Patellofemoral Arthritis (Kneecap Arthritis)
Patellofemoral arthritis is cartilage loss behind the kneecap, causing anterior knee pain that worsens when climbing stairs, rising from a chair, or walking downhill. Mr Shakir Hussain, Consultant Orthopaedic Surgeon at the Royal Orthopaedic Hospital Birmingham, treats patellofemoral arthritis with targeted surgical and non-surgical options.
What is the patellofemoral joint?
Patellofemoral osteoarthritis is the loss of cartilage between the patella (kneecap) and the trochlear groove on the front of the femur. It causes anterior knee pain that is characteristic in its pattern: worst on stairs, slopes, and after prolonged sitting, but typically less painful on flat ground. It is distinct from the more common medial compartment arthritis, though the two frequently co-exist.
The knee contains three compartments: the medial (inner), lateral (outer), and patellofemoral (between the kneecap and thigh bone). In a healthy knee, the kneecap glides smoothly in the trochlear groove of the femur as the knee bends and straightens. Smooth articular cartilage on both surfaces allows this movement without pain.
In patellofemoral arthritis, this cartilage thins and roughens. The kneecap may also track abnormally within the groove (maltracking), increasing localised cartilage stress and accelerating wear. The compressive forces on the patellofemoral joint are highest when the knee is bent, which is why stair climbing, hill walking, and rising from a chair are the activities most commonly affected.
Patellofemoral arthritis is found in approximately 10 per cent of patients presenting with knee arthritis. In many older patients, it exists alongside medial compartment arthritis, making total knee replacement the most appropriate surgical treatment. True isolated patellofemoral arthritis, where the medial and lateral cartilage remains intact, is a less common presentation.
What does patellofemoral arthritis feel like?
Pain behind or around the kneecap, worst on stairs (particularly going down), rising from a seat, and walking downhill. After prolonged sitting, the anterior knee aches and eases when the patient stands and straightens the leg: this is the cinema sign, a hallmark of patellofemoral arthritis. A grinding or creaking sensation under the kneecap during movement is common.
The distribution of patellofemoral arthritis pain is anterior (in front of and behind the kneecap), distinguishing it from the medial (inner-side) pain of typical knee osteoarthritis. However, the two patterns can co-exist, so careful examination and targeted X-ray views are needed to identify the dominant compartment.
Anterior kneecap pain
Diffuse pain behind or around the kneecap rather than the inner or outer joint line. Patients often describe pressing on the front of the knee to relieve it. The pain is reproduced by pressing the kneecap firmly against the trochlear groove (patellar grind test).
Pain on stairs and slopes
Descending stairs is typically more painful than ascending because the knee bends further and the patellofemoral compressive force is higher. Walking downhill, stepping off kerbs, and squatting reproduce the pain most reliably.
Cinema sign (prolonged sitting)
The anterior knee aches after sitting with the knee bent for 20 to 30 minutes, as in a car, cinema, or long meeting. Standing and straightening the leg provides relief. This is the cinema sign, considered pathognomonic of patellofemoral arthritis.
Grinding or creaking under the kneecap
A grating, grinding, or creaking sensation felt under the kneecap during knee flexion and extension, caused by roughened cartilage surfaces. This crepitus may be audible and is often the first symptom patients notice.
Swelling around the kneecap
Peri-patellar swelling or a mild joint effusion may develop after prolonged activity. Pronounced swelling at rest is less common in isolated patellofemoral disease than in tri-compartmental arthritis.
Quadriceps weakness
Anterior knee pain inhibits quadriceps activation, causing progressive thigh muscle wasting. Quadriceps weakness in turn reduces the dynamic support of the patellofemoral joint, creating a cycle of worsening pain and muscle loss.
What causes patellofemoral arthritis?
Patellofemoral arthritis develops when the kneecap does not track centrally in the trochlear groove, concentrating cartilage stress on a small area. Prior patellar dislocation, patellar dysplasia, repetitive high knee-load activities, and increasing age are the most important risk factors. Women are more commonly affected than men.
Key causes and risk factors include:
- Patellar maltracking. If the kneecap tracks laterally rather than centrally in the groove, cartilage on the lateral facet of the patella bears disproportionate load. This is the most common structural cause of patellofemoral arthritis.
- Prior patellar dislocation. Each dislocation episode damages the cartilage on the medial facet of the patella and the lateral trochlear groove. Recurrent dislocations substantially increase arthritis risk, particularly if the underlying trochlear dysplasia is not corrected.
- Trochlear dysplasia. An abnormally flat or convex trochlear groove fails to guide the kneecap centrally, predisposing to maltracking, dislocation, and early arthritis.
- Repetitive high knee-flexion loading. Occupations and sports involving prolonged kneeling, squatting, stair climbing, or heavy cycling apply repeated high compressive loads to the patellofemoral joint and are associated with earlier onset of arthritis.
- Female sex. The wider female pelvis creates a greater Q-angle (the angle between the quadriceps force vector and the patella tendon), which increases lateral patellar tracking forces and is a recognised risk factor for patellofemoral arthritis.
- BMI over 29. The patellofemoral joint bears forces of three to five times body weight during stair climbing; excess body weight amplifies these forces substantially.
- Previous anterior knee surgery. Tibial tubercle osteotomy, patella tendon surgery, or prior arthroplasty can alter patellar tracking and predispose to patellofemoral arthritis.
How is patellofemoral arthritis diagnosed?
Clinical examination identifying anterior knee pain and a positive patellar grind test, combined with a sunrise (Merchant) or skyline view X-ray specifically imaging the patellofemoral joint, is the foundation of diagnosis. MRI maps cartilage loss precisely and distinguishes isolated patellofemoral disease from multi-compartment arthritis before treatment planning.
Mr Hussain will assess the character and location of knee pain, functional limitations, and perform a structured examination including the patellar grind test, apprehension test, and assessment of patellar tracking throughout the range of motion. Imaging investigations include:
- Sunrise (Merchant) or skyline view X-ray. A dedicated patellofemoral view taken with the knee flexed to 30 or 45 degrees, enabling direct visualisation of the patellofemoral joint space, patellar tilt, and trochlear morphology. This view can appear normal on standard AP and lateral films, so must be specifically requested when patellofemoral arthritis is suspected.
- Standard AP and lateral X-rays. Weight-bearing films assess the medial and lateral compartments and identify any associated tibiofemoral arthritis, which is crucial to surgical planning.
- MRI. Characterises cartilage loss on the patellar and trochlear surfaces, identifies subchondral bone changes, and maps the extent of disease. Essential for younger patients and when surgical planning requires precise compartment mapping before deciding between patellofemoral arthroplasty and total knee replacement.
- Long-leg alignment film. Required before any knee replacement surgery to measure limb alignment and plan implant positioning.
Can patellofemoral arthritis be treated without surgery?
Yes, for mild to moderate disease. Quadriceps strengthening, patellar taping, bracing, anti-inflammatory medication, and steroid injection can provide significant relief. Avoiding activities that repeatedly load the patellofemoral joint (stairs, cycling in high gear, deep squats) reduces symptoms. Surgery is considered when conservative measures fail to adequately control pain.
Non-surgical management is effective for many patients, particularly those with Grade 1 to 2 patellofemoral arthritis. Key components include:
- Quadriceps and VMO strengthening. Strengthening the vastus medialis oblique (VMO) muscle, which pulls the kneecap medially, improves patellar tracking and reduces stress on the lateral cartilage. Straight-leg raises, mini-squats, and step-ups in a limited range (0 to 45 degrees of flexion) are well-tolerated and effective.
- Patellar taping (McConnell technique). A strip of firm tape applied medially across the kneecap corrects lateral tilt and reduces pain during exercise for many patients. Physiotherapy-guided application is more effective than self-applied taping.
- Knee bracing. A patellar tracking brace with a lateral buttress pad reduces lateral patellar forces and can allow return to activities that would otherwise be too painful.
- Activity modification. Reducing stair use, avoiding prolonged kneeling and squatting, and switching from hill walking to flat surfaces significantly reduces patellofemoral load. Cycling in a high gear (low cadence) concentrates load on the kneecap; switching to a lower gear (high cadence) is better tolerated.
- Anti-inflammatory medication and injection. Topical NSAIDs and oral anti-inflammatories reduce joint inflammation. An intra-articular corticosteroid injection can provide 4 to 12 weeks of targeted relief and facilitate a physiotherapy programme.
- Weight loss. Even modest weight reduction measurably reduces patellofemoral joint loading during stair climbing and improves surgical outcomes if replacement becomes necessary.
What surgery is available for patellofemoral arthritis?
Total knee replacement is the most commonly performed operation for patellofemoral arthritis presenting to Mr Hussain, as most patients have some degree of concurrent medial compartment arthritis. Isolated patellofemoral arthroplasty is considered for the minority of patients with strictly isolated patellofemoral disease with intact medial and lateral cartilage.
The surgical decision depends on whether arthritis is genuinely isolated to the patellofemoral compartment or whether medial and lateral cartilage is also affected. MRI and careful examination of X-rays, combined with clinical findings, determine the right operation for each individual patient.
Patellofemoral Arthroplasty
Patellofemoral joint replacement resurfaces only the kneecap and trochlear groove, preserving the medial and lateral compartments and both cruciate ligaments entirely. It offers faster recovery than total knee replacement and a more naturally-feeling knee. However, strict patient selection is required: the medial and lateral cartilage must be intact, and the cruciate ligaments must be functional.
- Suitable only for isolated patellofemoral arthritis
- Preserves healthy medial and lateral compartments
- Faster recovery than total knee replacement
- Revision to total knee replacement possible if other compartments later deteriorate
- Mr Hussain carefully selects patients using MRI and examination
Total Knee Replacement
When patellofemoral arthritis is accompanied by medial or lateral compartment involvement (which is the case in the majority of patients), total knee replacement is the standard surgical treatment. Robotic-assisted surgery allows precise implant positioning tailored to each patient's anatomy, including careful attention to patellar tracking and resurfacing.
- Appropriate when multi-compartment arthritis is present
- Robotic-assisted (MAKO, ROSA, CORI) for precision alignment
- Patella resurfacing decision made individually based on findings
- Most patients mobilising the same day as surgery
- Day-case surgery available for suitable patients
How successful is knee replacement for patellofemoral arthritis?
Knee replacement reliably relieves the anterior knee pain of patellofemoral arthritis. National Joint Registry data shows approximately 90 per cent of total knee replacements are still functioning at 15 years. Robotic-assisted surgery improves implant positioning accuracy and is expected to improve long-term outcomes further.
Careful surgical technique in managing the patella is important in knee replacement for patellofemoral arthritis. The decision to resurface the patella (replace the cartilage surface of the kneecap with a polyethylene button) is made individually based on the severity of patellar cartilage damage, patellar thickness, and tracking characteristics. Mr Hussain makes this decision during surgery based on direct inspection of the joint.
Robotic assistance allows the surgeon to plan patellar component sizing and positioning preoperatively and to optimise the alignment of all three components to achieve balanced patellofemoral tracking. This is particularly important for patients with prior patellar maltracking, where achieving correct patellar tracking is critical to a good outcome.
Expertise in knee arthritis treatment in Birmingham
Consultant at the Royal Orthopaedic Hospital
Mr Hussain practises at the Royal Orthopaedic Hospital Birmingham, one of the largest specialist orthopaedic hospitals in Europe, alongside Priory Hospital Edgbaston and Harborne Hospital.
3,000+ arthroplasty cases
From a total of more than 5,000 procedures performed, giving the operative volume and case complexity required for consistently excellent outcomes. Read more about Mr Hussain's training and background.
MAKO, ROSA, and CORI robotic certifications
Mr Hussain holds certifications on all three major robotic knee replacement platforms, allowing robotic-assisted surgery to be offered to all suitable patients regardless of which platform is available at their chosen hospital.
Complex revision surgery expertise
Mr Hussain performs revision knee replacement for patients whose primary replacement has failed, including those with previous patellofemoral surgery. See revision knee surgery for more information.
Doctify Outstanding Patient Experience 2024, 2025, and 2026
Awarded in three consecutive years, recognising consistently high patient-reported outcomes and communication throughout the surgical journey.
4.98 out of 5 from verified reviews on Doctify. Outstanding Patient Experience Award 2024, 2025, and 2026.
Frequently asked questions about patellofemoral arthritis
For more questions about surgery, recovery, fees, and what to expect, see the full frequently asked questions page or read recent patient testimonials.