Aim. Nail patella syndrome (NPS) is a skeletal dysplasia with patellofemoral dysfunction as a key symptom. We present the first in-depth radiological evaluation of the knee in a large series of NPS patients and describe the typical malformations. Patients and Methods. Conventional radiological examination of 95 skeletally mature patients with NPS was performed. Patellar morphology was classified according to the Wiberg classification as modified by Baumgartl and Ficat criteria, and trochlear shape was classified according to the Dejour classification. Results. Patellar aplasia was present in 4/90 (4%), and patellar hypoplasia in 77/90 (86%) of patients. The prevailing patellar shapes were type III, type IV and Hunter’s cap. No patellar shape genotype-phenotype association could be found. The malformations of the distal femur comprised shortening of the lateral femoral condyle in 46 out of 84 patients (55%), with a prominent anterior surface of the lateral femoral condyle in 47 out of 84 patients (56%) and a flat anterior surface of the medial femoral condyle in 78 out of 85 patients (92%). The trochlea was type A1 according to the Dejour classification in 79 out of 85 patients (93%). . Conclusion. An easily recognisable characteristic quartet of malformations consisting of patellar aplasiaor hypoplasia and the malformations of the distal femur was found in 22 out of 81 patients (27%), with the majority displaying at least three malformations. Take home message: The distinct malformations of the knee in nail patella syndrome are easily recognisable on conventional radiographs and lead to the correct interpretation of the aberrant morphology which is essential in the treatment of these patellofemoral disorders. Cite this article: Bone Joint J 2016;98-B:483–9

We retrospectively analysed the MR scans of 25 patients with patellofemoral dysplasia and ten control subjects, to assess whether there was any change in the morphology of the patella along its vertical length. Ratios were calculated comparing the size of the cartilaginous and subchondral osseous surfaces of the lateral and medial facets. We also classified the morphology using the scoring systems of Baumgartl and Wiberg. There were 18 females and seven males with a mean age of 20.2 years (10 to 29) with dysplasia and two females and eight males with a mean age of 20.4 years (10 to 29) in the control group. In the patient group there was a significant difference in morphology from proximal to distal for the cartilaginous (Analysis of variance (ANOVA) p = 0.004) and subchondral osseous surfaces (ANOVA, p = 0.002). In the control group there was no significant difference for either the cartilaginous (ANOVA, p = 0.391) or the subchondral osseous surface (ANOVA, p = 0.526). Our study has shown that in the dysplastic patellofemoral articulation the medial facet of the patella becomes smaller in relation to the lateral facet from proximal to distal. MRI is needed to define clearly the cartilaginous and osseous morphology of the patella before surgery is considered for patients with patellofemoral dysplasia

The purpose of this study was to test the hypothesis that patella alta leads to a less favourable situation in terms of patellofemoral contact force, contact area and contact pressure than the normal patellar position, and thereby gives rise to anterior knee pain. A dynamic knee simulator system based on the Oxford rig and allowing six degrees of freedom was adapted in order to simulate and record the dynamic loads during a knee squat from 30° to 120° flexion under physiological conditions. Five different configurations were studied, with variable predetermined patellar heights. The patellofemoral contact force increased with increasing knee flexion until contact occurred between the quadriceps tendon and the femoral trochlea, inducing load sharing. Patella alta caused a delay of this contact until deeper flexion. As a consequence, the maximal patellofemoral contact force and contact pressure increased significantly with increasing patellar height (p < 0.01). Patella alta was associated with the highest maximal patellofemoral contact force and contact pressure. When averaged across all flexion angles, a normal patellar position was associated with the lowest contact pressures. Our results indicate that there is a biomechanical reason for anterior knee pain in patients with patella alta

We describe our experience with the ‘four-in-one’ procedure for habitual dislocation of the patella in five children (six knees). All the patients presented with severe generalised ligamentous laxity and aplasia of the trochlear groove. All had a lateral release, proximal ‘tube’ realignment of the patella, semitendinosus tenodesis and transfer of the patellar tendon. The mean age at the time of the operation was 6.1 years (4.9 to 6.9), and the patients were followed up for a mean of 54.5 months (31 to 66). The clinical results were evaluated using the Kujala score. There has been no recurrence of dislocation. All the patients have returned to full activities and the parents and children were satisfied with the clinical results. The mean Kujala score was 95.3 (88 to 98). Two patients had marginal skin necrosis which healed after debridement and secondary closure. These early results in this small group have shown that the ‘four-in-one’ procedure is effective in the treatment of obligatory dislocation of the patella in children with severe ligamentous laxity and trochlear aplasia

We used three-dimensional movement analysis by computer modelling of knee flexion from 0° to 50° in 14 knees in 12 patients with recurrent patellar dislocation and in 15 knees in ten normal control subjects to compare the in vivo three-dimensional movement of the patella. Flexion, tilt and spin of the patella were described in terms of rotation angles from 0°. The location of the patella and the tibial tubercle were evaluated using parameters expressed as percentage patellar shift and percentage tubercle shift. Patellar inclination to the femur was also measured and patellofemoral contact was qualitatively and quantitatively analysed. The patients had greater values of spin from 20° to 50°, while there were no statistically significant differences in flexion and tilt. The patients also had greater percentage patellar shift from 0° to 50°, percentage tubercle shift at 0° and 10° and patellar inclination from 0° to 50° with a smaller oval-shaped contact area from 20° to 50° moving downwards on the lateral facet. Patellar movement analysis using a three-dimensional computer model is useful to clearly demonstrate differences between patients with recurrent dislocation of the patella and normal control subjects

Patella infera can cause knee pain and lead to patellofemoral osteoarthritis. Treatment is usually unsatisfactory. We describe a case of severe patella infera after operative treatment for fracture of the patella. We used Ilizarov external fixation and gradual lengthening of the patellar tendon. The patellar height was restored and the patient’s symptoms were much improved

1. Two cases of haemangioma of the patella are reported. 2. In one case pain alone brought the patient for treatment; in the other, a pathological fracture was the first symptom. 3. In neither case was a firm diagnosis made before excision and histological examination of the patella. 4. In each case a good result followed removal of the patella: this is probably the best method of treatment. 5. The literature relating to haemangioma of bone and to tumours of the patella is briefly reviewed

Aims

The aim of this study was to establish consensus statements on medial patellofemoral ligament (MPFL) reconstruction, anteromedialization tibial tubercle osteotomy, trochleoplasty, and rehabilitation and return to sporting activity in patients with patellar instability, using the modified Delphi process.

We carried out three total knee replacements with proximal realignment in two patients with severe osteoarthritis of the knee and congenital dislocation of the patella. During the operation, the femur and the tibia were cut according to the recommendations of the manufacturer of the implant. The femoral component was placed in external rotation and the centre of the tibial component aligned in relation to the tibial tuberosity with regard to rotation and translation. After making the bone cuts, the iliotibial tract was detached from Gerdy’s tubercle, the popliteus tendon divided, and the biceps femoris tendon elongated by Z-plasty. After the trial implants were positioned, a proximal re-alignment procedure was performed. One knee had deep infection. There was one dislocated patella which was repositioned, and walking ability was improved in all knees. We believe that the rotational alignment of a prosthesis is as important as the soft-tissue surgery

Aims

This study aimed to describe the use of revision knee arthroplasty in Australia and examine changes in lifetime risk over a decade.

We retrospectively reviewed the operative treatment carried out between 1988 and 1994 of eight patients with habitual patellar dislocation. In four the condition was bilateral. All patients had recurrent dislocation with severe functional disability. The surgical technique involved distal advancement of the patella by complete mobilisation of the patellar tendon, lateral release and advancement of vastus medialis obliquus. The long-term results were assessed radiologically, clinically and functionally using the Lysholm knee score, by an independent observer. The mean age at operation was 10.3 years (7 to 14) with a mean follow-up of 13.5 years (11 to 16). One patient required revision. At the latest follow-up, all patellae were stable and knees functional with a mean Lysholm knee score of 98 points (95 to 100). In those aged younger than ten years at operation there was a statistically significant improvement in the sulcus angle at the latest follow-up (Student’s t-test, p = 0.001). Two patients developed asymptomatic patella infera as a late complication. This technique offers a satisfactory treatment for the immature patient presenting with habitual patellar dislocation associated with patella alta. If performed early, we believe that remodelling of the shallow trochlea may occur, adding intrinsic patellofemoral stability

The Insall-Salvati method of determining the position of the patella by radiography was employed in fifty-one patients with chondromalacia patellae that had been proved at arthrotomy. There was no definite relationship between chondromalacia patellae and patella alta. There was, however, a highly significant statistical difference between the ratio of the length of the patella to that of the patellar tendon in normal men and women

1. A series of 196 fractures of the patella has been reviewed. 2. The treatment adopted was excision of the whole bone—l0l; excision of part of the bone—33; open reduction and suture—18; suture with later excision—14; no operation—30. 3. The average time of post-operative disability varied from 3·6 to 5·3 months. The time was appreciably less when operation was carried out before the fourteenth day than when it was done later. 4. An attempt was made to follow up, two to five years after injury, those patients in whom the result was not influenced by other major injuries of the limbs or by unexpected complications. Replies to questionnaires were received from 116 patients. 5. Of these, all regained a good range of movement, varying from 90 degrees of flexion to full movement, whether treatment was by excision of part or all the bone, or by open reduction and suture. 6. The late results of excision of the patella, as estimated by the patients themselves two to five years after treatment, showed that there was considerable residual disability. 7. After total excision of the bone only 5 per cent. of patients considered that the knee was normal; 90 per cent. complained of aching; 60 per cent. complained of "giving way." After excision of one fragment, about half the patients regarded the knee as normal and half complained of aching and stiffness. 8. The number of fractures in this series treated by accurate internal fixation was too small to make justifiable comparisons. 9. The indications for non-operative treatment, open reduction and accurate internal fixation, excision of one fragment, and excision of the whole bone are discussed. 10. Excision of part or all the patella is often inevitable, but some claims made in the past for the results of this operation are not substantiated

An inquiry was made of ninety-seven patients with recurrent dislocation of the patella and forty patients with recurrent dislocation of the shoulder to see how often they had a relative similarly affected, and also how often such dislocation is associated with, and perhaps caused by, familial joint laxity. Ten of those with recurrent dislocation of the patella and two of those with recurrent dislocation of the shoulder were found to have a near relative with a similar dislocation. Familial joint laxity was found in two of the ten families with more than one member affected by recurrent patellar dislocation, and in both those with more than one member with recurrent dislocation of the shoulder. Familial joint laxity was also found in two out of twenty patients with recurrent dislocation of the patella who had no family history of similar dislocation; but in none out of twenty patients with recurrent dislocation of the shoulder and who had no family history of similar dislocation. Familial joint laxity may be the only cause of recurrent dislocation of the shoulder occurring in more than one member of the family. But there are other, as yet undefined, causes of familial recurrent dislocation of the patella

1. Seventy-seven operations on the patella have been reviewed. 2. There is no evidence that arthritic changes in the femoral condyles are an inevitable sequel of complete excision of the patella. 3. There is a direct relationship between the severity of symptoms after complete excision of the patella and the extent of ossification in the quadriceps tendon. 4. Patello-femoral arthritis after partial excision of the patella may be due to faulty realignment of the patellar ligament and consequent tilting of the patellar remnant towards the femoral condyles

Osteochondral fractures of the patella should be recognised early, loose bodies removed, and defects in the articular surfaces smoothed off, or the patella removed if it is extensively involved. Plication of the capsule on the medial side is recommended in order to prevent recurrence of the injury and to prevent dislocation of the quadriceps tendon. in cases where the patella is removed

An electromyographic investigation of patients with subluxation of the patella has been carried out on the parts of the extensor apparatus which actively contribute to the alignment of the patella, both before and after the operation to correct this disorder. The electromyographic pictures have revealed a sharp fall in the activity of the vastus medialis, with full recovery to normal values after a corrective operation. Even if the aligning function of the patella is altered by a variety of factors, the present study confirms the importance of the vastus medialis in the pathogenesis of malalignment of the extensor mechanism

We reviewed 13 cases of osteochondritis dissecans of the patella followed-up for 18 months to 19 years. Two were treated conservatively with excellent results, and 11 by operation with six excellent, four good and one fair result. There was complete radiographic healing of the defect in 10 cases and partial healing in three. The size of the osteochondritic lesion appeared to be of prognostic significance. Osteochondritis dissecans of the patella is the result of repeated minor injuries to the articular surface. Operation is indicated for persistent pain, intra-articular loose bodies and subchondral sclerosis; excision of the fragment and curettage of the crater, with or without drilling, is recommended

1. A study has been made of the blood supply of the human patella. There are two main systems, one penetrating the middle third of the anterior surface and the other entering the lower pole of the bone behind the patellar ligament. 2. The relationship between these findings and the complication of avascular necrosis of the upper fragment of the patella after fracture is discussed. Forty-one cases of necrosis after operation have been studied and notes made on the pathological, clinical and radiological evolution of the condition. Whatever the severity of the ischaemic necrosis the prognosis was not substantially affected and good function was observed in all knees six months after injury. 3. The surgical implications of the vascular anatomy are discussed. It is pointed out that surgical intervention may damage the blood vessels entering the anterior surface of the bone and that circumferential repair of patellar fractures may strangle the vessels in their peripatellar course. 4. If removal of one-half of the patella after a transverse fracture is indicated, vascular studies indicate that the upper fragment should be removed

1. Chondromalacia, sometimes a precursor of osteoarthritis, is present in the articular cartilage of the patella of most people by the age of thirty; it causes symptoms in only a few, and it gives rise to osteoarthritis in fewer still. It may progress slowly or quickly but there is no clinical method of assessing the prognosis at an early stage. 2. The earliest change is swelling of the cartilage associated with a decrease in the chondroitin sulphuric acid content of the matrix. Later the cartilage fissures and flakes off to expose the bone, and there are reactive changes in the cartilage, bone and synovial membrane. The process is described and the etiology discussed. 3. The symptoms, signs and treatment are discussed. Operation, which has been performed only when there are disabling symptoms, may consist in removing part or the whole of the articular cartilage, or in excision of the patella. The results in forty-six knees are given

We investigated the three-dimensional morphological differences of the articular surface of the femoral trochlea in patients with recurrent dislocation of the patella and a normal control group using three-dimensional computer models. There were 12 patients (12 knees) and ten control subjects (ten knees). Three-dimensional computer models of the femur, including the articular cartilage, were created. Evaluation was performed on the shape of the articular surface, focused on its convexity, and the proximal and mediolateral distribution of the articular cartilage of the femoral trochlea. The extent of any convexity, and the proximal distribution of the articular cartilage, expressed as the height, were shown by the angles about the transepicondylar axis. The mediolateral distribution of the articular cartilage was assessed by the location of the medial and lateral borders of the articular cartilage. The mean extent of convexity was 24.9° . sd. 6.7° for patients and 11.9° . sd. 3.6° for the control group (p < 0.001). The mean height of the articular cartilage was 91.3° . sd. 8.3° for the patients and 83.3° . sd. 7.7° for the control group (p = 0.03), suggesting a wider convex trochlea in the patients with recurrent dislocation of the patella caused by the proximally-extended convex area. The lateral border of the articular cartilage of the trochlea in the patients was more laterally located than in the control group. Our findings therefore quantitatively demonstrated differences in the shape and distribution of the articular cartilage on the femoral trochlea between patients with dislocation of the patella and normal subjects

1. Attention is drawn to the importance of taking tangential radiographs of the patella in all cases of injury to the knee, especially when there is difficulty in distinguishing between recurrent dislocation of the patella and tear of a meniscus. 2. New bone formation along the medial side of the patella confirms a diagnosis of recurrent dislocation. 3. The importance of Coleman's original observations is stressed

The results of resurfacing or not resurfacing the articular cartilage of the patella were reviewed in 71 knees--47 with rheumatoid arthritis and 24 with osteoarthritis--which had been replaced with the ICLH prosthesis. Two rheumatoid and osteoporotic patellae developed transverse fractures with separation and were excluded from the review. The results showed that resurfacing the patella greatly reduced peripatellar pain with no counter-balancing disadvantage

A case of duplication of the patella in the coronal plane is reported. Previously reported cases of double patella have shown sagittal or vertical duplication, and some have been associated with multiple epiphyseal dysplasia. In our case, excision of one patella and realignment of the extensor mechanism relieved symptoms of giving-way

Lateral instability of the patella was found after recurrent, habitual and permanent dislocations. Contracture of soft tissues lateral to the patella only occurred with habitual and permanent dislocations, but medial laxity was present in all cases. After adequate release of the lateral contracture, the medial stability was improved by transposition of the lower three-quarters of the pes anserinus to the medial border of the patella, and the patellar ligament. This created a relatively unstretchable physiological sling which ensured dynamic stability of the patella. Six recurrent, 21 habitual and nine permanent dislocations of the patella were treated by this method. Results were excellent in 21 patients, good in 13 and fair in two. The follow-up period varied from 21 to 84 months. There have been no recurrences to date

Comminuted and displaced fractures of the inferior pole of the patella are not easy to reduce and it is difficult to fix the fragments soundly enough to allow early movement of the knee. We have evaluated the clinical effectiveness of the separate vertical wiring technique in acute comminuted fractures of the inferior pole of the patella. A biomechanical study was also performed using ten pairs of embalmed cadaver knees. A four-part fracture was made on the inferior pole of the patella and fixed by two separate vertical wires on one side and two pull-out sutures after partial patellectomy on the other. The ultimate load to failure in the first group was significantly higher than in the second (250.1± 109.7 N v 69.7 ± 18.9 N, p< 0.002), as was the stiffness (279.9 ± 76.4 N/mm v 23.2 ± 11.4 N/mm, p< 0.001). The separate wire technique was used in 25 patients with comminuted fractures of the inferior pole of the patella who were followed up for a mean period of 22 months (10 to 50). All the fractures healed at a mean of seven weeks (6 to 10). No breakage of a wire or infection occurred. The mean grading at the final follow-up was 29.5 points (27 to 30) using the Böstman method. This technique preserved the length of the patella, fixed the comminuted fragments of the inferior pole and avoided long-term immobilisation of the knee

Between 1989 and 1993 we implanted a matrix support prosthesis made of carbon fibre for the treatment of chronic painful articular defects of the patella in 27 patients. The mean period of follow-up was 33 months (11 to 54) with clinical and arthroscopic evaluation of the implant. Overall, there were four excellent, three good, seven fair and 13 poor results. Nine patients subsequently had a patellectomy for persistent pain at a mean of 27 months after surgery (14 to 47). The mean visual analogue pain scores in those who retained their patella were 7.6 before operation and 5.5 at the time of the latest follow-up. Patient satisfaction for the entire group was 41%. There appeared to be good incorporation of the prosthesis and a satisfactory ingrowth of fibrocartilage, but the poor results in 48% and low patient satisfaction discourage us from recommending the procedure for lesions of the articular cartilage of the patella. The consistent seeding of the joint with carbon-fibre debris and a histiocytic giant-cell reaction in the synovium are also a cause for concern

We reviewed 41 knees after arthroscopic lateral release for recurrent dislocation of the patella at a mean follow-up of four years, and graded the results according to the criteria of Crosby and Insall (1976). There were no dislocations after operation in 28 knees (68%); the less satisfactory results were in patients with subluxation of the patella on extension of the knee and those with generalised ligamentous laxity. There were no complications. A characteristic and previously unreported lesion of the patellar surface was seen in eight of the 41 knees. The results of lateral release are better than those reported for other techniques. This treatment, by either open or arthroscopic methods, is recommended

The family we record draws attention to an association between recurrent dislocation of the patella and joint laxity, which is not confined to the knee. This may pass unrecognised if specific inquiry is not made. In this and other families reported, the joint laxity is inherited, as though due to a dominant gene, but some only of those affected suffer recurrent dislocation of the patella. It is probable that there are other genetically determined causes of recurrent patellar dislocation. In three other families we have seen more than one subject of patellar dislocation, but none had lax ligaments, and two other families have been recorded with no mention of associated joint laxity

We investigated the clinical outcome of a reconstructive procedure of the medial patellofemoral ligament for the treatment of habitual or recurrent dislocation of the patella in four children (6 knees), with a minimum follow-up of four years. The technique involves transfer of the tendon of semitendinosus to the patella using the posterior one-third of the femoral insertion of the medial collateral ligament as a pulley. There was no recurrence of dislocation after surgery. The mean Kujala score at follow-up was 96.3 points. Radiological assessment showed that the congruence angle, the tilt angle and the lateral shift radio were restored to normal. The lateral and medial stress shift ratios and the Insall-Salvati ratio remained abnormal. We conclude that this technique can be recommended for the treatment of habitual or recurrent patellar dislocation in children, although hypermobility and patella alta are not fully corrected

Eighteen patients with acute dislocation of the patella had associated osteochondral fractures. This fracture complicates approximately 5% of all acute dislocations of the patella occurring in children. Three types of fracture patterns were noted. All patients who were treated by immediate arthrotomy and excision or replacement of the osteochondral fragment and repair of the acute dislocation of the patella made an uneventful recovery with no recurrence of the dislocation. In those patients in whom the osteochondral fragment was removed but with no repair the dislocation recurred

Out of a total of 623 patients who, over a ten-year period, underwent primary total knee replacement (TKR) without patellar resurfacing, 20 underwent secondary resurfacing for chronic anterior knee pain. They were evaluated pre- and postoperatively using the clinical and radiological American Knee Society score. The mean follow-up was 36.1 months (12 to 104). The mean knee score improved from 46.7 to 62.2 points and the mean functional score from 44.7 to 52.2 points. Only 44.4% of the patients, however, reported some improvement; the remainder reported no change or deterioration. The radiographic alignment of the TKR did not influence the outcome of secondary resurfacing of the patella. Complications were noted in six of the 20 patients including fracture and instability of the patella and loss of movement. Anterior knee pain after TKR remains difficult to manage. Secondary resurfacing of the patella is not advocated in all patients since it may increase patient dissatisfaction and hasten revision

This investigation has been performed to study the relationship between the articular surfaces of the patella and the femoral condyles with the knee extended. A computerised tomographic scanning technique was used on twelve normal subjects in whom it was shown that when the knee is in full extension the patella usually lies laterally and incongruently in contact with the lateral femoral condyle

The authors wished to determine the late results of the Hauser operation, with special reference to the development of osteoarthritis. Predisposing factors associated with recurrent dislocation of the patella were also investigated. Thirty-five patients with forty-our surgically treated knees attended for review, ten to twenty-fve (aerage sixteen) years after operation. Two patients had subsequently undergone excision of the patella. Ten patients gave a family history of recurrent dislocation of the patella and seven patients showed generalised joint laxity. Pain was present in eight knees before operation and was present in thirty-three knees (75 per cent) at the time of review. Patellar crepitus was present in thirty-seven out of forty-two knees (88 per cent) at review. Osteoarthritis was present in thirty out of forty-two knees (70 per cent). The incidence increases with time since operation and the present age of the patient. It is concluded that the Hauser operation prevents further dislocation but does not prevent the development of osteoarthritis. It is possible that a simple soft-tissue operation which effectively prevents dislocation might achieve the same results

1. Five new cases of pyogenic osteomyelitis of the patella are reported. 2. The clinical features are reviewed and the diagnostic pitfalls enumerated

The Blackburne and Peel method of assessing the position of the patella was applied to 185 knees with Osgood--Schlatter disease in 125 patients. The normal index of 0.80 was confirmed in 73 control knees. The average index in the knees with Osgood--Schlatter disease measured 1.01 (patella alta) boys and 0.91 in girls. The value increased to 1.06 in boys with radiological evidence of loose ossicles in the tibial tuberosity or the patellar tendon. This finding indicates that the strong pull of the well-developed quadriceps muscle is probably the most important aetiological factor in patella alta associated with Osgood--Schlatter disease

Removal of a small, moderate or major part of the articular cartilage of the patella for chondromalacia has been successful in twenty-two knees out of twenty-eight. These knees are functionally at least as good as after a successful patellectomy, and their appearance is better. Only one knee that was initially improved by operation deteriorated during a follow-up period of five to seven years. Of the six unsuccessful results, four were in patients whose symptoms began during adolescence. Excision of articular cartilage therefore seems to be contra-indicated during adolescence and when there is reason to believe that the chondromalacia will be rapidly progressive. Failure of excision of articular cartilage to relieve the symptoms within a few months is an indication for patellectomy

A case of intra-articular dislocation of the patella is reported. Its special interest lies in the apparent simplicity of both injury and reduction

Case histories are given of three patients, two of whom had stress fractures of the patella, and one had a similar condition due to stress

We report a prospective study of 55 patients with acute primary patellar dislocation, all treated by operation and followed up for at least two years. Diagnosis was based on the history of a lateral displacement, with medial tenderness and a positive apprehension test; redislocations were excluded. Before operation, the difference in lateral shift on skyline views of the injured and control patellae was highly significant. At operation, rupture of the medial retinaculum of the patella was seen in all but one case. There were medial marginal fractures of the patella in 23 cases. Subjective results of the operation were excellent or good in 44 of the 55 at two years with a redislocation rate of only 9%. Most patients were able to return to the same level of sporting activity as before the injury

1. A case of primary osteosarcoma of the patella is reported. 2. A brief review of the literature has been made. 3. In the author's opinion only nine genuine cases have been reported, including the present case

Resection arthroplasty of the patella has been found to be a satisfactory procedure for the treatment of patellofemoral pain caused by osteoarthritis. In the present series 60% of the operated cases were pain-free on a 31-month average follow-up. The patients found it easier to climb stairs and to kneel and in most cases the radiographic joint space was good

We present a case of superior dislocation of the patella trapped by interlocked osteophytes. Unlike previous reports, in which the mechanism resulted from a blow to the inferior pole, it is postulated that increased load on the extensor mechanism, combined with patella alta and patellofemoral osteophytes, caused locking of the knee in extension

1. A study has been made of the treatment of recurrent dislocation of the patella in 106 knees in seventy-six patients. 2. In young adults in whom degenerative changes in the knee were not severe at the time of operation transplant of the tibial tubercle gave the best results. 3. In older patients and in those in whom osteoarthritic changes were present in the knee transplant of the tibial tubercle was unsatisfactory, but patellectomy with rerouting of the quadriceps mechanism gave fair results. 4. Tibial tubercle transplant is contra-indicated in children because it may give a recurvatum deformity. 5. When the dislocation is permanent, operation may be unnecessary, but if it becomes inevitable simple patellectomy is the best procedure. 6. The results of plastic operations on the quadriceps expansion and of supracondylar femoral osteotomy are bad. 7. No operation can give consistently good results because the knee is usually congenitally weak, often as part of generalised ligamentous laxity

Patellectomy is at present the best operation for recurrent dislocation, not only because the immediate result is excellent, but because it avoids the later arthritis which must inevitably arise if a patella so damaged is retained

The Unified Classification System (UCS) was introduced because of a growing need to have a standardised universal classification system of periprosthetic fractures. It combines and simplifies many existing classification systems, and can be applied to any fracture around any partial or total joint replacement occurring during or after operation. Our goal was to assess the inter- and intra-observer reliability of the UCS in association with knee replacement when classifying fractures affecting one or more of the femur, tibia or patella. We used an international panel of ten orthopaedic surgeons with subspecialty fellowship training and expertise in adult hip and knee reconstruction (‘experts’) and ten residents of orthopaedic surgery in the last two years of training (‘pre-experts’). They each received 15 radiographs for evaluation. After six weeks they evaluated the same radiographs again but in a different order. . The reliability was assessed using the Kappa and weighted Kappa values. The Kappa values for inter-observer reliability for the experts and the pre-experts were 0.741 (95% confidence interval (CI) 0.707 to 0.774) and 0.765 (95% CI 0.733 to 0.797), respectively. The weighted Kappa values for intra-observer reliability for the experts and pre-experts were 0.898 (95% CI 0.846 to 0.950) and 0.878 (95% CI 0.815 to 0.942) respectively. The UCS has substantial inter-observer reliability and ‘near perfect’ intra-observer reliability when used for periprosthetic fractures in association with knee replacement in the hands of experienced and inexperienced users. Cite this article: Bone Joint J 2014;96-B:1669–73

1. Four cases of congenital lateral dislocation of the patella are described. 2. The significance of the associated flexion contracture is emphasised. 3. Early diagnosis and operative realignment of the extensor mechanism is considered to be important because it should avoid the secondary growth changes which can produce serious disability

Thirty-five patients with habitual dislocation of the patella in flexion were reviewed; eight were bilaterally affected. Each had undergone quadricepsplasty with an average follow-up of 6 years 9 months. Bands or contractures, most commonly in vastus lateralis, the iliotibial tract and rectus femoris were seen in each. Redislocation was seen in 12 knees. At review, 79% of the knees were normal. Quadriceps lengthening is an essential part of treatment and must be performed proximally. Causes for failure include reformation of contractures and failure to correct the initial abnormality fully

The role of muscle function in the aetiology of recurrent dislocation of the patella has been examined. Eleven of the 12 patients we studied had joint hypermobility. Muscle biopsies from eight of nine patients treated by surgery had a predominance of abnormal Type 2C fibres, and three of six patients whose quadriceps muscles were studied by electromyography also had abnormal results. Our preliminary findings suggest that there may be a primary muscular defect in many cases of recurrent dislocation of the patella

Six boys with fragmentation of the proximal pole of the patella are reported; the condition was bilateral in one. Four of the six presented with symptoms of Osgood-Schlatter's disease or Larsen-Johansson disease of the same or of the contralateral knee, but they had no symptoms or signs relating to the proximal pole of the patella; one also had features suggesting minimal chondromalacia patellae. Two boys had no objective abnormality in either knee. It is suggested that the fragmentation may be a further form of traction osteochondritis of the attachments of the quadriceps mechanism. Attention is drawn to its characteristic radiographic appearance, its association with other forms of juvenile traction osteochondritis (which are commonly symptomatic), and to its occurrence in boys aged 10 or 11 years