Patellofemoral joint degeneration: A review of current management

Published:November 12, 2021DOI:https://doi.org/10.1016/j.jcot.2021.101690

      Abstract

      The patellofemoral component of the knee joint is affected by a wide range of degenerative causes without involving the other parts of the knee. It is often the presenting pathology in early knee osteoarthritis and missed due to a variable presentation. Accurate examination and focused investigation can help with early diagnosis and guide treatment. Various aspects to treatment need to be addressed after thorough evaluation. Guidelines to approach the multifactorial pathology of the patello-femoral joint are provided with focus on the degenerative component of disease.

      Keywords

      1. Introduction

      Anterior knee pain or patellofemoral pain is one of the commonest diagnoses in young individuals with knee pain, estimated to affect 3–6% of the population.
      • Gaitonde D.Y.
      • Ericksen A.
      • Robbins R.C.
      Patellofemoral pain syndrome.
      ,
      • Lankhorst N.E.
      • Bierma-Zeinstra S.M.A.
      • van Middelkoop M.
      Risk factors for patellofemoral pain syndrome: a systematic review.
      Patellar cartilage lesions are among the most frequent pathologies found at knee arthroscopy.
      • Curl W.W.
      • Krome J.
      • Gordon E.S.
      • Rushing J.
      • Smith B.P.
      • Poehling G.G.
      Cartilage injuries: a review of 31,516 knee arthroscopies.
      Chondromalacia patellae is often used as a catchall term to describe any clinical presentation of patellar pathology, though chondropathy might be more accurate.
      • Habusta S.F.
      • Coffey R.
      • Ponnarasu S.
      • Griffin E.E.
      Chondromalacia patella.
      With the establishment of viable cartilage regeneration techniques, there is a growing need to differentiate early chondropathy, that is amenable to cure, from established arthritis where the inflammation associated with complete loss of cartilage makes way for treatment with salvage procedures.

      Techniques in Cartilage Repair Surgery | A. Ananthram Shetty | Springer [Internet]. [cited 2021 May 29]. Available from: https://www.springer.com/gp/book/9783642419201.

      Though patellar chondropathy and arthritis are considered to be on the same disease spectrum, there is debate on whether patellofemoral arthritis can be an isolated entity from general knee osteoarthritis.
      • Insall J.N.
      Patella pain syndromes and chondromalacia patellae.
      Arthritis of this compartment is certainly more prevalent than that of the tibio-femoral compartment in middle-aged people.
      • Hinman R.S.
      • Lentzos J.
      • Vicenzino B.
      • Crossley K.M.
      Is patellofemoral osteoarthritis common in middle-aged people with chronic patellofemoral pain?.
      There is a suggestion that patellofemoral pain syndrome would eventually lead to arthritis of that joint.
      • Crossley K.M.
      Is patellofemoral osteoarthritis a common sequela of patellofemoral pain?.
      ,
      • Eijkenboom J.F.A.
      • Waarsing J.H.
      • Oei E.H.G.
      • Bierma-Zeinstra S.M.A.
      • van Middelkoop M.
      Is patellofemoral pain a precursor to osteoarthritis?: patellofemoral osteoarthritis and patellofemoral pain patients share aberrant patellar shape compared with healthy controls.
      Innate and acquired causative factors lead to the development of patellofemoral pain. Innate factors include adolescent patellar instability and a range of subtle malalignment or kinematic alterations in the patellofemoral joint that lead to joint degeneration and symptoms in early adulthood or middle-aged years.
      • Lankhorst N.E.
      • Bierma-Zeinstra S.M.A.
      • van Middelkoop M.
      Risk factors for patellofemoral pain syndrome: a systematic review.
      ,
      • Petersen W.
      • Ellermann A.
      • Gösele-Koppenburg A.
      • et al.
      Patellofemoral pain syndrome.
      Trauma, disuse and overuse are acquired factors that could either cause isolated patellofemoral degeneration independently or add to the insult caused by aberrant kinematics.
      • Coggon D.
      • Reading I.
      • Croft P.
      • McLaren M.
      • Barrett D.
      • Cooper C.
      Knee osteoarthritis and obesity.
      ,
      • Dixit S.
      • DiFiori J.P.
      • Burton M.
      • Mines B.
      Management of patellofemoral pain syndrome.
      In recent years, obesity is a rising cause of anterior knee pain amongst the youth.
      • Coggon D.
      • Reading I.
      • Croft P.
      • McLaren M.
      • Barrett D.
      • Cooper C.
      Knee osteoarthritis and obesity.
      This in turn could stem from lifestyle or endocrine related causes that also result in weaker lower limb musculature. Trauma to the patellar cartilage is often neglected when it occurs as a part of other bony or ligamentous injuries of the knee. Cartilage lesions are often discovered incidentally with high quality comprehensive imaging, at operation for other causes or when the degeneration has advanced. Similarly, self-treatment with braces for the knee is common, which has the consequent potential of leading to a vicious cycle of disuse and related wear of the joint. There is no evidence that kneeling and squatting lead to degeneration of the patellar cartilage amongst people who need these activities in their profession. However, avoidance of such postures is rampant amongst young adults with anterior knee pain, and often reinforced by medical practitioners too, further adding to the patients’ disability. The authors present a comprehensive summary for the management of patellofemoral degeneration.

      2. Clinical assessment

      Comprehensive assessment of patellar degeneration is often challenging. Management decisions need to be made with a combination of patient history, clinical examination and relevant investigations.
      • van Jonbergen H.-P.W.
      • Poolman R.W.
      • van Kampen A.
      Isolated patellofemoral osteoarthritis.
      Degeneration of the patellar cartilage can occur at a relatively younger age. Younger adults presenting with symptoms must be carefully evaluated for subtle malalignments, dysplasia and instability. In the older age group, anterior knee pain is often the first presentation of generalized knee osteoarthritis. Presentation of patellar problems is varied but the commonest symptom reported is usually pain associated with flexion.
      • Gaitonde D.Y.
      • Ericksen A.
      • Robbins R.C.
      Patellofemoral pain syndrome.
      Other common complaints include difficulty getting up from sitting, especially from lower heights, negotiating stairs and decreased confidence in flexion activities like stairs (going downstairs is usually more difficult than upstairs as going down requires more flexion), kneeling and squatting with the pain often not well-localized.
      • Rathleff M.S.
      • Roos E.M.
      • Olesen J.L.
      • Rasmussen S.
      • Arendt-Nielsen L.
      Lower mechanical pressure pain thresholds in female adolescents with patellofemoral pain syndrome.
      Most describe a long history with intermittent treatments having been taken that resulted in temporary cure. Recent weight gain related to activity or other illnesses (often undetected endocrine cause) must be investigated. Clinical findings must be interpreted relative to the other compartments of the knee. There is a high component of sensitivity for pathologies of the patella as compared to that of any other structure in the knee joint.
      • Jensen R.
      • Hystad T.
      • Baerheim A.
      Knee function and pain related to psychological variables in patients with long-term patellofemoral pain syndrome.

      2.1 Physical examination

      It is always desirable to expose the whole lower limb and commence with examination of the opposite side so as to establish a baseline that may be normal. Knee varus/valgus and the weight bearing subtalar joint evaluation should be carried out in the posterior view. Gait patterns should be observed: waddle due to weak abductors from knee OA is common. Other patterns that can be picked up here are features of malalignment as above and features of antalgic or stiff knee. Certain measurements can be made such as leg length and Q angle (Fig. 1a and b).
      Fig. 1
      Fig. 1(From left to right) Anterior and lateral bilateral full leg view.
      Q – angle is from between a line drawn from the anterosuperior iliac spine to the midpoint of the patella and a line drawn from the tibial tubercle to the midpoint of the patella. The angle ranges between 8 and 12° in males and 15–18° in females. A greater Q-angle in women may partly explain higher incidences of patellofemoral pain in women. An excessive Q angle causes an added biomechanical stress such as, excessive pronation of the foot, excessive internal rotation of the tibia which will alter the quadriceps mechanism and patella tracking, eventually leading to degenerative joint disease.
      Abnormal tibial torsion is a common problem that may significantly impact muscle lever arms and force production. The patient is made to lie prone with the knee flexed to 90° and the ankle in neutral position. Tibial torsion is measured as the angle between a line connecting the centres of the medial and lateral malleoli (transmalleolar axis, TMA) and a line perpendicular to the long axis of the thigh. The normal torsional angle is found to be approximately 20°.

      2.2 Dynamic movement assessment:
      • Manske R.C.
      • Davies G.J.
      Examination OF the patellofemoral joint.

      2.2.1 Seated examination

      Passive and active patellar tracking: With the patient sitting, the clinician extends the knee from 90° flexion and observes for the tracking of the patella. When the test is conducted actively, attention should be paid between 20 and 30° of flexion to full extension, as this is the range in which most maltracking occurs.

      2.2.2 Standing examination

      A general gait assessment may not pick up minor issues. Activities placing greater demands on the knee joint should be incorporated as a part of examination process.
      • Step-down test: assess for the strength and endurance of the hip and leg, wherein the patient stands on a 20 cm box with the hands folded across the chest and squats down on one lower extremity 5–10 times slowly until the heel touches the floor.
      • Single – leg squat: Evaluates the dynamic hip and quadriceps strength. Subjects with PFA, may show, greater knee abduction, hip abduction, pelvic drop on the opposite side or same side trunk lean during this activity.
      Flexibility testing: for the quadriceps in prone position by Ely's test and for the iliotibial band in side lying using Ober's test.
      Functional testing: It is essential to determine, if a patient is safe to return to activity, for which an ergonomic or an ADL (activities of daily living) assessment is carried out.
      • 2-legged jump test – prepares the patient for concentric propulsive push off motion and eccentric deceleration landing phase.
      • Single-leg hop test – helps with eccentric land with deceleration in the involved side.
      • Lower Extremity Functional Test (LEFT) – Involves many lower extremity movement patterns which replicate activities of daily functional performance.

      3. Investigations

      Interpretation of patellar features on routine AP radiograph of the knee is impossible except provision of an idea of lateralization of the patella (provided there is no rotation) and ruling out accessory patella in case of lateral pain. However a long leg standing X-ray remains a standard vital primary investigation as it provides both an objective assessment of the axial alignment and also grades the affection of the tibio-femoral components of the knee joint. Axial mal-alignment must be within acceptable limits before addressing patellar pathology. Grading of patellofemoral osteoarthritis is traditionally described on the lateral radiograph. There is greater interest in interpreting the significance of degenerative findings on radiograph in recent times with the emergence of different joint-preserving therapeutic modalities.
      • Qiu Y.
      • Lin C.
      • Liu Q.
      • et al.
      Imaging features in incident radiographic patellofemoral osteoarthritis: the Beijing Shunyi osteoarthritis (BJS) study.
      When the floor of the trochlear groove rises above the top wall of one of the femoral condyles on the lateral radiograph, this is known as a ‘crossing sign’ and signifies a flat trochlea.
      • Wolfe S.
      • Varacallo M.
      • Thomas J.D.
      • Carroll J.J.
      • Kahwaji C.I.
      Patellar instability.
      Skyline or Merchant view of the knee is taken in 10,20 and 30° of knee flexion. The patient is lying supine near the edge of table. Xray beam is angled at 160° from the vertical axis and the patient holds the detector above the patella. This is an option in centres with no CT or MRI scan facilities.
      Highly sensitive modalities of investigations are single photon emission computed tomography (SPECT-CT) to detect subchondral bone metabolism in the patellofemoral joint and MRI scan which maps the cartilage in the patella and trochlea.
      • Ro D.H.
      • Lee H.-Y.
      • Chang C.B.
      • Kang S.-B.
      Value of SPECT-CT imaging for middle-aged patients with chronic anterior knee pain.
      ,
      • Rodrigues M.B.
      • Camanho G.L.
      Mri evaluation OF knee cartilage.
      A two-phase bone scintigraphy shows a nonspecific hypervascular osteoblastic focus in the knee between the patella and trochlea, which also includes the CT findings of patella as mentioned below. Hence providing a definitive source of pain focus, which can influence treatment options. A high field strength 1.5T MRI with a dedicated multi-channel knee coil has been shown to detect most chondral lesions.
      • Shetty A.A.
      • Kim S.J.
      • Shetty V.
      • Jang J.D.
      • Huh S.W.
      • Lee D.H.
      Autologous collagen induced chondrogenesis (ACIC: shetty-Kim technique) - a matrix based acellular single stage arthroscopic cartilage repair technique.
      MRI provides a good assessment of bony parameters (patellar height, trochlear dysplasia, patellofemoral congruence angle, distal insertion of quadriceps, tibial tuberosity-trochlear groove: TT-TGdistance) and soft tissue structures (MPFL, articular cartilage, chondral defects, extensor mechanism). Macri et al. have shown lower functional indices in patients with patellar pathologies and describe how assessment in 3D dynamic quadriceps evaluation is more useful than the traditional 2D imaging.
      • Macri E.M.
      • Crossley K.M.
      • Hart H.F.
      • et al.
      Clinical findings in patellofemoral osteoarthritis compared to individually-matched controls: a pilot study.
      . Patella engages the trochlear groove at 30° of flexion. Between 10 and 20° the lower most surface of medial and lateral facets engages the trochlea. Further flexion of the knee shifts the contact surfaces more proximal. Soft tissue and bony anatomy influence the stability of the patella. In centres with no access to dynamic CT scan, multiple repeated acquisitions at different degrees of flexion are obtained to provide a dynamic assessment. A multistage CT with a variable number of repeated acquisitions at different degrees of flexion can be performed to provide a dynamic assessment. An ideal dynamic CT scan would need to be undertaken during active functional tasks such as walking, stepping or squatting.
      • Muhle C.
      • Brossmann J.
      • Heller M.
      Kinematic CT and MR imaging of the patellofemoral joint.
      However, as this is not easily possible, isometric quadriceps contraction is employed during the undertaking of the scan, to recreate the forces acting on the patella during regular activities. Passive motion is insufficient to reproduce abnormal biomechanics of unstable joint
      • Brossmann J.
      • Muhle C.
      • Schröder C.
      • et al.
      Patellar tracking patterns during active and passive knee extension: evaluation with motion-triggered cine MR imaging.
      and imaging under static conditions can be misleading. Dynamic CT scan is undertaken by making the patient lie supine with a triangular firm pillow under the knee or an inflatable device which allows for continuous isometric contraction during range of knee flexion.
      • McNally E.G.
      • Ostlere S.J.
      • Pal C.
      • Phillips A.
      • Reid H.
      • Dodd C.
      Assessment of patellar maltracking using combined static and dynamic MRI.
      Knee is imaged as the knee is extended from 30° of flexion to full extension. The patient is given a brief training in the CT room and the technician ensures the patient has followed the instructions pertaining to quadriceps contraction (Fig. 2).
      Fig. 2
      Fig. 2Positioning the leg for dynamic CT scan.
      Measurements of patellar shift and tilt are taken from mid patellar transverse images (Fig. 3). The aim is to assess the patellar alignment just before the patella has engaged with the femoral sulcus at 20° of knee flexion:
      • Patellar Tilt: the angle between a line drawn parallel to another line (dotted line parallel to line AB in Fig. 3) connecting the medial and lateral posterior condyles makes an angle with the lateral facet of patella. This angle has to be greater than 7° in extension and 12-14° in 15° knee flexion. Decrease in this angle indicates maltracking of patella.
      • Sulcus angle: Two lines drawn along the medial and lateral border of trochlea converge at the deepest point (O in Fig. 3). The sulcus angle (COD in Fig. 3) is measured. Normal angle is 135 ± 10°. Angle more than 145-150° carries a higher risk of patella subluxation.
      • Patellar Shift: The sulcus angle above is bisected (E in Fig. 3). A point (R) is marked at the tip of patella and the index of subluxation is measured by this angle (further projected to F as in Fig. 3).
      • Patellar height: Various indices have been described of which the Insall- Salvati is most commonly used and measured on a lateral radiograph as shown in Fig. 4. It is calculated as a ratio of patella tendon length(TL)- length of the tendon measured from lower pole of patella to its insertion on the tibial tuberosity and patella length(PL) from superior to inferior pole of patella. The normal ratio is 0.8–1.2. If the ratio is less than 0.8, the condition is called patella alta or high riding patella and if ratio is more than 1.2, it is known as patella baja or low riding patella.
      Fig. 3
      Fig. 3Radiographic assessment of the patellofemoral joint
      (Key: alphabets described in the text, M & L denote medial and lateral dorsal femoral condyles respectively).

      4. Treatment

      The large prevalence of patellofemoral degeneration needs to be seen in relation to symptomatic affection of isolated patellar issues when determining treatment strategy for individual patients.
      • Kobayashi S.
      • Pappas E.
      • Fransen M.
      • Refshauge K.
      • Simic M.
      The prevalence of patellofemoral osteoarthritis: a systematic review and meta-analysis.
      Patellofemoral pathology when seen as an incidental finding during intervention for tibio-femoral compartment issues can often be retrospectively treated by conservative means. This article is limited to the management of primarily patellar wear-related problems.

      4.1 Non-operative treatment

      Conservative management of patellofemoral joint degeneration aims to reduce pain, increase strength, and improve the knee joint function. Pharmacological treatment with analgesics is a vital component of this. There have been recent developments of disease modifying osteoarthritic drugs but evidence for these remains limited.
      • Yang W.
      • Sun C.
      • He S.Q.
      • Chen J.Y.
      • Wang Y.
      • Zhuo Q.
      The efficacy and safety of disease-modifying osteoarthritis drugs for knee and hip osteoarthritis-a systematic review and network meta-analysis.
      Reduced strength of the quadriceps muscle is a predictor and risk factor for the development of patellofemoral degeneration.
      • Petersen W.
      • Ellermann A.
      • Gösele-Koppenburg A.
      • et al.
      Patellofemoral pain syndrome.
      Targeted exercises for the quadriceps muscle are crucial in rehabilitation programmes. Isometric exercises for the quadriceps can be initiated in the acute phases as it minimises the stress placed on the patellofemoral joint (PFJ) while reinforcing the quadriceps muscle. Closed kinetic chain exercises (CKC) are preferred over open kinetic chain exercises (OKC) within the limits of pain as they are usually more functional and particularly cause less stress at the patellofemoral joint.
      • Cohen Z.A.
      • Roglic H.
      • Grelsamer R.P.
      • et al.
      Patellofemoral stresses during open and closed kinetic chain exercises. An analysis using computer simulation.
      Specific exercises for the VMO (vastus medialis obliquus muscle) part of the quadriceps have been shown bring a change in the fibre angle of VMO and probably better minor alteration in the mechanics of the joint.
      • Benjafield A.J.
      • Killingback A.
      • Robertson C.J.
      • Adds P.J.
      An investigation into the architecture of the vastus medialis oblique muscle in athletic and sedentary individuals: an in vivo ultrasound study.
      Training of hip abductors in supine, or side lying is known to statistically and clinically improve the pain scores and functional outcomes.
      • Rogan S.
      • Haehni M.
      • Luijckx E.
      • Dealer J.
      • Reuteler S.
      • Taeymans J.
      Effects of hip abductor muscles exercises on pain and function in patients with patellofemoral pain: a systematic review and meta-analysis.
      An erect stable posture of the body is co-ordinated by the neuromuscular system. The spine, pelvis, hips, abdominal and gluteal regions are anatomically labelled as the core or muscular box. Irregularities in the control of this system of the body's core may influence the dynamic stability in the lower extremity. Core muscle strengthening hence needs to be a vital adjunct to traditional exercise regimes.
      • Hoglund L.T.
      • Pontiggia L.
      • Kelly J.D.
      A 6-week hip muscle strengthening and lumbopelvic-hip core stabilization program to improve pain, function, and quality of life in persons with patellofemoral osteoarthritis: a feasibility pilot study.
      Proprioception is known to regulate and activate the function of the muscles, which in turn stabilizes the joint producing a controlled movement. Exercises involving training on hard, soft and unstable surfaces are known to activate and challenge the proprioceptive receptors in the joint.
      • Nam C.-W.
      • Kim K.
      • Lee H.-Y.
      The influence of exercise on an unstable surface on the physical function and muscle strength of patients with osteoarthritis of the knee.
      These might prove beneficial in increasing the muscle strength and enhance physical function.
      • John Prabhakar A.
      • Joshua A.M.
      • Prabhu S.
      • Dattakumar Kamat Y.
      Effectiveness of proprioceptive training versus conventional exercises on postural sway in patients with early knee osteoarthritis - a randomized controlled trial protocol.
      This is especially in patients with patellar tracking issues who experience mild instability symptoms (Fig. 5).
      Fig. 4
      Fig. 4Insall-Salvati ratio. PL, Patella Length; TL,Tendon Length.
      Fig. 5
      Fig. 5From left to right (a) semi-squat with both leg support (b) Sitting on bobath and single leg support balance (c) Tandom standing (d) Standing on single leg, passing the ball to the team mate with trunk rotation.
      Taping of the patella is an alternative approach used for pain relief and might work in combination with exercise regimes.
      • Gigante A.
      • Pasquinelli F.M.
      • Paladini P.
      • Ulisse S.
      • Greco F.
      The effects of patellar taping on patellofemoral incongruence. A computed tomography study.
      Braces are similarly designed to promote hamstring activation and pain-free weight bearing activities by reducing the moment of compressive forces produced by the quadriceps.
      • Denton J.
      • Willson J.D.
      • Ballantyne B.T.
      • Davis I.S.
      The addition of the Protonics brace system to a rehabilitation protocol to address patellofemoral joint syndrome.
      Both these techniques might be used temporarily and during the undertaking of specific activities that aggravate symptoms. Contoured prefabricated orthoses can contribute to patella related pain relief and produce an ease in task performance in patients that have associated foot issues.
      • Barton C.J.
      • Munteanu S.E.
      • Menz H.B.
      • Crossley K.M.
      The efficacy of foot orthoses in the treatment of individuals with patellofemoral pain syndrome: a systematic review.
      Injection therapy with vissco-supplementation and platelet-rich plasma are widely used and have a documented safety profile but do not find mention in guidelines.
      • Clarke S.
      • Lock V.
      • Duddy J.
      • Sharif M.
      • Newman J.H.
      • Kirwan J.R.
      Intra-articular hylan G-F 20 (Synvisc) in the management of patellofemoral osteoarthritis of the knee (POAK).
      ,
      • Kamat Y.D.
      • Patel N.G.
      • Galea A.
      • Ware H.E.
      • Dowd G.S.E.
      Platelet-rich plasma injections for knee pathologies: a review.
      Hence their use could be reserved as a second line to other failed conservative treatment measures when surgical intervention is not on the cards or as an adjuvant to surgical techniques.

      4.2 Operative treatment

      With multiple options now available for operative intervention, the main determining factors are (a) age of the patient and (b) concomitant presence and severity of tibio-femoral wear.
      • Hinman R.S.
      • Crossley K.M.
      Patellofemoral joint osteoarthritis: an important subgroup of knee osteoarthritis.
      Kim et al. stress on detailed evaluation of dysplasia and localization of the cartilage lesion on the patella in younger patients with isolated patellofemoral degeneration.
      • Kim Y.-M.
      • Joo Y.-B.
      Patellofemoral osteoarthritis.
      In younger patients with early grade degeneration, reconstruction of the medial patellofemoral ligament with realignment of the distal insertion and/or reshaping of the trochlea (Trochleoplasty) is well established. For milder instability, arthroscopic procedures are also described with good success rates and earlier rehabilitation.
      • Naik A.
      • Shetty A.A.
      • Kim S.J.
      Patellar stabilization-Minimally invasive arthroscopic technique (Shetty & Kim).
      A working classification of procedures for patellofemoral degeneration can be proposed as the following:

      4.2.1 Procedures aimed at reducing pressure on the articular surface

      Lateral release of the lateral patellar retinaculum is amongst the commonest procedures undertaken arthroscopically for lateral tilt, tightness and resultant patellofemoral degeneration and pain.
      • Post W.R.
      Clinical evaluation of patients with patellofemoral disorders.
      Pain relief might be unpredictable and take quite some time during which patient counseling and cooperation with strengthening of the VMO is vital. It is done on it's own or in conjunction with other procedures under type (b) and (c) above. Open lateral release done with quadrantectomy of the lateral facet of patella has been reported to have better mid-to long-term results in established patellofemoral osteoarthritis.
      • Wetzels T.
      • Bellemans J.
      Patellofemoral osteoarthritis treated by partial lateral facetectomy: results at long-term follow up.
      Tibial tubercle osteotomy (TTO) is believed to reduce the load on a degenerate area of the patella and transfer to a less loaded area of the articular cartilage. It is described for patellar degeneration too but undertaken more commonly in younger patients, as a part of instability treatment.
      • Saleh K.J.
      • Arendt E.A.
      • Eldridge J.
      • Fulkerson J.P.
      • Minas T.
      • Mulhall K.J.
      Symposium. Operative treatment of patellofemoral arthritis.
      Prior to the undertaking of the above type of procedure, it is recommended to measure the indices as per MRI and CT as described in the earlier section. A high TT- TG distance would negate any beneficial effects of the procedures described above and necessitate concomitant TTO with medialization and anteriorisation. Table 1 provides an algorithm for the decision making process taking the above factors into account.
      Table 1Treatment algorithm for patello-femoral chondropathy.
      Table thumbnail fx1

      4.2.2 Correction of patellar instability

      Patellar instability surgery encompasses a wide range of options based on the patient's age, frequency of instability and underlying cause. Medial patella-femoral ligament (MPFL) ruptures comprise 3% of all knee injuries and its reconstruction is a recognized option for post traumatic dislocations.
      • Dall'Oca C.
      • Elena N.
      • Lunardelli E.
      • Ulgelmo M.
      • Magnan B.
      MPFL reconstruction: indications and results.
      Tibial tubercle transfer, trochleoplasty, tibial and femoral osteotomies to correct varus, valgus or rotational malalignment are additional procedures that can be used individually or in tandem.
      • Thompson P.
      • Metcalfe A.J.
      Current concepts in the surgical management of patellar instability.
      An example of this is the four in one procedure for recurrent dislocations.
      • Joo S.Y.
      • Park K.B.
      • Kim B.R.
      • Park H.W.
      • Kim H.W.
      The “four-in-one” procedure for habitual dislocation of the patella in children: early results in patients with severe generalised ligamentous laxity and aplasis of the trochlear groove.
      While success with all the above procedures has been documented, each of them have their individual appropriate indications as per the underlying pathology. While the soft tissue element is addressed best with MPFL reconstruction, distal procedures may be concomitantly required with high TT-TG distance. Trochleoplasty on the other hand can be done independently and works well in the presence of trochlear dysplasia. It has a limited place once degenerative chondropathy has set in the lateral facet of the patella as the pressure in that compartment of the joint would be increased.
      Further discussion on instability has been limited as this is intended to be a review of treatment for degenerative pathologies.

      4.2.3 Cartilage regeneration

      Regeneration of hyaline cartilage has come a long way from osteo-articular autograft and allograft transfer (OATS), two-stage open autologous chondrocyte implantation (ACI) to arthroscopic to single stage mesenchymal cell induced chondrogenesis and artificial collagen induced chondrogenesis.
      • Shetty A.A.
      • Kim S.J.
      • Shetty V.
      • Jang J.D.
      • Huh S.W.
      • Lee D.H.
      Autologous collagen induced chondrogenesis (ACIC: shetty-Kim technique) - a matrix based acellular single stage arthroscopic cartilage repair technique.
      ,
      • Huh S.W.
      • Shetty A.A.
      • Ahmed S.
      • Lee D.H.
      • Kim S.J.
      Autologous bone-marrow mesenchymal cell induced chondrogenesis (MCIC).
      • Nho S.J.
      • Foo L.F.
      • Green D.M.
      • et al.
      Magnetic resonance imaging and clinical evaluation of patellar resurfacing with press-fit osteochondral autograft plugs.
      • Peterson L.
      • Minas T.
      • Brittberg M.
      • Nilsson A.
      • Sjögren-Jansson E.
      • Lindahl A.
      Two- to 9-year outcome after autologous chondrocyte transplantation of the knee.
      • Torga Spak R.
      • Teitge R.A.
      Fresh osteochondral allografts for patellofemoral arthritis: long-term followup.
      Marrow stimulation procedures still have a place in smaller defects and are still the commonest employed technique under this type of intervention.
      • Mithoefer K.
      • McAdams T.
      • Williams R.J.
      • Kreuz P.C.
      • Mandelbaum B.R.
      Clinical efficacy of the microfracture technique for articular cartilage repair in the knee: an evidence-based systematic analysis.
      Lateral facet or inferior pole cartilage lesions seem to do better with regeneration techniques as opposed to superior pole, medial facet or generalized pathology. Similarly cartilage regeneration procedures fare better when combined with a type (a) procedure above i.e. release of tight structure or osteotomy.

      4.2.4 Surface replacement

      Though replacement procedures have reported the best long-term outcomes for established osteoarthritis, they are salvage procedures and to be reserved for the older age group. Selective patellofemoral replacement can now be reliably advocated for disease limited within the compartment with newer generation prostheses and perform much better in the younger individual as compared to earlier described salvage procedures like patellectomy.
      • Mosier B.A.
      • Arendt E.A.
      • Dahm D.L.
      • Dejour D.
      • Gomoll A.H.
      Management of patellofemoral arthritis: from cartilage restoration to arthroplasty.
      In elderly patients, total knee arthroplasty (TKA) produces superior results than patellofemoral replacement.
      • Laskin R.S.
      • van Steijn M.
      Total knee replacement for patients with patellofemoral arthritis.
      Resurfacing of the patella during the TKA should be undertaken, particularly when the main symptom component of the tricompartmental osteoarthritis is anterior knee pain.

      5. Conclusion

      Patellofemoral degeneration can overall be considered as the single most prevalent of knee pathologies across all ages. Management requires a detailed clinical assessment of associated factors and of involvement of the other knee compartments. Careful decision making of treatment options must be undertaken with detailed counseling, as success rates are lesser than that of tibio-femoral arthritis.

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