The ankle is one of the commonest sites of injury. Calculations from Scandinavian figures suggest an incidence of ankle sprains in East Lancashire of about 2000/year. Munk et al found that, 10 years after an ankle sprain, 20% had instability and 5% had persistent pain.
The complaint of giving way of the ankle is called “functional instability” (this is not a judgemental term regarding the genuineness or otherwise of the complaint). “Mechanical instability” is an abnormal amount of displacement of the talus with respect to the tibia on stress testing. Most series suggest that one is often present without the other, and in particular that many patients with functional instability do not have mechanically unstable ankles. A variety of functional abnormalities have been described, such as proprioceptive deficits, reflex abnormalities and abnormal muscle control. In addition, impingement, loose bodies and arthritis can produce a feeling of instability. A few patients may have instability of the subtalar, calcaneocuboid or lesser tarsal joints, and there is a strong association with peroneal tendon tears and instability.
Impingement
Impingement is pain due to soft tissue being “nipped” between moving joint components, In the ankle it may occur either anteriorly or posteriorly. The commonest site is the anterolateral joint line and lateral corner, with post-traumatic synovitis and/or damage to the tibiofibular syndesmosis. Some patients, often sports players, develop bony spurs on the tibia and talus which nip the anterior joint capsule.
Posterior impingement may be associated with posterior ankle and/or subtalar synovitis, a prominent posterior talar tubercle or os trigonum, or flexor hallucis longus tendonopathy.
Osteochondritis dissecans (OCD)
The talus is one of the common sites of OCD, in which cartilage and/or underlying bone defects form, sometimes with cysts in the bone or detachment of joint surface to form loose bodies. About 10% of talar lesions have opposing lesions on the tibial plafond (“kissing lesions”). Anterolateral osteochondral lesions are more likely to have a clear history of trauma than posteromedial lesions, although trauma probably plays a role in both.
Trauma may also set off pain in a previously asymptomatic arthritic ankle.
Clinical assessment
History taking aims to assess the frequency, severity and significance of episodes of giving way or pain, and to detect underlying problems such as arthritis and general joint laxity syndromes. An account of the original injury may help to understand the forces exerted on the ankle. The patient’s needs and expectations of the ankle for work, sports and other hobbies should be determined. It is useful to know if a personal injury claim is being pursued.
Check the overall limb and foot alignment. Hindfoot varus or pes cavus may predispose to recurrent ankle instability. If there is pes cavus need full neurological examination. Look for joint tenderness and synovitis. Spurs or osteophytes may be palpable. The Molloy test is accurate in detecting post-traumatic synovitis causing impingement. A similar test can be employed posteriorly, although its accuracy is not known. Tenderness over the talar dome may indicate an OCD lesion or arthritis. We emphasise clinical examination in detecting mechanical ankle instability, using the anterior draw and talar tilt tests. Swelling or tenderness in the sinus tarsi may indicate subtalar synovitis or a talocalcaneal ligament tear. Check for tendonopathy of the peroneal and long flexor tendons, and peroneal instability. Examine each of the major nerve trunks for tenderness, Tinel test or altered sensation.
Investigation
The Ottawa ankle rule is accurate in predicting the need for an Xray. If possible get Xrays of the ankle standing as this will show deformity and joint space loss better.
Stress radiographs of the ankle are of limited value unless taken using local or general anaesthesia and a jig which applies precise amounts of stress. In any case they do not alter the initial management. We do not recommend them in the initial management of ankle problems.
MR will show injuries to ligaments and tendons, OCD, bone bruising and fractures. Not all of these abnormalities are of clinical significance.
Ultrasound will show ligament and tendon injuries, possibly less accurately than MR, but it may be more available. It will show an effusion in the ankle joint.
Guidelines
- Patients with minor injuries should be given advice on self-care, the natural history of the injury and how to contact a physiotherapist if the injury fails to settle, by A+E or MIU staff.
- Patients with severe or recurrent injuries should be referred from A+E or MIU to physiotherapy
- Acute injuries should normally progress through phase 1 and 2 treatment in general physio and be referred for phase 3 rehab if indicated
- Acute injuries with persistent severe pain should have plain Xrays if indicated by the Ottawa rule; if this is normal or not indicated they should be considered for early MR to exclude OCD. Richard, Jo, FAS physios, Jim or Aamir should make the decision
- Patients with chronic problems will normally be offered phase 3 rehab initially. If they have significant synovitis or impingement it may be worth injecting the ankle with steroid before starting rehab.
- Patients who fail phase 3 treatment, or recur early, should be re-assessed for underlying problems such as biomechanical abnormality, arthritis, or general joint laxity, and their main problem defined.
- Biomechanical problems may be referred to the podiatrist
- If inflammatory arthritis is suspected standard investigations are FBC, ESR, U+E, urate and RA latex, plus HLA B-27 if spondyloarthropathy (psoriatic, anklylosing spondylitis, Reiters etc) suspected clinically
- Generalised joint laxity predicts a poor outcome from surgery; an ankle brace may be helpful but probably no other treatment
- For impingement an injection of depot steroid can be offered. If this gives a useful but transitory benefit a second injection, but usually no more, may be offered. Patients who derive only a short-lived benefit, or no benefit but with a positive Molloy test, can be offered arthroscopic debridement
- For persistent instability offer examination and stress views under anaesthesia with diagnostic arthroscopy. Often there will be post-traumatic synovitis which can be debrided and it may be unnecessary to stabilise the ankle. If there is proven mechanical instability a stabilisation can be offered, usually a Brostrom procedure (but if there proves to be insufficient tissue at surgery to repair, or if there is severe or very chronic instability or neuromuscular disease such as CMT, we would do a Sammarco anatomical tenodesis). Hindfoot varus or pes cavus should be corrected, normally at the same procedure.
- For non-impingement ankle pain obtain an MR (Richard, Jo, FAS physios, Jim or Aamir should make the decision). If OCD offer arthroscopic debridement. Recurrent pain after previous arthroscopic surgery should be reviewed by Jim or Aamir for possible osteochondral grafting.
- If MR shows bone oedema this will usually settle with time. There are some new treatments about for this – if severe or persistent may offer these.
- MR may show post-traumatic synovitis: manage as impingement
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