Patellofemoral Joint Osteoarthritis: Causes, Symptoms, and Treatment

Patellofemoral osteoarthritis is a degenerative disease of the joint between the patella and the femur. Simply put, it doesn't affect the entire knee, but rather its anterior region, which is particularly stressed when squatting, going up and down stairs, rising from a chair, and sitting for long periods with bent knees. This is why this form of the disease often causes very characteristic anterior pain, yet often remains underdiagnosed. [1]

The patellofemoral compartment is one of the most commonly affected knee joint compartments in osteoarthritis. A systematic review found that the crude prevalence of patellofemoral osteoarthritis was approximately 25% in population-based cohorts and approximately 39% in symptomatic cohorts. Another meta-analysis found that approximately half of people with knee pain or radiographic osteoarthritis have patellofemoral involvement. [2]

The clinical significance of this form of osteoarthritis is that it can be isolated or combined with tibiofemoral involvement. The isolated form most often presents with pain in the anterior knee and difficulty with activities that involve prolonged knee flexion or load-bearing. The combined form is usually more severe because the anterior pain is accompanied by more typical symptoms of general knee osteoarthritis. [3]

A separate problem is that patellofemoral osteoarthritis is often disguised as "regular knee pain," "sports-related," or "chondromalacia." In the early stages, a person often hears advice to simply reduce the load on the leg, although it would be more appropriate to understand at this point whether there are anatomical prerequisites for abnormal patellar glide, consequences of instability, or already-developed structural changes in the cartilage and subchondral bone. [4]

The modern view of this disease has become much more precise. It is now considered not as a uniform "knee wear and tear," but as a distinct clinical phenotype with its own biomechanical causes, typical symptoms, and treatment strategies. Therefore, general reviews of knee osteoarthritis should be applied to this condition with caution. [5]

Table 1. What usually indicates the patellofemoral variant

Sign	Why is this important?
Pain in the front of the knee	typical localization for the anterior section
Increased pain when going down stairs	the patellofemoral joint is heavily loaded in flexion
Pain after sitting for a long time	characteristic of prolonged knee flexion
Cracking and pain when squatting	often reflect contact loads on the patella
Pain when getting up from a chair	another typical anterior trigger
Associated with patellar instability in the past	increases the likelihood of this particular form of the disease

Sources for the table: [6]

Who gets sick more often and why does the disease develop?

Age remains a major risk factor, but it's not a disease restricted to the very elderly. Patellofemoral osteoarthritis also occurs in middle-aged individuals, especially those with a history of injuries, patellar dislocations, knee surgery, or long-term athletic overuse. A review of the prevalence of isolated patellofemoral osteoarthritis in individuals over 55 years of age found estimates of approximately 24% in women and approximately 11% in men, highlighting the significant frequency of this condition. [7]

The most consistently identified risk factors include female gender, excess body weight, age, heavy physical work, and anatomical features of the patellofemoral joint. A 2024 study specifically identified older age, female gender, obesity, manual labor, and abnormal patellofemoral parameters as predictors. This is consistent with the biomechanical logic of the disease: the greater the pressure on the anterior knee and the less centered the patella, the higher the risk of cartilage damage. [8]

Particularly important factors affecting patellar gliding include patellar elevation, femoral trochlear dysplasia, lateralization of the patellar tendon, and the consequences of instability and previous dislocations. These conditions do not always immediately cause osteoarthritis, but they create conditions in which the load is distributed unevenly and part of the articular surface wears out more quickly. [9]

Obesity also plays a significant role. It increases not only mechanical stress but also the metabolic inflammatory effects on joint tissue. Some studies have shown that obese individuals experience greater deformation and stress of the patellofemoral cartilage after functional loading than individuals with normal body weight, making disease progression more likely. [10]

The pathogenesis of the disease consists of several factors: chronic overload, microtrauma to the cartilage, remodeling of the subchondral bone, bone marrow changes, synovial inflammation, and muscle dysfunction. When the patella does not move along an optimal trajectory, part of the load is concentrated in a limited area, and over time, this leads to localized cartilage thinning, osteophytes, and pain. Therefore, treatment must consider not only the cartilage itself but also the mechanics of the entire limb, including the pelvis, femur, lower leg, and foot. [11]

Table 2. Main risk factors

Factor	How is it related to the disease?
Age	the frequency of structural changes increases
Female gender	the disease is more common
Obesity	increases mechanical and metabolic load
Heavy physical labor	increases chronic knee overload
High patella	worsens load distribution
Femoral trochlear dysplasia	contributes to improper sliding
History of dislocations and instability	damage cartilage and change biomechanics
Previous knee injury	increases the risk of early degenerative processes

Sources for the table: [12]

How the disease manifests itself and why it is dangerous to underestimate it

The most common complaint is anterior knee pain, that is, pain "behind" or around the patella. It often intensifies when going up and down stairs, rising from a sitting position, squatting, rising from a squatting position, or sitting for long periods in a car or movie theater. For the patient, this presents as a very mundane yet persistent problem: the knee may be tolerable on a flat surface, but sharply manifests itself during any flexed movement. [13]

Another common symptom is a crunching, clicking, and friction sensation in the anterior knee. Painless crunching alone does not necessarily indicate osteoarthritis, but if it is accompanied by pain, stiffness, and limitation of daily activity, it can no longer be considered a harmless finding. In the early stages, it is especially common for the pain to be intermittent but to occur regularly during the same mechanical situations. [14]

Some patients experience episodes of swelling, a feeling of instability, decreased tolerance for walking up stairs, and a feeling that the knee "doesn't like" prolonged sitting. Magnetic resonance imaging studies show that bone marrow changes, osteophytes, and cartilage damage in the patellofemoral region are associated not only with pain but also with decreased daily activity and poorer functional outcomes. [15]

If the disease is left untreated for a long time, not only the joint itself suffers, but also the person's behavior. They begin to avoid stairs, squats, long walks, public transportation, exercise, and even ordinary household activities. This leads to decreased quadriceps strength, impaired motor control, and further increased mechanical vulnerability of the knee. Thus, a vicious cycle develops: pain leads to sparing, sparing leads to weakness, and weakness intensifies the pain. [16]

In later stages, a combination of severe pain, noticeable limitation of function, and the development of tibiofemoral osteoarthritis may occur. In this case, the clinical picture is no longer localized, and the patient finds it more difficult to walk, stand, tolerate normal everyday activities, and maintain normal motor activity. This is why early control of symptoms and movement mechanics is more important than it seems in the early stages of the disease. [17]

Table 3. Typical symptoms and signs of trouble

Symptom	What could it mean?
Anterior knee pain	the most typical complaint
Pain when going down stairs	characteristic overload of the anterior section
Pain after sitting for a long time	joint irritation in flexion
Painful crunching sound	degenerative changes in the surface are possible
Swelling after exercise	reactive inflammation and congestion
Worse when squatting and standing up	high contact load on the joint
Increasing limitation of a function	risk of progression and involvement of other departments

Sources for the table: [18]

How is the diagnosis confirmed and what is important not to miss?

Diagnosis begins with a conversation and examination. It's important for the doctor to determine the exact location of the pain, what movements trigger it, whether there have been any previous patellar dislocations, sports injuries, surgeries, episodes of instability, weight gain, and how long the symptoms have been interfering with daily life. Even at this stage, it's possible to suspect that the source of the pain is located in the patellofemoral region. [19]

During examination, the limb axis, patellar position, tenderness along the patellar margins, crepitus, range of motion, presence of effusion, hip muscle strength, and pelvic and hip control during functional testing are assessed. Not only local signs but also the entire kinematic chain are important, as gluteal muscle weakness, excessive hip adduction, or impaired foot control can increase patellofemoral strain. [20]

The basic imaging modality remains a knee joint radiograph with the knee supported, and for the anterior region, the axial patellar projection, often referred to as the skyline or Merchant projection, is particularly useful. Classic studies have shown that this projection is more reproducible and accurate for assessing patellofemoral joint space narrowing and localizing changes than a lateral radiograph alone. [21]

Magnetic resonance imaging (MRI) is not necessary for everyone, but it is particularly useful when symptoms are severe and radiography is still uninformative, when it is necessary to evaluate cartilage, bone marrow changes, the condition of the subchondral bone, and associated intra-articular problems. MRI reveals changes that are not visible on conventional radiography, including cartilage damage and bone marrow lesions, and is therefore especially valuable in early or questionable cases. [22]

Differential diagnosis includes patellofemoral pain without osteoarthritis, meniscal injury, inflammatory knee disease, osteonecrosis, intra-articular loose bodies, tendon pathology, and generalized knee osteoarthritis. It is especially important not to overlook the consequences of patellar instability, as in such patients, anterior pain may be associated with significant anatomical abnormalities requiring a different approach.[23]

An immediate in-person evaluation is necessary if pain develops after an injury, the knee swells sharply, joint locking develops, there is significant instability, fever, severe limitation of extension, or a sudden inability to bear weight on the foot. These symptoms go beyond "ordinary osteoarthritis" and require a search for another, sometimes urgent, cause. [24]

Table 4. Practical diagnostic route

Step	What are they doing?	Why is this necessary?
1	They clarify the localization and triggers of pain	suspect the anterior knee
2	A history of trauma and instability is obtained.	understand the cause of the overload
3	Conduct inspection and functional tests	evaluate the mechanics of movement
4	An axial radiograph of the patella is taken.	confirm bone and joint changes
5	Magnetic resonance imaging is prescribed according to indications	see cartilage, bone, and early structural changes
6	Rule out other sources of pain	don't miss the meniscus, inflammation, or consequences of injury

Sources for the table: [25]

How is it treated today and what really helps?

Treatment almost always begins with a conservative program rather than surgery. The primary goal at this stage is not to "erase the arthrosis," but to reduce pain, improve function, increase muscle strength and endurance, correct triggering loads, and slow further deterioration. For knee osteoarthritis in general and the patellofemoral phenotype in particular, a non-drug approach is considered the mainstay of therapy. [26]

The first component of treatment is patient education. It's important to explain that anterior knee pain is typically aggravated not by "any movement," but by specific types of stress: deep squats, prolonged sitting, frequent climbing and descending stairs, and repeated standing from a low position. Reducing these stresses for a short period often helps relieve pain, but completely avoiding movement is not the goal of treatment. The goal is to gradually increase stress, not eliminate it. [27]

The second and most important component is therapeutic exercise. The American Academy of Orthopaedic Surgeons recommends supervised exercise programs to reduce pain and improve function in knee osteoarthritis, and for patellofemoral osteoarthritis, individual studies show the benefit of targeted programs with exercises, education, manual elements, and taping. In a 2015 randomized trial, this combined approach improved short-term assessment and reduced pain better than education alone. [28]

In practice, the emphasis is usually on strengthening the quadriceps, gluteal muscles, and the muscles that control the position of the hip and pelvis. This is important because pain relief in many patients is associated not only with localized stimulation of the knee but also with improvements in the entire biomechanical chain. The exercise program is tailored individually: some people are more suited to closed kinematic chains with shallow flexion, others to isometric work, and others to walking, cycling, or swimming. [29]

If a patient is obese or significantly overweight, weight loss becomes part of the treatment plan, not a general recommendation for the future. The American Academy of Orthopaedic Surgeons recommends sustained weight loss to improve pain and function in overweight and obese individuals. This is especially logical for the patellofemoral joint, which is very sensitive to mechanical overload. [30]

Topical nonsteroidal anti-inflammatory drugs (NSAIDs) are usually the first choice of medication, unless contraindicated. According to the American Academy of Orthopaedic Surgeons, they improve function and quality of life in knee osteoarthritis. For more severe pain, oral NSAIDs can also be used, but the risks to the stomach, kidneys, and cardiovascular system, as well as drug interactions, must be considered. [31]

Simple analgesics can be used, but according to current data, they are generally inferior in clinical effectiveness to nonsteroidal anti-inflammatory drugs. Opioid painkillers are not recommended for the treatment of knee osteoarthritis: the American Academy of Orthopaedic Surgeons notes an increase in adverse events and a lack of convincing efficacy sufficient for their routine use. Therefore, relying on strong painkillers for long-term treatment of chronic patellofemoral osteoarthritis is a poor strategy. [32]

Taping and orthoses may help some patients, but the evidence is not entirely clear. For knee osteoarthritis in general, orthotics are accepted as a means of improving pain and function, but in the patellofemoral subtype, studies have shown a mixed picture: one randomized trial found no clinically significant effect of a dedicated real orthosis, while another showed a reduction in pain and bone marrow lesions. A 2021 systematic review concluded that there is good evidence to support a combined physical therapy approach, but the long-term effects of biomechanical devices remain unclear. [33]

Injections are used as a complement to, not a substitute for, rehabilitation. Intra-articular glucocorticosteroids can provide short-term pain relief, as reflected in the recommendations of the American Academy of Orthopaedic Surgeons. However, hyaluronic acid, according to the same recommendation, should not be used routinely for symptomatic knee osteoarthritis. This is especially important for the patellofemoral subtype: injections can act as a bridge that facilitates exercise performance, but do not solve the problem of impaired mechanics on their own. [34]

Platelet-rich plasma injections remain an area of interest but are not a first-line standard. The American Academy of Orthopaedic Surgeons rates their evidence for knee osteoarthritis as limited, and a 2025 review of symptomatic isolated patellofemoral osteoarthritis reported clinically significant improvements in pain and function in the included small studies. The problem is that plasma preparation protocols, patient selection criteria, and study designs vary widely, so it is too early to establish a reliable standard. [35]

Surgery is considered when pain and functional limitation persist despite comprehensive conservative treatment, and imaging confirms localized, severe damage. In very selective indications, organ-preserving interventions, such as partial lateral facetectomy, may be considered, but the evidence base for these is significantly weaker and they are not suitable for everyone. For severe, isolated patellofemoral osteoarthritis, patellofemoral arthroplasty remains the more standard surgical option in carefully selected patients. [36]

If the lesion is truly isolated and the rest of the knee is relatively intact, patellofemoral arthroplasty can yield good functional outcomes. A 2021 meta-analysis found that in the first 2 years after surgery, patellofemoral arthroplasty was superior to total knee arthroplasty in terms of function and physical activity, with no significant differences in complications, revisions, or satisfaction. However, further progression of tibiofemoral osteoarthritis remains a major reason for subsequent conversion to total knee arthroplasty, making patient selection critical. [37]

It is important to note that arthroscopic lavage and debridement for primary knee osteoarthritis are not routinely recommended. This position applies to knee osteoarthritis in general and is useful as a guide against excessive surgical activity, when patients are offered "cleaning out the joint" instead of full rehabilitation and thoughtful selection for truly indicated surgery. [38]

Table 5. What helps most often and what should not be considered basic treatment

Method	Role in treatment
Training and load correction	mandatory basis
Individual exercise program	the main non-drug method
Weight loss in obesity	important for reducing pain and stress
Topical nonsteroidal anti-inflammatory drugs	one of the first medicinal options
Oral nonsteroidal anti-inflammatory drugs	an option for more severe pain, if there are no contraindications
Taping and orthoses	possible in some patients, but the effect is variable
Intra-articular glucocorticosteroids	short-term relief
Hyaluronic acid	not recommended for routine use
Platelet-rich plasma	promising, but not yet standard
Patellofemoral joint replacement	option for a heavy isolated process
Arthroscopic lavage and debridement	not a routine solution for primary osteoarthritis

Sources for the table: [39]

What helps slow the deterioration and what is the prognosis?

The best prevention of progression is not complete relaxation, but a sound long-term strategy. This includes weight management, regular strength and movement control exercises, reasonable limitation of provoking overloads, and early treatment of flare-ups. For the anterior knee, it is especially important to learn to dose movements with deep flexion and repeated high loads, rather than simply "stop loading the knee altogether." [40]

The prognosis depends largely on how early joint mechanics can be addressed. If the disease is detected at a stage when motor control, muscle strength, and body weight can still be improved, symptoms can often be significantly reduced without surgery. However, if the patient adapts to pain for years, becomes motionless, and seeks treatment only when significant loss of function has occurred, conservative treatment options are more limited. [41]

Not everyone's disease progresses the same way. For some, obesity plays a major role, for others, it's the effects of instability, for others, it's athletic or work-related overload, and for others, it's a combination of several factors. Therefore, it's better to formulate a prognosis not as "arthrosis will only worsen," but as "the course of the disease depends on the specific phenotype, adherence to the treatment program, and the correct timing of surgery, if necessary." [42]

Postoperative prognosis also depends on the accuracy of selection. With good selection and a truly isolated process, patellofemoral arthroplasty can provide rapid functional gain. However, if damage to other parts of the knee is underestimated, the risk of subsequent conversion is higher. This is why high-quality preoperative imaging and critical clinical selection are more important than the desire to "do a lesser operation at any cost." [43]

In practical terms, a good prognosis is more likely to be achieved by patients whose treatment is structured sequentially: first education, exercise, weight and pain management, then assessment of response, then deciding on injections, and only then discussing surgery. This stepwise approach better aligns with the current evidence base than a chaotic attempt to alternate painkillers, injections, and random exercises without a coherent plan. [44]

Table 6. What the forecast depends on

Factor	Impact on outcome
Early initiation of treatment	improves the chance of controlling symptoms without surgery
Weight loss in obesity	reduces mechanical overload
Regular exercise	improve function and reduce pain
The presence of severe instability and anatomical factors	may accelerate progression
Accurate confirmation of isolated lesion before surgery	improves surgical outcomes
Lesions of other parts of the knee	worsens the prognosis for local intervention

Sources for the table: [45]

FAQ

Is this the same as general knee osteoarthritis?
No. It's a subtype of knee osteoarthritis in which the primary site of the problem is in the anterior region between the patella and the femur. It can exist alone or in combination with other areas of the knee. [46]

Why is going down stairs especially painful?
Because when descending and performing other flexed movements, the contact load on the patellofemoral joint increases sharply, and this area is the first to experience pain. [47]

Is it possible to avoid magnetic resonance imaging?
In many cases, yes. Initially, a medical history, physical examination, and X-rays with an axial projection of the patella are usually sufficient. Magnetic resonance imaging is used when the picture is unclear, early changes are suspected, or a more precise assessment of the cartilage and subchondral bone is needed. [48]

Do exercises help if you already have osteoarthritis?
Yes. It's one of the main treatment methods. Current guidelines for knee osteoarthritis support exercise programs, and for patellofemoral osteoarthritis, there's evidence to support targeted programs with education and physical therapy components. [49]

Are hyaluronic acid injections necessary?
As a routine method, no. The American Academy of Orthopaedic Surgeons does not recommend hyaluronic acid for routine use in symptomatic knee osteoarthritis. [50]

When should surgery be considered?
When a comprehensive conservative program fails to produce acceptable results, pain and function remain poor, and examination reveals severe, isolated damage to the patellofemoral region. [51]

Which is better: patellofemoral arthroplasty or total knee arthroplasty?
In properly selected patients with a truly isolated disease, patellofemoral arthroplasty may provide a better early functional outcome. However, if there is significant damage to other parts of the knee, total knee arthroplasty may be a more logical option. [52]

Is it possible to simply endure and walk less?
This is a poor strategy. Long-term sparing leads to weakening of muscles and decreased motor control, which often exacerbates the problem. A controlled exercise program is much more beneficial. [53]

Key points from experts

Kim Bennell, PhD, is the Redmond Barry Distinguished Professor and Director of the Centre for Health, Exercise, and Sports Medicine at the University of Melbourne.
The key practical implication of her research on knee osteoarthritis is that exercise and accessible rehabilitation should be the foundation of treatment, not a "just in case" supplement. This is especially important for the patellofemoral phenotype, as mechanical modification of motion and strength often significantly alters the course of the disease more than passive interventions. [54]

Kay Crossley, a professor, physiotherapist, and researcher at La Trobe University, is a leading expert on patellofemoral pain and osteoarthritis.
Her research supports the idea that treatment should not be generalized "for any knee," but targeted specifically at the patellofemoral region. In practice, this means focusing on precise exercises, education, manual elements, and taping in selected patients, rather than a random assortment of procedures. [55]

David Felson, MD, MPH, is a rheumatologist and professor of epidemiology at Boston University.
His work emphasizes that osteoarthritis is not simply a matter of "cartilage wear and tear," but a disease in which biomechanical factors, bone marrow changes, and loading patterns are directly linked to pain and function. This is especially important for patellofemoral osteoarthritis, because the biomechanics of movement often determine both the onset and persistence of symptoms. [56]

Conclusion

Patellofemoral osteoarthritis is a common, yet often under-recognized, cause of anterior knee pain. It cannot be simply attributed to "patella wear and tear," as specific biomechanical issues often underlie the disease: overuse, abnormal patellar glide, muscle weakness, the consequences of instability, and obesity. [57]

The most rational treatment approach today is as follows: early recognition, clarification of the disease phenotype, patient education, regular exercise, weight control, thoughtful pain management, and considering surgery only when good conservative options have been exhausted or the disease has reached a stage where local endoprosthetics are justified. This approach best aligns with the current evidence base. [58]