Patella / patellofemoral system

Anatomy: patella, plain bearings and guide

The patella is a sesamoid bone in the quadriceps tendon. It runs in the V-shaped trochlea of ​​the femur and increases the lever arm of the knee extensor muscles. A complex interplay of bone shape, cartilage, ligaments and muscles stabilizes the kneecap and enables low-friction guidance.

• Bone/Cartilage: Patella with medial/lateral facet; Trochlea with variable depth (dysplasia possible).
• Passive stability: Medial patellofemoral ligament (MPFL), medial/lateral retinacula, capsule.
• Active stability: quadriceps (especially vastus medialis and lateralis muscles), patellar tendon, pelvic/hip muscles.
• Plain bearings: cartilage and synovium reduce friction; Incorrect loading leads to irritation.

Shape variants such as trochlear dysplasia, patella alta/baja or axial deviations influence the directional stability of the patella (tracking) and can cause problems.

Function and kinematics

When bending and extending, the patella slides in the trochlea and transmits high forces. The contact pressure increases with increasing flexion and load (e.g. stairs, squatting). The alignment of the leg axis, the Q-angle geometry and neuromuscular control determine how centrally the patella is guided.

• Dynamic control: Hip abductors/external rotators stabilize the knees and pelvis.
• Valgus/Internal Rotation Pattern: Increase lateral traction and patellar maltracking.
• Load management: Steep increases in training volume/intensity promote overload.

Typical complaints and warning signs

Patellofemoral problems often manifest as anterior knee pain, a feeling of instability or buckling, and stress-related irritation. Depending on the trigger, the intensity, location and accompanying symptoms vary.

• Front knee pain when descending stairs, squatting, or sitting for long periods (“theatrical signs”).
• Rubbing, grinding, snapping without blockage mostly harmless; new and painfully in need of clarification.
• Feeling of instability/dislocation, especially when changing direction.
• Swelling/effusion after stress or trauma.
• After acute dislocation: significant pain, bleeding, inhibition of knee extension.

Causes and risk factors

Anterior knee pain usually arises from an interplay of overload, biomechanics and individual anatomy. Systemic or inflammatory causes are rarely involved.

• Shape variants: trochlear dysplasia, patella alta, increased TT–TG distance.
• Soft tissues: Ligament laxity, insufficient MPFL (e.g. after dislocation), tight lateral retinaculum.
• Dynamics: hip/leg axis control (dynamic valgus), foot pronation, trunk stability.
• Training: Sudden increase in load, monotonous stress, inadequate regeneration.
• Trauma: initial dislocation with MPFL lesion; Bony/cartilaginous accompanying injuries possible.
• Growth/Development: Adolescents with open growth plates have special risk profiles.

Diagnostics: step by step

The diagnosis is based on anamnesis, clinical examination and, if necessary, imaging tests. The aim is to identify treatable stress factors and structural risks.

• History: Pain provocation (stairs, squatting), moments of instability, training course, initial event.
• Clinic: Patellar sliding test/apprehension, medial/lateral translation, tracking analysis (single-leg squat), retropatellar pressure pain points.
• Axis and foot status: pelvic/hip control, dynamic valgus, pronation.
• X-ray: AP, lateral (patella level), axial image (Merchant/Sunrise) for patellar alignment.
• MRI: cartilage/bone marrow edema, MPFL lesion, associated injuries.
• CT (targeted): rotation/torsion analysis, TT–TG distance during surgery planning.
• Sonography: soft tissue assessment, effusion; dynamically helpful to a limited extent.

Not every anterior knee pain symptom requires immediate imaging. In the case of persistent complaints, instability or after trauma, it is useful in order to safely plan therapy paths.

Conservative therapy: foundation of treatment

Most patellofemoral complaints respond to structured, active conservative treatment. The central goals are pain relief, normalization of tracking and gradual increase in load.

• Education & Load Management: Temporarily dose irritating activities; gradual increase.
• Physiotherapy: Strengthening hip abductors/external rotators and quadriceps; neuromuscular control.
• Flexibility: Stretching lateral retinaculum/IT band, quadriceps, hamstrings, calves.
• Motor skills/gait school: knee-over-foot position, stride width, cadence (for runners).
• Taping/orthosis: Patellar taping (e.g. McConnell) or patella-stabilizing bandage for short-term relief.
• Insoles: For severe overpronation to distribute the load; check individually.
• Acute measures: cooling, short-term anti-inflammatory strategy after medical consideration.
• Return-to-Activity: Step-by-step plan with stress tests (e.g. stairs, squatting, hop tests) as feedback.

Injections and regenerative options (selected)

Injection therapies can support conservative rehabilitation in individual cases. They do not replace active therapy. We discuss benefits, limitations and evidence individually and avoid overtreatment.

• Hyaluronic acid: possible as a viscoelastic supplement for patellofemoral osteoarthritis; Effect individual.
• PRP (platelet-rich plasma): Can be an additional option for localized cartilage irritations; Evidence heterogeneous.
• Shock wave: More likely in patellar tendon irritation than in pure patellofemoral pain; Check indication.

Important: Injections are carried out according to clear indications, a sterile procedure and in combination with exercise therapy adapted to the load.

Surgical options: targeted and indication-based

Surgery is considered when conservative measures have been exhausted and relevant structural risk factors or repeated dislocations are present. The decision is based on imaging, functional findings and individual goals.

• MPFL reconstruction: Restoration of medial suspension in cases of instability.
• Tibial tuberosity displacement (TT displacement/Fulkerson): Correction for increased TT–TG or maltracking.
• Trochleoplasty: For severe trochlear dysplasia in selected cases.
• Lateral Release/Retinaculum Procedures: Not isolated; only as part of an overall concept.
• Cartilage therapies: microfracture/chondroplasty/cartilage cell procedures depending on the defect pattern.
• Derotation osteotomy: Rare, for severe torsional deformity after careful analysis.

Even after surgery, rehabilitation remains crucial. We plan follow-up treatment and stress build-up in a structured and close-meshed manner.

Prevention and independent training

• Regular strength training of the hip and core muscles.
• Technique training: knee-over-foot alignment in squats, landings and changes of direction.
• Progression: gradually increase training loads, plan breaks.
• Footwear/Insoles: Adapt to the specific sport and individually.
• Variability: incorporate different movements/loads, avoid monotony.

Rehabilitation and return to sport

The duration of recovery varies with trigger, training condition and goal level. Function-based milestones instead of fixed calendar dates are crucial.

Special features for children and young people

During growth phases, soft tissues and bone structures are adaptable but sensitive to overload. Axis guidance and motor control are still developing - this can lead to patellar problems.

• Gentle stress build-up, technique training and varied movement.
• Surgical planning takes into account open growth plates; Bone-sparing procedures are preferred.
• Good prognosis with early, consistent conservative therapy.

When should I seek medical advice?

• Acute patellar luxation, inability to straighten or put weight on the knee.
• Severe swelling/effusion after trauma.
• Feeling of blockage, entrapment, persistent feeling of instability.
• Persistent pain >6–8 weeks despite adjusted load.
• Fever, redness, night pain or pain at rest with no apparent cause.

Subtopics at a glance

The following pages delve into typical clinical pictures and adjacent structures of the knee joint:

• Patellar luxation – acute dislocation of the kneecap: causes, first aid, treatment options.
• Recurrent patellar dislocation – recurrent instability: risk factors, stabilization strategies.
• Patellofemoral pain syndrome – anterior knee pain without a structural main cause: training and everyday tips.
• Patellar maltracking – wrong track of the kneecap: diagnostics and conservative correction.
• Muscles, tendons, ligaments – influence of soft tissues on patellar guidance.
• Joint, cartilage, synovium – cartilage health in the patellofemoral plain bearing.
• Meniscus – differential diagnosis for anterior/anterolateral pain.
• Cruciate ligaments and instability – overall knee joint stability in context.
• Bones/Structure – Axes, torsion and their role in tracking.
• Trauma / Acute Injuries – Diagnosis after a sports accident.
• Systemic/inflammatory causes – when more than mechanics play a role.
• Functional / chronic pain syndromes – pain processing and training.

Your supply in Hamburg

We combine modern diagnostics with evidence-based, conservative orthopedics. After a detailed anamnesis and examination, we will create an individual plan with you: physiotherapy with clear exercise goals, load management, technique and running analysis, taping/orthosis if necessary and - only if appropriate - injection or surgical options. Our location: Dorotheenstraße 48, 22301 Hamburg.

The goal is sustainable knee health that is suitable for everyday use and sports without unnecessary interventions. We discuss opportunities and limitations transparently and include your goals (everyday life, leisure time, competitive sports) in the planning.