Patellofemoral Pain and Patellar Instability (Kneecap Problems) in Bristol

Kneecap problems are among the most common – and most frequently mismanaged – conditions I see. Patellofemoral pain causes pain around or behind the kneecap, often worse on stairs, hills, squats, running, or after sitting with the knee bent. Patellar instability means the kneecap partially slips out of place (subluxation) or fully dislocates. These two problems overlap more often than people realise: a knee can be painful without dislocating, and instability itself causes pain, swelling, and loss of confidence.

The key to getting this right is treating the whole patellofemoral "system" rather than one structure in isolation. That means understanding the groove, the kneecap height, the alignment, the rotation, and the soft tissue restraints – and then building a plan around what is actually driving your symptoms.

What does the kneecap do?

The kneecap (patella) sits in a groove at the front of the thigh bone (the trochlea). It acts like a pulley for the quadriceps muscle, improving the efficiency of straightening the knee. The undersurface of the kneecap and the groove are lined with cartilage to allow smooth movement.

What is patellofemoral pain?

Patellofemoral pain describes pain generated from the front of the knee, usually related to overload or irritation in the kneecap joint. It can be caused by training errors, muscle weakness, poor movement control, tightness, overuse, cartilage wear, or subtle alignment issues. It does not automatically mean arthritis or "damage," and many people improve substantially with the right rehabilitation.

What is patellar instability?

Patellar instability occurs when the kneecap does not stay centred in the groove during movement. It can range from:

Subluxation: the kneecap partially shifts out of place then slides back
Dislocation: the kneecap fully comes out of the groove and usually needs to be relocated

Instability may happen after a single traumatic event, or recur due to underlying anatomy (such as a shallow groove, malalignment, or high-riding kneecap).

Common causes and contributing factors

Patellofemoral pain and instability are almost always multifactorial. Key contributors can include:

Muscle weakness or poor control – hip, gluteal, and quadriceps control affecting kneecap tracking
Overuse and training load – rapid increases in running, hills, stairs, squats
Patella alta – a high-riding kneecap
Trochlear dysplasia – a shallow or misshapen groove
Increased TT–TG distance – the tendon line of pull sits too far to the outside, encouraging lateral tracking
Rotational alignment issues – femoral anteversion, tibial torsion
Valgus alignment (knock-knee) or other alignment patterns affecting the joint line
Ligament injury, especially of the MPFL after a dislocation
Fat pad impingement – pinching and inflammation of the soft tissue below the kneecap

Symptoms

Patellofemoral pain symptoms

Pain behind or around the kneecap, often worse with stairs, hills, squatting, lunging, running, or prolonged sitting
Grinding or creaking sensations (sometimes)
Swelling after activity (sometimes)
Tenderness at the front of the knee

Patellar instability symptoms

A feeling the kneecap "shifts," "slips," or is about to dislocate
Giving-way episodes with twisting or sudden direction changes
Swelling after an event, often rapidly if a true dislocation occurs
Apprehension or fear with certain positions (for example when the knee is bent and the kneecap is pushed sideways)

Fat pad impingement symptoms

Sharp or aching pain at the front of the knee, often just below the kneecap
Pain when fully straightening the knee or standing with the knee "locked back"
Localised tenderness and swelling at the front of the joint

Assessment and diagnosis

Getting kneecap problems right requires identifying which factor is driving symptoms: overload, tracking, instability, anatomy, or a combination. I take a detailed history – dislocation events, pain triggers, swelling pattern, sport and work demands, and previous treatments – followed by a thorough examination of kneecap tracking, tenderness, stability, range of motion, hip control, and movement quality.

X-rays assess patella position, joint surfaces, and alignment. MRI shows cartilage, MPFL injury, bone bruising, and fat pad inflammation. In some cases I request CT or specialist imaging to quantify alignment measures and rotational profile – this is particularly useful when I suspect torsion is a significant contributor.

The goal is a diagnosis that explains the symptoms and supports a plan that is predictable and durable.

First-line treatment: physiotherapy and load management

For many people, the most effective first step is a structured rehabilitation programme. This is particularly true for patellofemoral pain without recurrent dislocation.

Physiotherapy focus

Hip and glute strength – improves limb control and reduces kneecap overload
Quadriceps strength – especially functional control through range
Movement retraining – squat, step, and running mechanics
Flexibility and soft tissue control where relevant
Load progression – gradual return to hills, stairs, and running

Other non-surgical options

Taping or bracing for symptom control
Short-term anti-inflammatory medication if appropriate
Activity modification to calm flare-ups
Targeted injections, used cautiously and only when clearly helpful

If symptoms persist, or if there is true recurrent instability, surgical options may be considered based on the underlying anatomy.

Understanding key terms

Patella alta (high-riding kneecap)

Patella alta means the kneecap sits higher than usual. This can reduce the time the kneecap is engaged within the groove during early bending, increasing the risk of instability and sometimes contributing to pain. It can be:

Static patella alta: the kneecap sits high on imaging even at rest
Dynamic patella alta: the kneecap rides higher when the leg is loaded, affecting engagement of the kneecap in the groove as the knee begins to bend from a straightened position

TT–TG distance

The TT–TG distance describes how far the patellar tendon attachment sits from the centre of the groove. If it is relatively lateral, the line of pull can encourage the kneecap to track outward, contributing to instability. However – and this is important – the latest evidence suggests TT–TG is less relevant and can be misleading as a standalone measure, especially in the context of dysplasia, alta, and rotational problems in the limb. I see patients who have been told their TT–TG is "normal" when the real driver is torsion, and others who have been offered surgery for a "high" TT–TG that is actually an artefact of the way the measurement interacts with rotation. It is one piece of the puzzle, not the whole picture.

Trochlear dysplasia

Trochlear dysplasia means the groove the kneecap should sit in is shallow or misshapen, reducing stability – particularly in early knee flexion.

Rotational alignment (torsion)

Rotational alignment refers to twist in the thigh bone (femur) or shin bone (tibia). Excess femoral anteversion or tibial torsion can change how the kneecap tracks and increase lateral forces. This is an increasingly recognised driver of instability and one I assess carefully with specialist imaging when the clinical picture suggests it.

Surgical options: stabilisation and realignment

Surgery is tailored to the cause. Some patients need soft-tissue stabilisation and balancing, some need bony realignment, and some need a combined approach. I plan each case individually.

MPFL reconstruction (kneecap stabilisation)

The medial patellofemoral ligament (MPFL) is the main soft-tissue restraint preventing the kneecap from dislocating laterally in early knee bending. It is commonly torn during a dislocation.

MPFL reconstruction rebuilds this restraint, usually using a tendon graft, to reduce the risk of recurrent dislocation. I consider it for:

Recurrent patellar instability (repeated subluxations or dislocations)
Persistent instability symptoms with an anatomical risk profile
First-time dislocations where the anatomy suggests a high risk of recurrence or there is associated cartilage injury

MPFL reconstruction can be performed alone when the bony anatomy is favourable, but if major bony risk factors are present (such as patella alta or significant malalignment), combining procedures tends to be more predictable and durable.

Osteotomy and bony realignment (when mechanics drive the problem)

Osteotomy means reshaping bone to change alignment and load. In patellofemoral problems, I consider osteotomy when alignment, patella height, or rotational profile is a major driver of pain or instability.

Tibial Tubercle Osteotomy (TTO)

A tibial tubercle osteotomy repositions the bony attachment of the patellar tendon. This can change kneecap tracking, reduce lateral pull, and lower a high-riding kneecap.

I consider TTO when:

There is patella alta contributing to instability (both static and dynamic forms)
There is a lateralised tendon line of pull contributing to maltracking or instability
There is focal cartilage wear where unloading a specific area may help

In simple terms, TTO helps the kneecap engage the groove earlier, track more centrally, and reduce overload.

Distal Femoral Osteotomy (DFO)

A distal femoral osteotomy corrects alignment at the lower thigh bone. It is most relevant when knock-knee alignment (valgus) increases lateral forces across the knee and worsens patellofemoral symptoms or contributes to instability patterns.

I consider DFO when:

Valgus (knock-knee) alignment is a key driver of symptoms
There is lateral compartment or lateral patellofemoral overload linked to alignment

High Tibial Osteotomy (HTO)

A high tibial osteotomy corrects alignment at the upper shin bone. It is most often used for bow-leg alignment (varus) with medial compartment overload, but it can also be relevant in broader knee-preservation planning when overall limb mechanics contribute to symptoms.

I consider HTO when:

Varus (bow-leg) alignment is contributing to overload elsewhere in the knee
Knee mechanics need rebalancing as part of a combined preservation strategy

Rotational osteotomy (torsional correction)

A rotational osteotomy corrects abnormal twist in the femur or tibia. I consider it when rotational alignment is a major driver of maltracking or instability and symptoms persist despite excellent rehabilitation.

Rotational osteotomy may be appropriate when:

There is significant femoral anteversion or tibial torsion contributing to lateral tracking forces
Instability persists and the rotational profile strongly supports torsion as a driver

Rotational correction is a major decision. I reserve it for carefully assessed cases where imaging and symptoms clearly align, and where other approaches have not addressed the underlying problem.

Trochleoplasty (improving the groove)

Trochleoplasty reshapes the trochlear groove to improve kneecap containment. It is not a routine procedure for patellofemoral pain alone. I consider it for recurrent patellar instability where there is significant trochlear dysplasia and the groove shape is a key reason the kneecap dislocates.

Where appropriate, trochleoplasty may be combined with MPFL reconstruction and/or tibial tubercle osteotomy to address multiple risk factors in a single operation.

Fat pad impingement: what it is and how it's treated

The infrapatellar fat pad is a sensitive soft tissue structure beneath the kneecap. If it becomes inflamed or pinched (impinged), it can cause sharp anterior knee pain, especially when fully straightening the knee or standing with the knee locked back.

Treatment often includes:

Physiotherapy to improve movement control and reduce pinching positions
Load modification and activity pacing
Anti-inflammatory strategies when appropriate
Targeted injection or arthroscopic management where the fat pad is the primary pain driver and non-surgical care has not been enough

Recovery and rehabilitation

Rehabilitation is essential in both non-surgical and surgical pathways. The plan depends on which procedure (or combination) is performed.

Typical aims of rehabilitation

Control swelling and restore movement
Rebuild strength (quadriceps, glutes, hips) and movement quality
Improve kneecap control and confidence in higher-demand tasks
Progressively return to running and sport when safe

Procedures such as MPFL reconstruction, TTO, trochleoplasty, or osteotomy have protective phases early on, followed by progressive strengthening and functional retraining. I individualise the programme based on anatomy, healing, and goals.

Risks and limitations

All surgery carries risks. The exact risks depend on the procedure performed. Potential issues include:

Infection, blood clots, stiffness, or prolonged swelling
Ongoing pain or incomplete symptom improvement
Recurrent instability if underlying drivers are not fully addressed
Hardware irritation after bony procedures (such as TTO or osteotomy)
Cartilage wear progression over time in some knees

I discuss the expected benefits, alternatives, likely rehabilitation course, and the specific risks relevant to your knee in clinic.

Frequently asked questions

What's the difference between patellofemoral pain and patellar instability?

Patellofemoral pain is primarily pain from the kneecap joint, often related to overload and movement mechanics. Patellar instability is when the kneecap partially or fully slips out of position. Some people have both, and the assessment is designed to tease apart what is driving symptoms.

Do I always need surgery if I dislocate my kneecap?

Not always. Treatment depends on whether the dislocation is a first-time event or recurrent, whether there is associated cartilage injury, and whether your anatomy suggests a high risk of it happening again. Many people start with physiotherapy, but recurrent instability often needs surgical stabilisation. I work closely with specialist physiotherapists who have expertise in the full scope of patellofemoral rehabilitation.

When would a tibial tubercle osteotomy (TTO) be considered?

I consider TTO when kneecap position and tendon mechanics are a key driver – typically with patella alta (static or dynamic), maltracking patterns, or instability risk factors. It is often used alongside ligament stabilisation procedures.

What does MPFL reconstruction do?

It rebuilds a key ligament on the inner side of the knee that prevents the kneecap dislocating outward. I use it commonly for recurrent instability, either alone or combined with bony procedures when the anatomy requires it.

When is trochleoplasty used?

Trochleoplasty is typically reserved for recurrent instability when the groove shape (trochlear dysplasia) is a major driver. I do not perform it for pain alone.

When is a knee brace needed?

A knee brace is not always needed for patellofemoral pain or kneecap instability, but it can help in specific situations – protecting healing tissues, supporting safer movement, and reducing re-injury risk while strength and control return. After a tibial tubercle osteotomy, I commonly use a brace in the first 4–6 weeks because pain and swelling can temporarily inhibit the quadriceps, making the knee feel like it may "give way" during weight-bearing. The brace provides stability while physiotherapy rebuilds quadriceps control, and I adjust the amount of allowed knee bend and duration of bracing based on the procedure and your progress.

Can I be assessed for patellofemoral pain or kneecap instability in Bristol?

Yes. I offer specialist patellofemoral assessment in Bristol, including physiotherapy-led care, imaging-based diagnosis, and the full range of surgical options when appropriate.