Purpose of Study: To further study a group of patients with characteristic features presenting with significant, perisistent, and seemingly hard to diagnose and so treat, knee pain.

Methods/Results: 16 cases were collected. The was no association with age. 8 cases were sent as a second opinion.

Causation: 7 cases:direct trauma [5: associated with MCL tears (1 chronic overload from triple-jump),1:a blow to front of knee, 1:chronic from kneeling]

In all cases the time to make the diagnosis was prolonged. All had pain, which on close questioning was ‘neuritic’ [burning] in approximately 2/3. It was exceedingly well localized in all. Altered sensation in the appropriate distribution was noted by the patient in 3 cases, but shown in 5 cases on examination. A positive Tinel test was present in all cases.

In approximately half of cases ultrasound plus diagnostic injection of local anaesthetic [+/− steroid] was useful. However 15 of the 16 came to surgery in which a neurolysis or removal of neuroma, in 3 cases, [all confirmed on histology] was undertaken plus the underlying causative factor dealt with eg excision of osteophyte or scar. One case settled [90% better according to patient] after ultrasound-guided injection of a prepatellar bursa which was irritating the infrapatellar branch of the nerve. Of the 15 who had had surgery 12 had complete resolution of symptoms.

Conclusion: Although a relatively uncommon this scenario is worth considering as a cause of significant morbidity, with a good outcome from treatment in most cases. The presentation is of persistent very well localized troubling pain with marked tenderness, and a positive Tinel test.

Purpose: The relationship of pattern of injury to this region of the knee to the intraoperative finding of abnormal common peroneal nerve position and associated nerve palsy was studied.

Methods: 54 consecutive patients with posterolateral corner disruption requiring surgery were assessed prospectively by MRI, arthroscopic examination, and by operative display. The pattern of disruption, the status of the biceps tendon and any displacement of the common peroneal nerve were recorded.

Results: Of the 54 cases, there were 9 with CPN palsy, 18 were seen to have distal injuries (13 suffering a fibular head avulsion fracture and 5 biceps tendon avulsion with no fracture). There was a strong relationship (p< 0.001) between such distal posterolateral corner injury and abnormal position of the common peroneal nerve, as 16 of the 18 (90%) patients were seen to have abnormal nerve position. No proximal injury resulted in abnormal nerve position and only 1 was associated with CPN palsy. 7 of the 13 cases of fibular head fracture had CPN palsy, and 1 of the 5 distal soft tissue avulsions.

Conclusion: There is a strong association of distal soft tissue avulsion and fibular head fracture and CPN palsy in these injuries. Whenever such a distal injury is suspected, the surgeon operating in this region should expect an abnormal position of the common peroneal nerve and appreciate the increased risk of iatrogenic damage. Presumably since the CPN is intimately bound to the biceps tendon by deep fascia, proximal retraction of the biceps tendon results in displacement of the CPN to an abnormal position and accounts for the high incidence of nerve palsy.

Introduction and Aims: To assess the tibiofemoral kinematics of the PCL deficient knee using vertical open-access ‘dynamic’ MRI.

Method: Tibiofemoral motion was assessed using open-access MRI, weight-bearing in a squat, through the arc of flexion from zero to 90 degrees in six patients with isolated rupture of the PCL in one knee [diagnosed from conventional MRI scanning and clinical assessment] and a normal contralateral knee. Mid-medial and mid-lateral sagittal images were analysed in all chosen positions of flexion in both knees to assess the relative tibiofemoral relationships. Passive sagittal laxity was assessed by performing the posterior and anterior drawer tests, while the knees were scanned, again using the same MRI scanner. The tibiofemoral positions during this stress MRI examination was measured from mid-medial and mid-lateral sagittal images of the knees.

Results: Rupture of the PCL leads to an increase in passive sagittal laxity in the medial compartment of the knee [P< 0.006]. In the weight-bearing scans, PCL rupture alters the kinematics of the knee with persistent posterior subluxation of the medial tibia so that the femoral condyle rides up the anterior upslope of the medial tibial plateau. This ‘fixed’ subluxation was observed throughout the extension-flexion arc being statistically significant at all flexion angles (P< 0.018 at 0°, P< 0.013 at 20°, P< 0.014 at 45°, P< 0.004 at 90°). The kinematics of the lateral compartment were not altered by PCL rupture to a statistically significant degree. The posterior drawer test showed increased laxity in the medial compartment.

Conclusion: PCL rupture alters the kinematics of the medial compartment of the knee resulting in ‘fixed’ anterior subluxation of the medial femoral condyle [posterior subluxation of the medial tibial condyle]. This study helps to explain the observation of increased incidence of osteoarthritis in the medial compartment and specifically femoral condyle, in PCL deficient knees.

Purpose: To assess if ACL reconstruction restores normal knee kinematics.

Methods: Tibiofemoral motion was assessed weight-bearing through the arc of flexion from 0 to 90° in ten patients who were at least 6 months following successful hamstring graft ACL reconstruction. Lachman’s test was also performed using dynamic MRI. Mid-medial and mid-lateral images were analysed in all positions to assess the tibiofemoral relationship.

Results: The laxity of the reconstructed knees was reduced to within normal limits. However the normal tibiofemoral relationship was not restored after ACL reconstruction with persistent anterior subluxation of the lateral tibial plateau throughout the arc of flexion 0–90°(p< 0.001).

Conclusion: Successful ACL reconstruction reduces joint laxity and improves stability but it does not restore normal knee kinematics.

Studies comparing the biomechanical properties of different meniscal repair systems are limited, and most have simply investigated load to failure. Meniscal tissue is highly anisotropic, and far weaker under tension in the radial direction. Loading to failure using high radially orientated loads may, therefore, not be the most physiologically relevant in-vitro test for repair of circumferential tears, and determining increases in gapping across repair sites under cyclical loading at lower loads may be of greater importance. This study aimed to determine the load to failure for 4 different meniscal repair techniques, and to assess gapping across repairs under cyclical loading.

Bovine menisci were divided vertically, 5mm from the peripheral edge to simulate a circumferential tear, and then repaired using 1 of 4 techniques: vertical loop sutures using 2-0 PDS, bioabsorbable Meniscal Arrows (Atlantech), T-Fix Suture Bars (Acufex) or Meniscal Fasteners (Mitek). 9 specimens were tested in each group using an Instron 5565 materials testing machine with Merlin control software to determine load to failure. A further 9 specimens in each group were tested by cyclical loading between 5N and 10N at 20mm/min for 25 cycles. Gapping across the repairs under cyclical loading was measured using a digital micrometer and a Differential Voltage Reluctance Transducer.

The peak load to failure values for each repair method did not appear to fit a Gaussian distribution, but were skewed to the left due to some samples failing at lower loads than the main cluster. Results were analysed using the Kruskal-Wallis test, with Dunn’s multiple comparison post test. The results for gapping across the repairs from the cyclical testing all appeared to fit the Gaussian distribution, and these were analysed by Analysis of Variance, with Tukey’s multiple comparison post test. All analysis was performed using Prism (Graph-pad) Software.

The mean loads to failure for each of the repair groups were: Sutures 72.7 N, T-Fix 49.1 N, Fasteners 40.8 N, and Arrows 34.2 N. The load to failure was significantly greater with the Suture group compared to the Arrows (p< 0.01) or the Fasteners (p< 0.05). The mean gapping across the repairs for each of the repair groups after 25 loading cycles were: Sutures 3.29mm, Arrows 2.18mm,Fasteners 3.99mm,andT-Fix 3.47mm.The mean gapping was significantly less for the Arrows compared to the Sutures (p< 0.05), the Fasteners (p< 0.01), or the T-Fix (p< 0.05).

The results confirm that meniscal repair by suturing gives the highest load to failure, but show that Arrows give superior hold under lower loads, with the least gapping across repairs under cyclical loading by this testing protocol.