns that affect the entire lower limb. Early rehab is essential to restore normal movement and reduce the risk of reinjury or long-term instability.

Osgood-Schlatter disease

Typically seen in active teens aged 10 to 15, this condition causes pain and swelling just below the kneecap due to inflammation at the growth plate of the shinbone. It often resolves with time, but symptoms can persist into early adulthood if not properly addressed.

Activities that involve repetitive jumping, sprinting, or kneeling often aggravate symptoms. Managing load, modifying sport, and focusing on quad flexibility and strength can help young athletes stay active while symptoms settle.

Overuse injuries from sports or the gym

High-frequency training with limited recovery, especially during strength training, long-distance running, or HIIT, can lead to tendonitis or bursitis. These conditions develop when repetitive strain outpaces the body’s ability to heal, causing pain and stiffness around the knee joint.

In younger adults, these overuse conditions often reflect a mismatch between load and tissue capacity. A sudden increase in training volume, poor technique, or neglecting rest days can be contributing factors. Identifying these early allows targeted management without needing to stop training altogether.

Growth-related changes during adolescence

Rapid growth spurts can temporarily affect muscle flexibility and joint mechanics, leading to awkward movement patterns and knee discomfort. This is particularly common in late high school or early uni years.

As bones lengthen faster than muscles adapt, temporary imbalances may cause tension in the knees, especially during sports. These changes are usually self-limiting, but supportive physio and strength work during this phase can reduce pain and help young people move more confidently.

Hip and ankle mobility issues

A restricted range in the hips or ankles often shifts excessive force to the knees during movement, which over time may contribute to pain or instability. This biomechanical chain reaction is often missed unless assessed by a health professional.

In young adults, limited ankle dorsiflexion or hip control may not cause pain directly, but it can alter squat depth, running mechanics, or landing form, quietly overloading the knees. Addressing these upstream areas is often key to long-term resolution.

How Lifestyle Affects Young Knees

Knee pain isn’t just about what happens on the sports field. Your day-to-day habits and routines can have a significant impact.

Sedentary lifestyle meets sudden activity

Many young adults spend hours seated, whether at uni, work, or gaming, and then jump straight into intense sport or gym sessions. This mismatch between passive and high-load activity can lead to stiff joints, weakened muscles, and a higher risk of injury.

Muscles around the hips and knees can tighten from prolonged sitting, reducing joint mobility and shock absorption. When activity resumes, the knees often compensate for this tightness, increasing the likelihood of strain or overload.

Poor movement patterns and posture

Sitting with rounded shoulders or collapsed knees, walking with flat arches, or squatting with poor alignment can all contribute to long-term knee stress. These habits are often subtle but can create cumulative strain over time.

Postural patterns developed in adolescence may persist into early adulthood, especially with minimal movement variety. Addressing these through movement retraining or physio can improve performance and reduce injury risk.

Inadequate recovery or sleep

Lack of rest or sleep can delay tissue repair and increase inflammation. This makes even minor strains feel worse and slow to heal, especially when physical activity remains high.

Recovery isn’t just about rest days. Nutrition, hydration, stress levels, and sleep quality all contribute to how well tissues repair after training. Supporting these factors creates a better environment for healing and adaptation.

Footwear and surface choices

Inappropriate shoes (e.g. worn-out runners or unsupportive casual sneakers) can alter lower limb alignment. Hard surfaces like concrete courts or improper gym flooring may also increase joint loading.

Shoes that lack cushioning or arch support can subtly shift pressure into the knees, especially during repetitive activities. Replacing worn-out footwear and choosing sport-specific shoes can reduce cumulative stress.

Symptoms to Watch For

Not all knee discomfort is cause for concern, but there are key signs that may suggest an underlying issue worth checking:

• Clicking or popping that occurs repeatedly or is accompanied by pain
• Sharp or stabbing pain during activity, especially when bending or twisting
• Pain after prolonged sitting, squatting, or going down stairs is often linked to patellofemoral pain
  
• Swelling or warmth around the joint, which may indicate inflammation
• The knee giving way or feeling unstable during daily movements
• Persistent stiffness or tightness, particularly in the morning or after rest
• Localised tenderness when touching or pressing specific areas (like the kneecap or tendon below it)

Other subtle symptoms like a dull ache that worsens with load, or a feeling of heaviness or “pressure” around the knee, can also signal early tissue stress. Some signs—particularly when they persist or begin to affect daily activity—may resemble the early symptoms of knee arthritis. Recognising these early may help distinguish between temporary overload and more progressive concerns. Don’t ignore recurring patterns, early care can prevent escalation.

Assessment and Diagnosis

If knee pain lingers for more than a few days or interferes with your normal activities, early assessment is important. A qualified knee surgeon in Sydney can help identify the cause and create a management plan that suits your goals and lifestyle.

Role of the GP and physiotherapist

Your GP can assess your symptoms, rule out systemic issues (like infections or inflammatory conditions), and refer you to a physiotherapist or knee specialist if needed. Physiotherapists play a key role in biomechanical assessment and developing strength and mobility programs tailored to your needs.

They may assess muscle imbalances, joint control, and how your body moves during tasks like squatting or walking. Early physiotherapy for knee pain can support a safe return to activity and reduce the chance of recurring issues.

When imaging may be appropriate

In many cases, knee pain can be diagnosed without scans. However, imaging such as X-rays or MRI may be recommended if:

• Pain is severe or long-standing
• There is suspicion of structural damage (e.g. torn ligament or cartilage injury)
• There is unexplained swelling, instability, or loss of range of motion

Unnecessary imaging can delay care, so your health provider will usually start with a clinical examination. When imaging is used appropriately, it can guide treatment decisions or help rule out less common conditions.

Prevention and Early Management

The good news? Many causes of knee pain in young adults are preventable or manageable with proactive care.

Strength training and gradual load

Building muscle strength, particularly in the glutes, quads, and calves, can help offload pressure from the knee joint. Focus on balanced programs that include core stability and progressive loading rather than quick jumps in intensity.

Progressive overload allows tendons and cartilage to adapt safely. Including unilateral (single-leg) exercises can help identify and correct asymmetries that may increase risk.

Warm-up and movement preparation

Warming up before sport or exercise prepares your muscles and joints for activity. This can reduce the risk of strain or sprain. Include dynamic stretches and low-impact drills that activate key movement patterns.

A proper warm-up also improves coordination and mental readiness, especially valuable for reducing non-contact injuries like sudden ACL sprains during sport.

Good footwear and surface awareness

Choose shoes with proper support for your activity, whether you're running, lifting weights, or playing court sports. Be mindful of high-impact surfaces and avoid repetitive jumping or sprinting on hard ground without rest days.

Rotating footwear and adjusting training loads based on surface type (e.g. switching from concrete to grass) can reduce repetitive joint loading.

Cross-training and rest

Mixing up your physical activity, like alternating between running, cycling, or swimming, can reduce repetitive strain. Schedule rest or active recovery days to allow tissues to heal and adapt.

Recovery doesn’t mean stopping movement. Low-load activity like walking or mobility work can promote circulation and speed up tissue repair between higher-intensity sessions.

Correct technique and form

Whether it’s squatting at the gym or playing footy on the weekend, technique matters. Poor form can overload the knee, especially when fatigue sets in. Seek guidance from a coach, trainer, or physio if unsure.

Filming your movements or using mirrors can help identify subtle form errors that might otherwise go unnoticed. A few small adjustments can often reduce pain and improve performance.

When to Escalate Care

Early intervention can make a significant difference. But how do you know when to seek further help?

Red flags that warrant professional attention

• Pain that worsens despite rest or rehab
• Swelling that returns or increases after activity
• Locking or catching of the joint
• A visible deformity after injury
• Instability that makes you hesitant to move or exercise
• Any trauma with a popping sound followed by immediate swelling or difficulty walking

These may suggest ligament tears, meniscal damage, or other internal injuries that require a tailored management plan.

Delaying care after these signs can prolong recovery or increase the risk of secondary problems like muscle weakness or altered gait. Seeing your orthopaedic knee surgeon or physio promptly helps ensure the right steps are taken at the right time.

Protecting Young Knees for the Long Term

Knee pain in young adults is more common than you might think, but it doesn’t have to be something you just “put up with”. Whether you’re a weekend warrior, gym enthusiast, or navigating a high-load uni schedule, your knees do a lot of work for you.

Understanding the causes, recognising early warning signs, and acting early can prevent minor issues from becoming major ones. Prioritise strength, movement quality, recovery, and don’t hesitate to seek support from a knee specialist if something doesn’t feel right.

Building lifelong movement habits now, before injury becomes chronic, is one of the best investments you can make in your future mobility and independence.

Disclaimer: This content is intended for informational purposes and does not replace professional medical advice, diagnosis, or treatment. Always consult a registered health practitioner before beginning any treatment or making decisions about your healthcare. You can verify registration at AHPRA’s public register. Individual outcomes may vary depending on personal health circumstances and the nature of the injury.